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Article

The Mechanism of Seed Priming with Abscisic Acid for Enhancing Cuticle Deposition Under Drought Stress: Phenotypic and Transcriptomic Insights

by
Luhua Yao
1,
Sennan Li
1,
Nana Zhou
1 and
Yanjun Guo
2,*
1
Department of Agriculture and Forestry, Hainan Tropical Ocean University, Sanya 572022, China
2
College of Grassland Science, Qingdao Agricultural University, Qingdao 266109, China
*
Author to whom correspondence should be addressed.
Agriculture 2025, 15(11), 1124; https://doi.org/10.3390/agriculture15111124
Submission received: 13 April 2025 / Revised: 11 May 2025 / Accepted: 13 May 2025 / Published: 23 May 2025
(This article belongs to the Section Seed Science and Technology)
Browse Figures
Versions Notes

Abstract

:
Plant cuticles are crucial for protecting plants from various environmental stresses. Seed priming with abscisic acid (ABA) enhances crop stress tolerance, but its molecular mechanisms in cuticular wax and cutin biosynthesis remain unclear. This study investigated ABA-priming’s role in boosting cuticular wax and cutin accumulation in sweet sorghum (Sorghum bicolor L.) using physiological and transcriptomic analyses. Abscisic acid priming increased leaf wax (37.7%) and cutin (25.6%) under drought, reducing water loss (9.8–36.6%) and improving leaf water content (28.4–120%). Transcriptomics identified 921 differentially expressed genes, including key fatty acid biosynthesis genes (ADH2, DES2, KAS2). Co-expression analysis revealed the synergistic regulation of wax and cutin biosynthesis by the abscisic acid and jasmonic acid (JA) pathways. Exogenous ABA and JA application confirmed their roles, with combined treatment increasing wax content by 71.7% under drought stress. These findings were validated in other sweet sorghum cultivars (DLS and ML8000), highlighting the potential of ABA priming as a universal strategy to enhance wax deposition in crops. Our study provides new insights into the molecular mechanisms underlying ABA-induced drought resistance and offers a practical approach for improving crop resilience in water-limited environments.

1. Introduction

Drought severely affects crop growth and yield all over the world. This is mainly attributed to insufficient rainfall and soil water during the growing season [1]. It has been reported that drought is responsible for at least 50% of losses in crop production throughout the world, and this proportion is dramatically increasing due to climate change [1,2]. Therefore, improving the acclimation ability of crop to drought stresses is crucial in increasing crop production.
Seed priming, a low-cost and low-risk pre-sowing method, is considered to be the most effective methods to enhance the germination parameters and seedling vigor under both optimal and adverse environmental conditions [3,4]. Previous studies have shown that water and polyethylene glycol (PEG) as osmoprimings are reliable methods of improving seed germination and stabilizing crop yield irrespective of plant species or development stages, particularly under unfavorable environmental conditions [5,6,7,8]. Hormone priming has also been widely used to improve seed germination, seedling growth, and the yield of a variety of crop species, such as wheat [9]. Seed soaking with abscisic acid (ABA) mitigated the harmful effects of water stress for Triticum aestivum [10]. Seed priming could improve protection against oxidative stress and retain memory of previous stresses [11,12]. Recently, Srivastava, Suresh Kumar, and Suprasanna [13] also stated that both seed priming and stress memory invoke a ‘bet-hedging’ strategy in plants. This might be attributed to the priming memory which enabled the plants to withstand stresses by adjusting the functions of key signaling molecules and transcription factors related to stresses [14]. A study on wheat has shown that seed priming improved the tissue water status and osmolyte accumulation, and thus the plant transgenerational drought tolerance [15]. The plant cuticle, as the outermost layer of a plant, plays pivotal roles in improving plant abilities to adapt to environmental stress conditions [16]. However, whether seed priming will alter the chemical compositions of plant cuticle, and if so, how much such alteration contributes to plant drought tolerance, is still unexplored.
In response to the varying environmental conditions, the plant cuticle can change and expand its structure and composition [17]. The integrity and permeability of the cuticle are very important for its function when resisting environmental stresses. For instance, a more complete structure and uniform distribution of plant cuticle could lead to resistance and viability to drought [18]. Plant cuticle comprises a matrix of cutin (an insoluble polyester) and embedded wax (soluble lipids), a complex mixture of very long chain fatty acids (VLCFAs) and their derivatives, such as aldehydes, alkanes, ketones, primary and secondary alcohols, esters, and triterpenoids, sterols, and phenolic compounds [19]. Studies have shown that cuticular wax protects plants against abiotic stresses such as drought, extreme temperatures, mechanical injuries, ultraviolet B (UV-B) radiation, and biotic stress such as chemical attack and pathogen/pest infection [19,20]. Treating plants with exogenous plant hormones increased the contents of wax and cutin components, which further decreased the leaf water loss during drought [21,22,23]. Increased leaf cuticular wax content was also observed in UV-B-primed seedlings of rice subjected to UV-B, NaCl, and PEG stresses [24]. However, it is still not clear whether seed priming can “remember” the pre-treatment and change the deposition of the cuticle during the following seedling growth, and thus be involved in plant drought tolerance.
ABA, which can be induced by drought, could promote the biosynthesis of alkanes (C29 and C31) [22], and ABA-treated plants have shown increased proportions of aliphatic components with chain lengths larger than C26 [22]. These results suggest that changes in ABA in plants may induce alterations of cuticle biosynthesis, and thus plant resistance to abiotic stresses. Seed priming with indole-3-acetic acid (IAA) resulted in enhanced seed germination and seedling growth in Gossypium hirsutum, along with favorable shifts in endogenous phytohormones including ABA [25]. Seed priming with SA promoted endogenous hormone metabolisms and signal transduction in maize seed [26]. Therefore, alterations of endogenous hormone metabolism might involve regulating cuticle biosynthesis.
To fill the gap between seed priming and seedling cuticle biosynthesis, seeds of sweet sorghum (Sorghum bicolor) were primed with ABA solution, and then we assessed cuticular waxes and transcriptomics on sweet sorghum seedlings subjected to drought stress, aiming to characterize the wax’s acclimation of sorghum seedlings primed by ABA, and to decipher the underlying mechanisms of cuticle synthesis induced by seed priming. Our findings will deepen the understandings of the mechanisms driving priming memory and provide valuable information for using cuticle to improve plant drought tolerance.

2. Materials and Methods

2.1. Plant Growth Conditions, Seed Priming Treatments, Stress Treatments, and Exogenous Hormone Treatments

The seeds of the inbred sorghum (Sorghum bicolor L.), P05206, were provided by the Institute of Sorghum Research, Shanxi Academy of Agricultural Science, China. Seeds of Hunnigreen (DLS) and ML8000 were hybrid sweet sorghum varieties. The seeds were sterilized in 3% H2O2 for 15 min and washed with distilled water to remove traces of the disinfectant, and then used for seed priming. The seeds were primed with ABA (10, 20, 30, 40, and 50 μg mL−1) or water at 20 °C in darkness for 24 h [27], and dried back to their original dry weight at room temperature.
Two pot experiments were conducted. In pot experiment one, there were four treatments, including control (CK), drought stress (Drought), ABA priming under well-watered conditions (ABA), and ABA priming under drought-stressed condition (ABA&D). CK: water-primed plants were under well-watered conditions with a relative water content of around 80% of the field capacity. Drought: water-primed plants in the third leaf stage were subjected to drought stress for 14 days with relative water content at 35% of the field capacity. ABA: ABA-primed plants were under well-watered conditions with a relative water content around 80% of the field capacity. ABA&D: ABA-primed plants in the third leaf stage were subjected to drought stress for 14 days with a relative water content at 35% of the field capacity. Water was supplemented every day to keep soil water content at required levels. Soil water content was calculated according to the weight and expressed as a percent maximum pot capacity.
In pot experiment two, the plants at the third leaf stage were subjected to drought stress with a soil relative water content at 35% of field capacity, then sprayed with 20 μg mL−1 ABA (or 5 μg mL−1 JA) at 9 AM daily consecutively for 14 days. The soil relative water contents of the control were kept at 75% of field capacity. Water was supplemented every day to keep the soil water content at the required levels.
The pot experiments were conducted in a glasshouse, with daytime temperatures maintained at 28 °C and nighttime temperatures at 20 °C. The relative air humidity during the experiment was 70%~80%, simulating crop field growth humidity. No artificial light was supplemented. The soil was a mixture of peat and arable soil (1:2), with a pH of 6.57, alkaline dispelled nitrogen at 85 mg kg−1, available phosphorus at 24 mg kg−1, and available potassium at 114 mg kg−1. Each treatment was replicated four times, with three plants in each pot.

2.2. Leaf Cuticle Composition and Structure Analysis

Leaf Cutin and Wax Extraction

Cutin extraction: Leaves from each replicate were immersed in solution of CHCl3: methanol (1:1) until the color of the leaves turned into white, and then were dried at 80 °C, and 0.03 g of the dried samples was extracted for 2 h with 2 mL methanol hydrochloride in a water bath at 80 °C, and then saturated salt water was added to terminate the reaction. n-Hexane containing 1 μg hexatriacontane as the internal standard was used to extract cutin [28].
Wax extraction: Leaves from each replicate were extracted for 10 s in 10 mL chloroform containing 1 μg tetracosane as the internal standard, and this was repeated three times. Before wax extraction, the surface areas of the leaves were measured with a WinFOLIA professional leaf image analysis system (Regent Instrument Inc., Quebec, QC, Canada) and a digitizing scanner (EPSON V750, Japan).
The cutin and wax extracts were dried under N2 at 40 °C, and derived using 20 μL pyridine and 20 μL BSTFA for 45 min at 70 °C [28]. The surplus BSTFA was evaporated under N2, and the sample was re-dissolved in 1 mL hexane for gas chromatography (GC) and gas chromatography–mass spectrometry (GC/MS) analysis.

2.3. GC/MS Analysis

The GC analysis was carried out with a 9790II gas chromatograph (Zhejiang Fuli Analytic Instruments Co., Taizhou, China). The GC column was DM-530 m × 0.32 mm × 0.25 μm capillary column (Dikma Technologies Inc., Markham, ON, USA). For each GC/MS run, 2 μL of the derivatized extract from the soil and leaf was injected. Helium was used as the carrier gas. The injector and flame ionization detector (FID) temperatures were set at 300 and 320 °C, respectively. The oven temperature of the GC was programmed with an original temperature of 80 °C and increased at 15 °C min−1 to 260 °C, where the temperature remained for 10 min. The temperature was then increased at 2 °C min−1 to 290 °C, and further increased at 5 °C min−1 to 320 °C, where the temperature remained for 10 min. Peaks were assigned by comparing of their mass spectra with the mass spectral library (GC/MS solution software, Shimadzu, Kyoto, Japan) [28].

2.4. Leaf Growth and Physiological Characteristic Analysis

2.4.1. Leaf Relative Water Content

The relative water content (RWC) was measured according to the method of Barrs and Weatherley [29]. Briefly, the first fully expanded leaves from the top were sampled and weighed immediately for the measurement of fresh weight (FW). Leaf saturated weight (SW) was determined after the leaf segments were immersed in distilled water for 3 h, dried at 70 °C in an oven for 24 h, and weighed for dry weight (DW). The relative water content (RWC) was calculated as follows:
RWC = (FW − DW)/(SW − DW) × 100%

2.4.2. Leaf Water Loss Rate

The plants were dark-acclimated for 12 h to ensure stomatal closure, and then the leaf samples were immersed in distilled water for 1 h and weighed. Next, the leaf samples were put into a dark chamber for continuous dehydration and their weights were determined in 15 min intervals for 150 min to record the water loss. Then, the leaf samples were dried at 70 °C for 24 h and weighed [28]. The water loss percentage was calculated as follows:
Water loss (%) = (saturated weight − fresh weight)/(saturated weight − dry weight) × 100%

2.5. Biomass Analysis

At the end of drought treatments, the shoots were harvested and dried in an oven at 70 °C for 72 h to determine the total dry weight.

2.6. RNA Quantification and Qualification

Four fully grown leaves from three plants in each treatment were pooled as one biological replicate for RNA-Seq analysis. All samples were immediately flash-frozen in liquid nitrogen after collection and stored at −80 °C until RNA extraction. Storage duration did not exceed 2 weeks to ensure RNA integrity. Three biological replicates were performed. RNA concentration and purity were measured using NanoDrop 2000 (Thermo Fisher Scientific, Wilmington, DE, USA). RNA integrity was assessed using the RNA Nano 6000 Assay Kit of the Agilent Bioanalyzer 2100 system (Agilent Technologies, Santa Clara, CA, USA). The clustering of the index-coded samples was performed on a cBot Cluster Generation System using TruSeq PE Cluster Kit v4-cBot-HS (Illumia, San Diego, CA, USA) according to the manufacturer’s instructions. Raw sequences were transformed into clean reads after data processing. These clean reads were then mapped to the reference genome sequence (Sorghum_bicolor v3.1.1). The DEGs of CK, ABA, D, and ABA&D-treated plants relative to the control samples were identified with a p < 0.05 and fold change = 1.5 or fold change < 0.5 as the threshold. Kyoto Encyclopedia of Genes [30] and Genomes (KEGG) pathway enrichment of DEGs [30] were performed using R (version 3.x), based on the hypergeometric distribution.

2.7. Quantitative Real-Time PCR Validation

RT-PCR was used to validate the RNA-seq data for selected candidate genes. Assays of each gene were repeated three times. Quantification was evaluated using the 2−(ΔΔCt) method. The primers used in this experiment are listed in Table S1.

2.8. Statistical Analysis

All values are presented as the mean ± SE. One-way ANOVA analysis was applied to compare the biomass, relative water content, leaf water loss rate, total contents of cuticular wax, and cutin between treatments (SPSS 17.0, Chicago, USA). Significance was tested according to the least significant difference test (LSD) at p < 0.05. Student’s t-tests were also conducted to assess the impact of a treatment compared to a control group.

3. Results

3.1. Seed Priming Improved Leaf Cuticular Wax Deposition and Drought Tolerance of Sorghum Seedlings

In a preliminary experiment, sweet sorghum seeds primed with ABA solutions (10 and 20 μg mL−1) were subjected to drought stress at the seedling stage (Supplemental Figure S1). ABA priming significantly increased total leaf wax content by 12.3–33.3% and plant biomass by 25–30%, with the highest improvement observed at 20 μg mL−1 ABA (Figure 1A,B). Under drought conditions, ABA-primed seedlings exhibited higher leaf total wax (37.7% increase) and biomass compared to unprimed seedlings.
Further analysis revealed that sorghum leaf cuticular waxes consisted of alkanes, alcohols (primary alcohol, simiarenol, and fernenol), aldehydes, and triterpenoids, while cutin was primarily composed of alkanoic acids, stearic acid, 2.6-oifluorobenzcic acid, and cyclopropaneoctanoic acid (Figure 1A,B). Drought stress significantly increased cutin content (1.3 times higher than well-watered conditions), but had no significant effect on total wax content. However, ABA priming under drought stress increased total wax and cutin contents by 37.7% and 25.6%, respectively, compared to unprimed seedlings (Figure 1A,B). ABA priming also reduced leaf water loss rate by 9.8–36.6% and improved leaf relative water content by 28.4–120% (Figure 1C,D). These results showed that the increased amount of cuticle waxes contributed to drought resistance.

3.2. ABA Priming Influenced Plant Cutin and Wax Biosynthesis

A transcriptomic analysis of sorghum leaves from plants in ABA, D, and ABA&D identified 481, 2225, and 2084 differentially expressed genes (DEGs) compared with CK, respectively (Supplemental Figure S2). Among the DEGs, 14 genes were annotated to cuticle biosynthesis pathways, including ADH2, DES2, and KAS2, which were uniquely induced by ABA priming under drought stress (Figure 2A,B and Table S1). Correlation analysis showed that DES2 and KAS2 were negatively correlated with the contents of α-amyrin (r = −0.82) and stearic acid (r = −0.75), respectively (Figure 2C,D). These results suggest that ABA priming enhances wax and cutin biosynthesis by regulating key genes in fatty acid metabolism.

3.3. Co-Expression Network Analysis Identified Photosynthesis and Wax-Related DEGs

Weighted gene co-expression network analysis (WGCNA) identified 10 modules, with the red and blue modules being positively correlated with wax and cutin components (Figure 3). An analysis of the module–trait relationships revealed that the red and blue were highly positively correlated and gray/green was highly negatively correlated with the different wax components, respectively. Specifically, the blue module was highly positively correlated with alcohol (p < 0.05), while the green module was highly negatively correlated with α-amyrin. Genes enriched in the red, blue, and green modules were more annotated as being photosynthetic, and their related pathways and hormone signal transductions showed that gene expression in these pathways is highly correlated with total wax, alcohol, and α-amyrin content.
KEGG enrichment analysis showed that the gene cluster the red module was annotated mainly in the photosynthesis processes, that in the green cluster was annotated in the hormone signal pathway, and that in the blue cluster was annotated in metabolite-related pathways such as that of flavonoid, fatty acid, and terpenoid synthesis (Supplementary Figure S3).

3.4. Co-Expression Network Analysis Identified Hormone- and Wax-Related DEGs

Hormone-related KEGG pathways, including ABA and JA, were enriched among DEGs (Figure 4 and Tables S3 and S4). We found that most genes related to the JA and ABA biosynthetic pathway showed increased and decreased expression under ABA&D treatment, respectively. Notably, the ABA priming markedly induced genes related to the JA and ABA biosynthetic pathway in comparison to D.
Representatively, in terms of genes involved in the ABA and JA signaling pathway, we noted the following: ABA priming upregulated PP2Cs, SnRK2s, and PYLs while downregulating JAZ proteins, indicating that ABA priming activated the JA signaling pathway combined with the ABA pathway to resist drought (Figure 4B,D). These results suggest that ABA and JA signaling synergistically regulate wax and cutin biosynthesis under drought stress. Exogenous application of ABA and JA under drought condition further confirmed their roles in promoting wax deposition, with combined treatment increasing total wax content by 71.7% (Figure 5).

3.5. Verification Using Other Sweet Sorghum Cultivars (DLS and ML8000)

To further study the role of ABA priming in the response of other sweet sorghum plants to the drought stress, we performed a parallel pot experiment for ML8000 and DLS. The results confirmed that ABA priming increased cuticular wax content by 12.3–33.3%, leaf relative water content by 28.4–120%, and drought tolerance (Figure 6). Similar to P05206, plants with ABA seed priming treatment prior to exposure to drought stress showed drought tolerance, with higher cuticle wax content and leaf relative water content, and lower leaf water loss rate relative to plants without the ABA priming pre-treatment. These results strengthen the suggestion that ABA seed priming might play a key role by increasing leaf cuticle wax content in the acclimation of sorghum seeding under drought stress.

4. Discussion

4.1. Seed Priming with ABA Influenced Endogenous Hormone Accumulation

Previous studies have shown that ABA is a plant stress hormone which accumulates under the application of exogenous ABA and drought stress [31,32]. NCED, which encodes a key enzyme in the biosynthesis of abscisic acid, was up-regulated in expression by exogenous ABA and drought stress [33]. In this study, the expression of the ZEP and NCED1 genes was significantly increased and the content of ABA also increased in both ABA&D and drought-stress treatment. These results indicated that seed priming with ABA could improve ABA accumulation in the same way as exogenous ABA.

4.2. Seed Priming with ABA Improved Cuticle Tolerance by Endogenous Hormone Adjustment Under Drought Conditions

Lipid-mediated defenses against environmental stress contributes to plant survival [34]. Wax and cutin are components derived from lipids, which coats the aerial surfaces of plants and limits water loss through non-stomatal transpiration contributing to the reduction in drought stress and tissue injury [24]. In this study, the content of wax and cutin were significantly increased and the non-stomatal water loss rate was reduced by seed priming with ABA, indicating cuticle drought tolerance improved by seed priming with ABA. Plants adjust wax depositions and wax compositions such as alkanes, alcohol, and aldehyde to minimize cellular and organismal dehydration under drought conditions [28,35,36]. In this study, the amounts of long-chain alkanes (C31–C33) and triterpenoids also increased in ABA-primed seedlings under drought conditions, suggesting that seed priming with ABA mainly promoted very-long-chain fatty acid elongation and triterpenoid accumulation to reduce leaf water loss. Similarly, the increased content of C18 unsaturated acids, not C18 saturated acid, under drought conditions contributed to improved plant drought tolerance [37]. In this study, content of C18 unsaturated acids increased and the content of C18 saturated acid reduced. These results indicated that seed priming with ABA might alter the biosynthesis of cutin and wax and at the seedling stage, resulting in decreased leaf water loss under drought conditions and improved drought tolerance.
Our transcriptome data indicated that of unique DEGs induced by seed priming with ABA, some adjusted wax and cutin biosynthesis, including in biosynthesis from acyl-CoA to long chain acyl-CoA elongation, to long fatty acid, and to wax and cutin. Among these genes, the overexpression of CER1 could increase the content of alkanes [18,38]. In this study, the expression of CER1-1 in ABA-primed seedlings increased under drought conditions and drought-stressed seedlings. DES2 related to fatty acid desaturase [39], and KAS2, LACS1, and CUT1 related to long chain fatty acid [40,41,42], were uniquely induced by seed priming with ABA under drought conditions. CUT1/CER6 is the key condensing enzyme for wax biosynthesis in Arabidopsis [43]. Overall, we conclude that seed priming with ABA contributes to the wax and accumulation by activating the key synthesis genes. Previous studies have shown that drought stress results in the increased production of cuticular waxes [44]. We also observed that these genes in wax and the cutin biosynthesis pathway were further differentially expressed in ABA-primed plants more than drought-stressed plants, indicating that seed priming with ABA has a superposition effect on wax and cutin synthesis. These results imply that seed priming with ABA might produce a priming ‘memory’, contributing to their expression under drought stress [45,46].
WGCNA between cuticle components and hormone pathways showed that the expression of the key genes in JA biosynthesis and ABA signaling transduction (PP2Cs, SnRK2, and PYLs) induced by seed priming with ABA were highly correlated with wax and cutin components. These results demonstrated that ABA and JA induced by ABA-priming influenced wax and cutin biosynthesis at the transcription level. This, combined with the different changes in ABA and JA in ABA-primed plants under drought conditions, implied that JA and ABA might activate different genes involved in cuticular wax and cutin biosynthesis under drought conditions [47,48]. To further prove whether the increase in JA and JA-Ile in sorghum seedlings would increase the wax depositions, a parallel exogenous ABA and JA application experiment was conducted. The results showed that the exogenous ABA and JA promoted the amount of cuticular wax. Therefore, we suggest that the endogenous hormone, which was influenced by seed priming with ABA, might be important for wax biosynthesis, contributing to plant drought tolerance. Additionally, the relative contributions of ABA-dependent versus ABA-independent JA pathways require further investigation.

5. Conclusions

Through the transcriptomic and exogenous hormone experiment under drought stress, we have revealed the drought mechanisms of the cuticle tolerance in sorghum seedlings pre-primed with ABA. We suggest that seed priming with ABA positively regulates transcriptional control, and activates both ABA and JA signals to adjust the biosynthesis of long chain fatty acids. The exogenous hormone experiment proved that seed priming with ABA activated JA and ABA signals, which further adjusted leaf cuticle biosynthesis. This study contributes to a deeper understanding of the sophisticated and efficient mechanisms of ABA priming in the response of plants to drought stress at the seedling stage and, consequently, provides an effective method of improving crop drought tolerance in agricultural production. However, since these findings are based on a single growing season and a single crop species, future studies should expand to multiple environments and crop species (e.g., different climatic zones, interannual trials) to evaluate how wax dynamics are influenced by interactions between drought and other abiotic factors (e.g., temperature extremes, UV radiation, and humidity fluctuations). Such investigations will further clarify the robustness of ABA priming as a climate-resilient strategy for crop improvement.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/agriculture15111124/s1. Figure S1: The effect of seed priming with ABA on sorghum biomass and total wax content. A: An illustration of sorghum developmental stage, seed priming and stress strategy, and sampling time points. Control plants were grown under optimal conditions throughout the experiment. Drought was gradually applied by withholding irrigation. B: The total wax content in ABA-primed seedlings. C: Sorghum biomass of ABA-primed seedlings. D: The total wax content of seedlings primed at 20 μg mL−1 ABA. E: Sorghum biomass of seedlings primed at 20 μg mL−1 ABA. The data were the mean ± SE (n = 4). Different lowercase letters (p < 0.05) and ‘*’ (*, 0.01 < p < 0.05; **, 0.001 < p < 0.01; ***, p < 0.001; ns, no significant difference) represented significant differences between treatments according to least significant difference test. Figure S2: Global transcriptome responses of sorghum to ABA priming and drought stress. (a) The number of DEGs under ABA priming (ABA), drought stress (D), and combined treatment (ABA&D). (b) Venn diagrams of DEGs. Figure S3: KEGG enrichment of different modules in WGCNA. The figure shows the first 20 pathways of the different modules. Figure S4: qPCR expression-level validation of DEGs using qRT-PCR in comparison to corresponding data detected in RNA-Seq. The bar chart represents data of qRT-PCR. Scatter plot represents data of RNA-Seq. To confirm the RNA-seq data, we assessed the expression of 7 DEGs using quantitative real-time PCR (Q-PCR). As shown in Fig S4, the Q-PCR data were consistent with the RNA-seq data, and a similar expression trend in different samples supports the reliability of the RNA-seq data. Table S1: The primer sequence and Tm of DEGs involved in Q-PCR. Table S2: The uniquely induced DEGs in enriched KEGG pathways of seed priming with ABA under drought-stressed conditions (ABA&D) and commonly induced by both ABA&D and drought without seed priming (D). Table S3: The expression pattern of DEGs related to hormone biosynthesis of uniquely induced DEGs in seed priming with ABA under drought-stressed conditions (ABA&D) and common DEGs in both ABA&D and drought without seed priming (D). DEGs were identified with an FDR < 0.05 and fold change > 1.5 as the threshold. Table S4: The expression pattern of DEGs related to hormone signal transduction of uniquely induced DEGs in seed priming with ABA under drought-stressed conditions (ABA&D) and common DEGs in both ABA&D and drought without seed priming (D). DEGs were identified with an FDR < 0.05 and fold change > 1.5 as the threshold.

Author Contributions

Conceptualization, Y.G.; methodology, L.Y. and S.L.; investigation, S.L.; writing—original draft preparation, L.Y. and N.Z.; writing—review and editing, L.Y. and Y.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Scientific Research Foundation of Hainan Tropical Ocean University (RHDRC202318).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The transcriptomic sequencing data analyses were based on clean data of high quality, and all row data generated in this study are accessible at the National Center for Biotechnology Information (NCBI) under the accession number (BioProject accession No. PRJNA742228).

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
ABAabscisic acid
DLSHunnigreen
ML8000Mule8000
CKcontrol
Ddrought stress
ABAabscisic acid
JAJasmonic acid
GCGas chromatography
MSMass Spectrometry
FIDflame ionization detector
RWCrelative water content
FWfresh weight
SWsaturated weight
DEGsdifferentially expressed genes
KEGGKyoto Encyclopedia of Genes and Genomes
DWdry weight
WGCNAWeighted gene co-expression network analysis
qRT-PCRQuantitative real-time PCR

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Figure 1. The effects of seed priming with ABA on contents of leaf total cuticular wax and wax composition (A), contents of leaf total cutin and cutin composition (B), the leaf water loss rate (%) (C), and leaf relative water content (RWC) (%) (D). The data are the mean ± SE (n = 4). Different lowercase letters within same parameters among different treatments represented significance according to the least significant difference test (p < 0.05). CK, control; D, drought without seed priming; ABA, seed priming with ABA under well-watered conditions, and ABA&D seed priming with ABA under drought-stressed conditions. uk in Figure 1A: unknown wax components. *, 0.01 < p < 0.05; ***, p < 0.001; ns, no significant difference.
Figure 1. The effects of seed priming with ABA on contents of leaf total cuticular wax and wax composition (A), contents of leaf total cutin and cutin composition (B), the leaf water loss rate (%) (C), and leaf relative water content (RWC) (%) (D). The data are the mean ± SE (n = 4). Different lowercase letters within same parameters among different treatments represented significance according to the least significant difference test (p < 0.05). CK, control; D, drought without seed priming; ABA, seed priming with ABA under well-watered conditions, and ABA&D seed priming with ABA under drought-stressed conditions. uk in Figure 1A: unknown wax components. *, 0.01 < p < 0.05; ***, p < 0.001; ns, no significant difference.
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Figure 2. Seed priming with ABA influenced the fatty acid biosynthesis. (A) The expression profile of transcripts uniquely induced by ABA&D. The value is the log2 fold change (log2(FC)) of each gene. (B) The expression profile of common transcripts induced by ABA&D and D. The heatmap is the clustering of the log2 fold change (log2(FC)) of each gene. The colors of the boxes represented upregulated (red) and downregulated (green) genes. (C) The Pearson correlation analysis between DEGs related to fatty acid biosynthesis, wax, and cutin compositions. The number was correlation coefficient and ‘*’ represented significant difference (p < 0.05). The value is the log2 fold change (log2(FC)) of each gene. The colors of the boxes represented positive correlation (red) and negative correlation (blue). WZ: unknown components. (D) A diagrammatic sketch of the synthesis process of cuticle components involved the DEGs.
Figure 2. Seed priming with ABA influenced the fatty acid biosynthesis. (A) The expression profile of transcripts uniquely induced by ABA&D. The value is the log2 fold change (log2(FC)) of each gene. (B) The expression profile of common transcripts induced by ABA&D and D. The heatmap is the clustering of the log2 fold change (log2(FC)) of each gene. The colors of the boxes represented upregulated (red) and downregulated (green) genes. (C) The Pearson correlation analysis between DEGs related to fatty acid biosynthesis, wax, and cutin compositions. The number was correlation coefficient and ‘*’ represented significant difference (p < 0.05). The value is the log2 fold change (log2(FC)) of each gene. The colors of the boxes represented positive correlation (red) and negative correlation (blue). WZ: unknown components. (D) A diagrammatic sketch of the synthesis process of cuticle components involved the DEGs.
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Figure 3. Module–trait relationships in WGCNA. an, alkanes; ol, alcohol; al, aldehyde, amyrin, α-amyrin; WZ, unknown cyclic compound; alkan, alkanoic acid; stearic, stearic acid; oifluo, 2.6-oifluorobenzcic acid; cyclo, cyclopropaneoctanoic acid.
Figure 3. Module–trait relationships in WGCNA. an, alkanes; ol, alcohol; al, aldehyde, amyrin, α-amyrin; WZ, unknown cyclic compound; alkan, alkanoic acid; stearic, stearic acid; oifluo, 2.6-oifluorobenzcic acid; cyclo, cyclopropaneoctanoic acid.
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Figure 4. The effects of seed priming with ABA on hormone biosynthesis and signal pathway genes. (A) The expression profile of transcripts involved in hormone biosynthesis and uniquely induced by ABA&D. (B) The expression profile of transcripts involved in hormone signal pathway and uniquely induced by ABA&D. (C) The expression profile of transcripts involved in hormone biosynthesis and commonly induced in ABA&D and D. (D) The expression profile of transcripts involved in hormone signal pathway and commonly induced in ABA&D and D. The value was the log2 fold change (log2(FC)) of each gene.
Figure 4. The effects of seed priming with ABA on hormone biosynthesis and signal pathway genes. (A) The expression profile of transcripts involved in hormone biosynthesis and uniquely induced by ABA&D. (B) The expression profile of transcripts involved in hormone signal pathway and uniquely induced by ABA&D. (C) The expression profile of transcripts involved in hormone biosynthesis and commonly induced in ABA&D and D. (D) The expression profile of transcripts involved in hormone signal pathway and commonly induced in ABA&D and D. The value was the log2 fold change (log2(FC)) of each gene.
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Figure 5. Effects of exogenous ABA, JA, and ABA&JA application on physiological responses of sweet sorghum under drought conditions. The data are the mean ± SE (n = 3). *, 0.01 < p < 0.05; ***, p < 0.001; ns, no significant difference. CK, control; D, drought without seed priming; ABA&D or (JA&D), seed priming with ABA or (JA) under drought condition, and ABA&&JAD, seed priming with ABA and JA under drought-stressed conditions. uk: unknown components.
Figure 5. Effects of exogenous ABA, JA, and ABA&JA application on physiological responses of sweet sorghum under drought conditions. The data are the mean ± SE (n = 3). *, 0.01 < p < 0.05; ***, p < 0.001; ns, no significant difference. CK, control; D, drought without seed priming; ABA&D or (JA&D), seed priming with ABA or (JA) under drought condition, and ABA&&JAD, seed priming with ABA and JA under drought-stressed conditions. uk: unknown components.
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Figure 6. Effects of seed priming with ABA on cuticular wax deposition and water loss rate of sweet sorghum cv. ML8000 (ML) and DLS. CK, control; D, drought without seed priming; ABA, seed priming with ABA under well-watered conditions; and ABA&D, seed priming with ABA under drought-stressed conditions. **, 0.001 < p < 0.01; ***, p < 0.001; ns, no significant difference.
Figure 6. Effects of seed priming with ABA on cuticular wax deposition and water loss rate of sweet sorghum cv. ML8000 (ML) and DLS. CK, control; D, drought without seed priming; ABA, seed priming with ABA under well-watered conditions; and ABA&D, seed priming with ABA under drought-stressed conditions. **, 0.001 < p < 0.01; ***, p < 0.001; ns, no significant difference.
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Yao, L.; Li, S.; Zhou, N.; Guo, Y. The Mechanism of Seed Priming with Abscisic Acid for Enhancing Cuticle Deposition Under Drought Stress: Phenotypic and Transcriptomic Insights. Agriculture 2025, 15, 1124. https://doi.org/10.3390/agriculture15111124

AMA Style

Yao L, Li S, Zhou N, Guo Y. The Mechanism of Seed Priming with Abscisic Acid for Enhancing Cuticle Deposition Under Drought Stress: Phenotypic and Transcriptomic Insights. Agriculture. 2025; 15(11):1124. https://doi.org/10.3390/agriculture15111124

Chicago/Turabian Style

Yao, Luhua, Sennan Li, Nana Zhou, and Yanjun Guo. 2025. "The Mechanism of Seed Priming with Abscisic Acid for Enhancing Cuticle Deposition Under Drought Stress: Phenotypic and Transcriptomic Insights" Agriculture 15, no. 11: 1124. https://doi.org/10.3390/agriculture15111124

APA Style

Yao, L., Li, S., Zhou, N., & Guo, Y. (2025). The Mechanism of Seed Priming with Abscisic Acid for Enhancing Cuticle Deposition Under Drought Stress: Phenotypic and Transcriptomic Insights. Agriculture, 15(11), 1124. https://doi.org/10.3390/agriculture15111124

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