Search Results (98)

The novel hydro-electro hybrid priming (HEHP) technique, which synergistically combines controlled hydration and electrostatic field application, represents an innovative chemical-free approach to improve seed germination synchrony. However, the regulatory mechanism of HEHP on cell wall remodeling during post-imbibition remains unclear. Here, we demonstrate that HEHP accelerates carrot (Daucus carota L.) seed germination by synchronizing cell wall hydrolysis and synthesis pathways. Comparative transcriptomics revealed 4591 differentially expressed genes (DEGs) between HEHP-treated and untreated seeds, with significant enrichment in cell wall organization (GO terms) and phenylpropanoid biosynthesis (KEGG pathway). HEHP significantly induced the expression of expansin (EXP), hydrolases (xyloglucan endotransglucosylase (XET), pectinesterase (PE), and phenylalanine ammonia lyase (PAE)), and synthases (cellulose synthase (CesA)), reducing endosperm rupture force considerably at S20 compared to hydropriming (HYD). Enzymatic assays confirmed earlier activity peaks for XET and PE in HEHP, correlating with the sustained expression of key genes. Notably, HEHP pre-activated germination-related metabolism, evidenced by fewer post-imbibition DEGs, and synchronized lignin deposition via transient phenylalanine ammonia lyase (PAL) and 4-coumarate/CoA ligase (4CL) activation. These synergies enabled faster radicle emergence than HYD. Our findings reveal that HEHP optimizes cell wall loosening–reinforcement dynamics through transcriptional priming, offering a tailored solution for mechanized sowing in Apiaceae crops. Full article

Expansins are cell wall-modifying proteins that play a pivotal role in plant growth, development, and stress adaptation to abiotic stress. This manuscript explores the functions of expansins in salt and drought stress responses across multiple plant species, highlighting their involvement in cell wall loosening, transcriptional regulation, ion and osmotic homeostasis, and phytohormone signalling. Genome-wide identification and expression analyses revealed differential regulation of expansin genes under abiotic stress conditions. In Nicotiana tabacum, overexpression of NtEXPA4 and NtEXPA11 promoted root elongation and ion homeostasis, improving salt and drought tolerance. Similarly, Brassica rapa BrEXLB1 was found to modulate root architecture and phytohormone-mediated stress responses. In Oryza sativa, OsEXPA7 was linked to cation exchange and auxin signalling under salt stress conditions. Conversely, in Populus trichocarpa, PtEXPA6 exhibited a negative regulatory role in salt stress tolerance, highlighting species-specific differences in expansin function. Expansins also contribute to reactive oxygen species (ROS) homeostasis, as observed in transgenic plants with increased activities of SOD, POD, APX, and CAT, which reduced oxidative damage under stress. Additionally, enhanced accumulation of soluble sugars and proline in expansin-overexpressing plants suggests their involvement in osmotic adjustment mechanisms. The interplay between expansins and ABA, auxins, and ethylene further underscores their role in integrating mechanical and hormonal stress responses. Despite substantial progress, limitations remain in understanding the broader regulatory networks influenced by expansins. Future research should focus on elucidating their downstream molecular targets, transcriptional interactions, and functional diversity across different plant species. Expansins represent promising candidates for improving crop resilience to environmental stress, making them valuable targets for future breeding and biotechnological approaches. Full article

Currently, developing cotton cultivation in saline–alkali soils is a vital focus for restructuring the cotton industry in China. The seedling stage, specifically the three-leaf stage, is a crucial period for assessing the salt tolerance of cotton. This research examined 430 natural populations of upland cotton, including 45 semi-wild germlines of Gossypium purpurascens. We measured the phenotypic responses of salt stress injury on seedlings as well as potassium (K), calcium (Ca), sodium (Na), and magnesium (Mg) concentrations in the roots, stems, and leaves following a 72 h exposure. The comprehensive salt tolerance index (CSTI) was determined using a membership function, principal component analysis, and cluster analysis based on 48 phenotypic traits related to salt tolerance. The results revealed significant variations in the phenotypic traits of the ion group under salt stress. Salt stress greatly affected the relative contents of Mg, K, and Ca ions in the aboveground parts of cotton, and correlations were observed among the 48 indices. The CSTI was calculated using seven principal component indexes, identifying 30 salt-tolerant, 114 weakly salt-tolerant, 39 salt-sensitive, and 4 highly sensitive materials based on cluster analysis. Among the 45 G. purpurascens cotton resources, 28 were weakly salt-tolerant, while 17 were salt-sensitive. Through TMT (Tandem Mass Tag)-based quantitative analysis, we identified 3107 unique peptides among 28,642 detected peptides, resulting in 203,869 secondary mass spectra, with 50,039 spectra successfully matched to peptides. Additionally, we identified several salt tolerance-related pathways (carbon metabolism; glutathione metabolism; the biosynthesis of amino acids, etc.) and proteins classified within the CAZy (Carbohydrate-Active EnZYme) family and expansin proteins. The results of this study concerning salt-tolerant materials provide a crucial theoretical foundation for the identification and evaluation of salt-tolerant breeding parents in cultivated cotton. Full article

Cell wall extensibility is a key biophysical characteristic that defines the rate of plant cell growth. It depends on the wall structure and is controlled by numerous proteins that cut and/or (re)form links between the wall constituents. Cell wall extensibility is currently estimated by different in vitro biomechanical tests. We used the creep method, in which isolated cell walls are extended under a constant load and their time-dependent deformation (creep) is recorded to reveal the biophysical basis of growth inhibition of Arabidopsis thaliana hypocotyls in the presence of 24-epibrassinolide (EBL), one of the most active natural brassinosteroids. We found that EBL rendered the walls of hypocotyl cells softer, i.e., more deformable under mechanical force, which was revealed using heat-inactivated cell walls to eliminate endogenous activities of cell-wall-loosening/tightening proteins. This effect was caused by the altered arrangement of cellulose microfibrils. At the same time, EBL made the walls less extensible, which was detected with native walls under conditions optimized for activities of endogenous cell-wall-loosening proteins. These apparently conflicting changes in the wall mechanics can be an adaptation by which EBL enables plant cells to grow under stress conditions. Full article

The basidiomycete Crucibulum laeve strain LE-BIN1700 (Agaricales, Nidulariaceae) is able to grow on agar media supplemented with individual components of lignocellulose such as lignin, cellulose, xylan, xyloglucan, arabinoxylan, starch and pectin, and also to effectively destroy and digest birch, alder and pine sawdust. C. laeve produces a unique repertoire of proteins for the saccharification of the plant biomass, including predominantly oxidative enzymes such as laccases (family AA1_1 CAZymes), GMC oxidoreductases (family AA3_2 CAZymes), FAD-oligosaccharide oxidase (family AA7 CAZymes) and lytic polysaccharide monooxygenases (family LPMO X325), as well as accompanying acetyl esterases and loosenine-like expansins. Metabolomic analysis revealed that, specifically, monosaccharides and carboxylic acids were the key low molecular metabolites in the C. laeve culture liquids in the experimental conditions. The proportion of monosaccharides and polyols in the total pool of identified compounds increased on the sawdust-containing media. Multiple copies of the family AA1_1, AA3_2, AA7 and LPMOs CAZyme genes, as well as eight genes encoding proteins of the YvrE superfamily (COG3386), which includes sugar lactone lactonases, were predicted in the C. laeve genome. According to metabolic pathway analysis, the litter saprotroph C. laeve can catabolize D-gluconic and D-galacturonic acids, and possibly other aldonic acids, which seems to confer certain ecological advantages. Full article

Saline–alkali environments restrict soybean production in China. Wild soybean genes can be used to improve the alkaline tolerance of cultivated soybean in molecular breeding. The expansin protein family promotes cell wall expansion. In this study, the relative expression levels of expansin family genes in wild soybean treated with 50 mM NaHCO₃ were measured at 0, 3, 6, and 12 h, and the relative expression of GsEXPA8 was found to be higher at 12 h. Wild soybean was treated with abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellic acid (GA), and jasmonic acid (JA), and GsEXPA8 was found to respond to ABA and IAA signals. Sequence analysis shows that GsEXPA8 has DPBB_EXPA and expansin domains. Subcellular localization analysis shows that GsEXPA8 was localized in the cytoplasm in protoplasts and the cell membrane or wall in tobacco, indicating that it has nuclear membrane localization signals. GsEXPA8 overexpression reduced the malondialdehyde content in transgenic plants treated with NaHCO₃ and increased peroxidase activity before treatment. After the transformation of soybean roots from hair roots, GsEXPA8 was found to be expressed in the outer root cells and promote the development of thicker, shorter roots, thereby improving the plant’s alkaline tolerance. Stable GsEXPA8 transformation improved saline alkaline tolerance via the regulation of the alkali stress-related genes GmKIN1, GmRD22, GmDnaJA6, GmNFYC1, and GmMYB14. These findings provide support for further research on alkali-tolerance regulation pathways and molecular breeding for alkali tolerance. Full article

All multicellular organisms undergo senescence, but the continuous division of the vascular cambium in plants enables certain tree species to survive for hundreds or even thousands of years. Previous studies have focused on the development of the vascular cambium, but the mechanisms regulating age-related changes remain poorly understood. This study investigated age-related changes in the vascular cambium of P. euphratica trees aged 50 to 350 years. The number of cambium cells in the 50-year-old tree group was 10 ± 2, while the number of cambium cells in the 200-year-old and 350-year-old tree groups significantly decreased. The thickness of the cambium cells exhibited a similar trend. In addition, the net photosynthetic and transpiration rates continue to increase with age, but no notable differences were found in factors like average leaf area, palisade tissue thickness, and stomatal density. A total of 6491 differentially expressed genes (DEGs) were identified in the vascular cambium of P. euphratica at three distinct ages using RNA sequencing. The expression patterns of DEGs associated with cell division and differentiation, lignin biosynthesis, plant hormones, and transcription factors were analyzed. DEGs related to XTH, EXP, PAL, C4H, ABA, Br, GA, and others are highly expressed in older trees, whilst those encoding expansins, kinases, cyclins, 4CL, Auxin, Eth, SA, and others are more prevalent in younger trees. Gene family members, such as NAC, MYB, HD-ZIP III, WRKY, and GRF, have various regulatory functions in the vascular cambium. The findings offer insights into how ancient P. euphratica trees maintain vitality by balancing growth and aging, providing a foundation for future research on their longevity mechanisms. Full article

The Xyloglucan endotransglucosylase/hydrolase (XTH) family, a group of cell wall-modifying enzymes, plays crucial roles in plant growth, development, and stress adaptation. The quality and yield of Chinese jujube (Ziziphus jujuba) fruit are significantly impacted by environmental stresses, including excessive salinity, drought, freezing, and disease. However, there has been no report of the XTH encoding genes present in the Chinese jujube genome and their response transcription level under various stresses. This study provides an in-depth analysis of ZjXTH genes in the genome of Chinese jujube and elucidates their structural motifs, regulatory networks, and expression patterns under various stresses. A total of 29 ZjXTH genes were identified from the Ziziphus jujuba genome. Phylogenetic analysis classifies ZjXTH genes into four distinct groups, while conserved motifs and domain analyses reveal coordinated xyloglucan modifications, highlighting key shared motifs and domains. Interaction network predictions suggest that ZjXTHs may interact with proteins such as Expansin-B1 (EXPB1) and Pectin Methylesterase 22 (PME22). Additionally, cis-regulatory element analysis enhances our understanding of Chinese jujube plant’s defensive systems, where TCA- and TGACG-motifs process environmental cues and orchestrate stress responses. Expression profiling revealed that ZjXTH1 and ZjXTH5 were significantly upregulated under salt, drought, freezing, and phytoplasma infection, indicating their involvement in biotic and abiotic stress responses. Collectively, these findings deepen our understanding of the functional roles of Chinese jujube XTHs, emphasizing their regulatory function in adaptive responses in Chinese jujube plants. Full article

This study investigates the molecular mechanisms underlying fruit cracking in Akebia trifoliata, a phenomenon that significantly impacts fruit quality and marketability. Through comprehensive physiological, biochemical, and transcriptomic analyses, we identified key changes in cell wall components and enzymatic activities during fruit ripening. Our results revealed that ventral suture tissues exhibit significantly elevated activities of polygalacturonase (PG) and β-galactosidase compared to dorsoventral line tissues, indicating their crucial roles in cell wall degradation and structural weakening. The cellulose content in VS tissues peaked early and declined during ripening, while DL tissues maintained relatively stable cellulose levels, highlighting the importance of cellulose dynamics in fruit cracking susceptibility. Transcriptomic analysis revealed differentially expressed genes (DEGs) associated with pectin biosynthesis and catabolism, cell wall organization, and oxidoreductase activities, indicating significant transcriptional regulation. Key genes like AKT032945 (pectinesterase) and AKT045678 (polygalacturonase) were identified as crucial for cell wall loosening and pericarp dehiscence. Additionally, expansin-related genes AKT017642, AKT017643, and AKT021517 were expressed during critical stages, promoting cell wall loosening. Genes involved in auxin-activated signaling and oxidoreductase activities, such as AKT022903 (auxin response factor) and AKT054321 (peroxidase), were also differentially expressed, suggesting roles in regulating cell wall rigidity. Moreover, weighted gene co-expression network analysis (WGCNA) identified key gene modules correlated with traits like pectin lyase activity and soluble pectin content, pinpointing potential targets for genetic manipulation. Our findings offer valuable insights into the molecular basis of fruit cracking in A. trifoliata, laying a foundation for breeding programs aimed at developing crack-resistant varieties to enhance fruit quality and commercial viability. Full article

The cell wall is a crucial feature that allows ancestral streptophyte green algae to colonize land. Expansin, an extracellular protein that mediates cell wall loosening in a pH-dependent manner, could be a powerful tool for studying cell wall evolution. However, the evolutionary trajectory of the expansin family remains largely unknown. Here, we conducted a comprehensive identification of 2461 expansins across 64 sequenced species, ranging from aquatic algae to terrestrial plants. Expansins originated in chlorophyte algae and may have conferred the ability to loosen cell walls. The four expansin subfamilies originated independently: α-expansin appeared first, followed by β-expansin, and then expansin-like A and expansin-like B, reflecting the evolutionary complexity of plant expansins. Whole genome duplication/segmental duplication and tandem duplication events greatly contributed to expanding the expansin family. Despite notable changes in sequence characteristics, the intron distribution pattern remained relatively conserved among different subfamilies. Phylogenetic analysis divided all the expansins into five clades, with genes from the same subfamily tending to cluster together. Transcriptome data from 16 species across ten lineages and qRT-PCR analysis revealed varying expression patterns of expansin genes, suggesting functional conservation and diversification during evolution. This study enhances our understanding of the evolutionary conservation and dynamics of the expansin family in plants, providing insight into their roles as cell wall-loosening factors. Full article

Expansins are known as cell wall loosening proteins and are involved in cell expansion and varieties of plant developmental progresses. However, little is known about their biological functions in alfalfa (Medicago sativa L.). In the present study, 30 MsEXP genes were identified in the alfalfa (cultivar “zhongmu-1”) genome. Phylogenetic analysis revealed that these MsEXP proteins were divided into four subfamilies, including twenty-one MsEXPAs, six MsEXPBs, one MsEXL1 and two MsEXLBs. MsEXP genes were unevenly distributed on eight chromosomes. The gene structures of the MsEXP genes and the motif composition of the MsEXP proteins were inconsistent with the phylogenetic relationship of MsEXPs. Cis-acting elements analysis indicated that MsEXP genes may respond to diverse hormonal signals involved in the developmental progress of plants. Furthermore, expression analysis suggested that MsEXP genes exhibited distinct expression patterns among different tissues of alfalfa. Overexpression of MsEXPA3 or MsEXPA4 promoted the growth of leaves, stems and roots of Arabidopsis, thereby increasing the biomass of plants. Subsequent cell morphological analysis uncovered that overexpression of MsEXPA3 or MsEXPA4 promoted the expansion of cells. Taken together, these findings illustrate the functions of MsEXP proteins in regulating the development of plants. Our results may provide a strong basis for further elucidating the roles of these EXP genes in alfalfa development and valuable genetic resources for future crop improvement. Full article

In the context of crop breeding, plant height (PH) plays a pivotal role in determining straw and grain yield. Although extensive research has explored the genetic control of PH in wheat, there remains an opportunity for further advancements by integrating genomics with growth-related phenomics. Our study utilizes the latest genome-wide association scan (GWAS) techniques to unravel the genetic basis of temporal variation in PH across 179 Bulgarian bread wheat accessions, including landraces, tall historical, and semi-dwarf modern varieties. A GWAS was performed with phenotypic data from three growing seasons, the calculated best linear unbiased estimators, and the leveraging genotypic information from the 25K Infinium iSelect array, using three statistical methods (MLM, FarmCPU, and BLINK). Twenty-five quantitative trait loci (QTL) associated with PH were identified across fourteen chromosomes, encompassing 21 environmentally stable quantitative trait nucleotides (QTNs), and four haplotype blocks. Certain loci (17) on chromosomes 1A, 1B, 1D, 2A, 2D, 3A, 3B, 4A, 5B, 5D, and 6A remain unlinked to any known Rht (Reduced height) genes, QTL, or GWAS loci associated with PH, and represent novel regions of potential breeding significance. Notably, these loci exhibit varying effects on PH, contribute significantly to natural variance, and are expressed during seedling to reproductive stages. The haplotype block on chromosome 6A contains five QTN loci associated with reduced height and two loci promoting height. This configuration suggests a substantial impact on natural variation and holds promise for accurate marker-assisted selection. The potentially novel genomic regions harbor putative candidate gene coding for glutamine synthetase, gibberellin 2-oxidase, auxin response factor, ethylene-responsive transcription factor, and nitric oxide synthase; cell cycle-related genes, encoding cyclin, regulator of chromosome condensation (RCC1) protein, katanin p60 ATPase-containing subunit, and expansins; genes implicated in stem mechanical strength and defense mechanisms, as well as gene regulators such as transcription factors and protein kinases. These findings enrich the pool of semi-dwarfing gene resources, providing the potential to further optimize PH, improve lodging resistance, and achieve higher grain yields in bread wheat. Full article

Sporisorium scitamineum is a biotrophic fungus responsible for inducing sugarcane smut disease that results in significant reductions in sugarcane yield. Resistance mechanisms against sugarcane smut can be categorized into structural, biochemical, and physiological resistance. However, structural resistance has been relatively understudied. This study found that sugarcane variety ZZ9 displayed structural resistance compared to variety GT42 when subjected to different inoculation methods for assessing resistance to smut disease. Furthermore, the stomatal aperture and density of smut-susceptible varieties (ROC22 and GT42) were significantly higher than those of smut-resistant varieties (ZZ1, ZZ6, and ZZ9). Notably, S. scitamineum was found to be capable of entering sugarcane through the stomata on buds. According to the RNA sequencing of the buds of GT42 and ZZ9, seven Expansin protein-encoding genes were identified, of which six were significantly upregulated in GT42. The two genes c111037.graph_c0 and c113583.graph_c0, belonging to the α-Expansin and β-Expansin families, respectively, were functionally characterized, revealing their role in increasing the stomatal aperture. Therefore, these two sugarcane Expansin protein-coding genes contribute to the stomatal aperture, implying their potential roles in structural resistance to sugarcane smut. Our findings deepen the understanding of the role of the stomata in structural resistance to sugarcane smut and highlight their potential in sugarcane breeding for disease resistance. Full article

Expansins are cell wall (CW) proteins that mediate the CW loosening and regulate salt tolerance in a positive or negative way. However, the role of Populus trichocarpa expansin A6 (PtEXPA6) in salt tolerance and the relevance to cell wall loosening is still unclear in poplars. PtEXPA6 gene was transferred into the hybrid species, Populus alba × P. tremula var. glandulosa (84K) and Populus tremula × P. alba INRA ‘717-1B4’ (717-1B4). Under salt stress, the stem growth, gas exchange, chlorophyll fluorescence, activity and transcription of antioxidant enzymes, Na⁺ content, and Na⁺ flux of root xylem and petiole vascular bundle were investigated in wild-type and transgenic poplars. The correlation analysis and principal component analysis (PCA) were used to analyze the correlations among the characteristics and principal components. Our results show that the transcription of PtEXPA6 was downregulated upon a prolonged duration of salt stress (48 h) after a transient increase induced by NaCl (100 mM). The PtEXPA6-transgenic poplars of 84K and 717-1B4 showed a greater reduction (42–65%) in stem height and diameter growth after 15 days of NaCl treatment compared with wild-type (WT) poplars (11–41%). The Na⁺ accumulation in roots, stems, and leaves was 14–83% higher in the transgenic lines than in the WT. The Na⁺ buildup in the transgenic poplars affects photosynthesis; the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and the transcription of PODa2, SOD [Cu-Zn], and CAT1. Transient flux kinetics showed that the Na⁺ efflux of root xylem and leaf petiole vascular bundle were 1.9–3.5-fold greater in the PtEXPA6-transgenic poplars than in the WT poplars. PtEXPA6 overexpression increased root contractility and extensibility by 33% and 32%, indicating that PtEXPA6 increased the CW loosening in the transgenic poplars of 84K and 717-1B4. Noteworthily, the PtEXPA6-promoted CW loosening was shown to facilitate Na⁺ efflux of root xylem and petiole vascular bundle in the transgenic poplars. We conclude that the overexpression of PtEXPA6 leads to CW loosening that facilitates the radial translocation of Na⁺ into the root xylem and the subsequent Na⁺ translocation from roots to leaves, resulting in an excessive Na⁺ accumulation and consequently, reducing salt tolerance in transgenic poplars. Therefore, the downregulation of PtEXPA6 in NaCl-treated Populus trichocarpa favors the maintenance of ionic and reactive oxygen species (ROS) homeostasis under long-term salt stress. Full article

The expansin genes are commonly expressed in plant cells, and the encoded proteins influence plant growth and stress resistance by loosening the structure and increasing the flexibility of the cell wall. The objective of this study was to characterize expansin gene promoters in Populus trichocarpa to clarify the regulatory mechanisms underlying gene expression and evolution. Sequence alignments revealed that the similarity among 36 poplar expansin genes was greater for the coding sequences than for the promoter sequences, which suggested these promoter sequences evolved asynchronously. The bases flanking the start codon exhibited a usage bias, with sites +3, +4, and +5 biased toward GC, whereas the other sites were biased toward AT. The flanking sites were significantly correlated with gene expression, especially sites −10 and −17, in which C and G are the bases positively associated with gene expression. A total of 435 regulatory elements (61 types) were identified on the promoters of the poplar expansin genes; Skn-1 was the most common element in 23 promoters. Some expansin genes had more regulatory elements on their promoters (e.g., PtrEXPA4, PtrEXPA3, PtrEXPB3, and PtrEXPB1), whereas some others had less (e.g., PtrEXLA2, PtrEXLB1, and PtrEXPA23). Furthermore, 26 types of elements were involved in expansin gene expression, 25 of which positively affected expression in all analyzed samples. The exception was the endosperm expression-related element Skn-1, which negatively regulated expression in four tissues or treatments. Expression analysis showed that the expansin genes in Populus trichocarpa performed much differently under regular and abiotic stress conditions, which well matched the diversity of their promoter sequences. The results show that expansin genes play an important role in plant growth and development and stress resistance through expression adjustment. Full article