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Article

Identification and Expression Profiling of the Cytokinin Synthesis Gene Family IPT in Maize

by
Congcong Chen
1,
Yujie Yan
1,
Dongxiao Li
1,
Weixin Dong
2,
Yuechen Zhang
1,* and
Peijun Tao
1,*
1
College of Agriculture, Hebei Agricultural University, Baoding 071001, China
2
Teaching Support Department, Hebei Open University, Shijiazhuang 050080, China
*
Authors to whom correspondence should be addressed.
Genes 2025, 16(4), 415; https://doi.org/10.3390/genes16040415
Submission received: 4 March 2025 / Revised: 28 March 2025 / Accepted: 28 March 2025 / Published: 31 March 2025
(This article belongs to the Section Plant Genetics and Genomics)
Browse Figures
Versions Notes

Abstract

:
Isopentyltransferase (IPT) is a key rate-limiting enzyme in cytokinin synthesis, playing a crucial role in plant growth, development, and response to adverse conditions. Although the IPT gene family has been studied in various plants, comprehensive identification and functional characterization of IPT genes in maize (Zea mays) remain underexplored. In this study, ten IPT gene family members (ZmIPT1–ZmIPT10) were identified in the maize genome, and their gene structure, physicochemical properties, evolutionary relationships, expression patterns, and stress response characteristics were systematically analyzed. The ZmIPT genes were found to be unevenly distributed across six chromosomes, with most proteins predicted to be basic and localized primarily in chloroplasts. Phylogenetic analysis grouped the ZmIPT family into four subfamilies, showing close evolutionary relationships with rice IPT genes. Conserved motif and gene structure analyses indicated that the family members were structurally conserved, with five collinear gene pairs being identified. Ka/Ks analysis revealed that these gene pairs underwent strong purifying selection during evolution.Cis-element analysis of promoter regions suggested that ZmIPT genes are widely involved in hormone signaling and abiotic stress responses. Tissue-specific expression profiling showed that ZmIPT5, ZmIPT7, and ZmIPT8 were highly expressed in roots, with ZmIPT5 exhibiting consistently high expression under multiple abiotic stresses. qRT-PCR validation confirmed that ZmIPT5 expression peaked at 24 h after stress treatment, indicating its key role in long-term stress adaptation. Protein interaction analysis further revealed potential interactions between ZmIPT5 and cytokinin oxidases (CKX1, CKX5), as well as FPP/GGPP synthase family proteins, suggesting a regulatory role in cytokinin homeostasis and stress adaptation. Overall, this study provides comprehensive insights into the structure and function of the ZmIPT gene family and identifies ZmIPT5 as a promising candidate for improving stress tolerance in maize through molecular breeding.

1. Introduction

Cytokinins are essential for numerous physiological processes in plants, including apical dominance, branching, tillering, leaf senescence, photosynthesis, and stress responses [1,2,3]. Among the key enzymes involved in cytokinin biosynthesis, isopentenyltransferase (IPT) serves as a rate-limiting enzyme, playing a central role in regulating these processes [4,5]. IPT catalyzes the transfer of the isopentenyl group from dimethylallyl diphosphate (DMAPP) to adenosine monophosphate, ultimately leading to cytokinin synthesis, which modulates plant growth and development. IPT can be classified into two main types: ATP/ADP IPT, which modifies adenine in tRNA; and tRNA-IPT, which specifically transfers the isopentenyl group to adenosine monophosphate. This classification highlights the diversity of IPT genes across different plant cells and suggests potential functional differences [6,7,8].
Numerous studies have demonstrated the crucial role of IPT in plant stress responses [9,10,11]. Under heat stress conditions, cytokinin accumulation induced by IPT genes enhances plant thermotolerance by regulating stomatal opening and the expression of photosynthesis-related proteins and transcripts. In transgenic sugarcane, the overexpression of IPT has been shown to increase cold tolerance [12], with similar findings reported in transgenic eggplants [13]. Furthermore, in rice, transgenic IPT plants exhibited significantly higher cytokinin and chlorophyll content under drought stress, thereby improving their tolerance to osmotic stress and drought. This phenomenon has also been documented in transgenic Arabidopsis [14], tobacco [15], and chickpea [16]. Additionally, overexpression of IPT under the control of a stress-inducible promoter (pSARK::IPT) has been linked to delayed drought-induced senescence and enhanced drought resistance in crops such as peanut and cotton [17,18,19,20]. Transgenic plants expressing SAG12-IPT under phosphate starvation conditions demonstrated increased acidic nitrogen and phosphatase activities, indicating the pivotal role of IPT in enhancing plant adaptation to nitrogen- and phosphorus-limited environments [21,22]. IPT genes also significantly contribute to enhancing plant resistance to herbivory by promoting cytokinin synthesis in plant cells. Studies indicate that IPT gene promoters, in conjunction with protease inhibitor II genes, can suppress the growth and development of aphids on peach trees [23]. These findings underscore the essential function of IPT genes in mitigating stress-related damage, thereby improving plant resilience in challenging environments.
Maize (Zea mays) is a crucial crop for global food security, economic stability, and animal feed production. As the global population continues to rise, the demand for food increases, making the improvement of maize yield a critical strategy for ensuring food security [24]. However, climate change and environmental stressors, particularly extreme temperatures, drought, and water scarcity, significantly impact maize growth and development, severely limiting its yield potential. Recent research has underscored the essential role of cytokinins in maize’s response to environmental stresses [25,26]. Cytokinins not only enhance maize’s adaptability to drought and salinity stress by regulating root growth, leaf development, and water use efficiency, but they also play a significant role in modulating antioxidant enzyme systems and improving stress resistance [27,28,29]. Therefore, a comprehensive understanding of the functions of cytokinins in maize’s stress resistance mechanisms is of substantial theoretical and practical significance for enhancing maize resilience and advancing global food production.
To date, several plant species have been identified to contain IPT genes, including Arabidopsis [30], rice [31], apple [32], tomato [33], and soybean [34]. However, a comprehensive examination of the IPT gene family in maize remains lacking. In this study, we employed bioinformatics techniques to identify the members of the maize IPT family and conducted a detailed analysis of their gene structures, evolutionary relationships, conserved motifs, syntenic relationships, cis-acting elements, and expression patterns. This research provides a solid theoretical foundation for further investigations into the functional roles of IPT family members in maize.

2. Materials and Methods

2.1. Genome-Wide Identification and Physicochemical Properties Analysis of the Maize IPT Gene Family Members

First, we retrieved the IPT protein domain file in the Hidden Markov model format from the Pfam database (http://pfam.xfam.org/ accessed on 1 January 2020). We then used HMMER 3.0 to generate the maize IPT protein sequence file. Next, we visited the NCBI database (https://www.ncbi.nlm.nih.gov/, accessed on 1 September 2024) to further identify the protein domain linked to the candidate gene. After this process, the amino acid sequence devoid of the IPT domain was ultimately acquired. The amino acid length, molecular weight, isoelectric point, and other relevant indicators of the candidate IPT family members were analyzed using ProtParam and ProtScale in ExPASy (https://web.expasy.org/protparam/, accessed on 1 September 2024). Subcellular localization was assessed through the WoLF PSORT Prediction tool (https://wolfpsort.hgc.jp/, accessed 1 September 2024), while the gene’s localization data was visualized with TBtools-II software to identify the chromosome’s length and position that corresponds to the maize IPT gene information. We downloaded the IPT protein sequences of Arabidopsis, rice, and soybean from the EnsemblPlants database (https://plants.ensembl.org/index.html, accessed on 1 September 2024). We utilized MEGA7 for multi-sequence alignment and employed iTOL for the beautification of the phylogenetic tree. Subsequently, we extracted the sequence 2000 bp upstream of the transcription start site of the candidate IPT family gene in maize using TBtools software. The Plant CARE tool (http://bioinformatics.psb.ugent.be/webtools/plantcare/html/, accessed on 1 September 2024) will be utilized to anticipate the cis-acting elements within the promoter region for a member of the maize IPT gene family using this 2000 bp sequence. Additionally, we performed collinear visual analysis of the IPT gene within the maize genome using TBtools software. Finally, we utilized PPRD (http://ipf.sustech.edu.cn/pub/plantrna, accessed 1 September 2024) to investigate and gather data on the expression levels of ZmIPTs within diverse maize tissues and in response to different abiotic stress conditions.

2.2. Plant Material and Stress Treatments

The study took place in June 2024 at Hebei Agricultural University’s Agricultural College, located in Baoding, Hebei (38.82 °N, 115.45 °E). The maize variety Zhengdan 958, provided by Pioneer Seed Industry, was used as the experimental material. The seedling matrix consisted of a mixture of vermiculite and nutrient soil in a volume ratio of 3:1, and the seedlings were cultivated in an incubator set to 25 °C, with a relative humidity of 65% and a photoperiod of 16 h light and 8 h dark. When the maize seedlings reached the two-leaf and one-center stage, those exhibiting consistent growth potential were selected for follow-up experiments.
Tissue expression analysis was conducted on the root, shoot, and leaf parts of maize seedlings to assess gene expression.
Five treatment conditions were established for the abiotic stress experiments: (1) CK, which involved maize seedlings under standard management practices; (2) Heat stress, where the incubator temperature was maintained at 42 °C during the day and 25 °C at night; (3) Cold stress, with the temperature in the incubator adjusted to 4 °C during the day and 10 °C at night; (4) Drought stress, achieved by employing a 20% PEG-6000 solution; (5) Salt stress, where the roots were irrigated with a 200 mM NaCl solution. For each treatment and control group, three biological replicates were performed. Samples were taken at 0, 1, 6, and 12 h, with blade samples rapidly frozen in liquid nitrogen and preserved in a −80 °C freezer for later analysis.

2.3. Total RNA Extraction, cDNA Reverse Transcription, and Quantitative Real-Time PCR Analysis

RNA extraction was conducted using a kit from Beijing Huayueyang Co., Ltd. (Beijing, China). Reverse transcription and real-time fluorescence quantitative PCR analyses were performed with this RNA rapid extraction kit. Primers were designed with actin as the internal control gene using Primer 6.0 (Table S1). The cycling procedure included an initial denaturation step at 95 °C lasting 30 s, succeeded by 40 cycles of three-step amplification: 95°C for 5 s, 57 °C for 10 s, and 72 °C for 20 s, followed by a melt curve analysis. The gene’s relative expression was determined using the 2−ΔΔCt method, and statistical variations were assessed with a significance threshold of p < 0.05.

2.4. Statistics and Analysis

The data were generated with Microsoft Excel 2021, assessed for significance through the DPS 7.05 software, and visualized with Origin 2021.

3. Result

3.1. Identification and Physicochemical Property Analysis of the Maize IPT Gene Family

In the maize genome, the present researchers identified a total of ten members of the IPT family, labeled as ZmIPT1 to ZmIPT10. The physical and chemical properties of the maize IPT proteins were analyzed, with results presented in Table 1. The average length of the maize IPT family amino acids was 368.1 amino acids (aa), and the average relative molecular mass was 39,778.19 Da. Among these, ZmIPT5 exhibited the longest amino acid sequence and the highest relative molecular mass, while ZmIPT4 displayed the shortest amino acid sequence and the lowest relative molecular mass. ZmIPT1 and ZmIPT2 are characterized by a positive charge, whereas the remaining proteins possess a negative charge. The average isoelectric point (pI) value is 8.13; with the exception of ZmIPT2 and ZmIPT4, all other proteins have a pI greater than 7, suggesting a potential role in alkaline subcellular environments. TargetP-based subcellular localization predictions showed that most members of the IPT gene family (IPT1, IPT3, and IPT5-IPT10) are localized in the chloroplast, while only a few members (IPT2 and IPT4) are localized in the cytoplasm, suggesting a considerable degree of functional divergence within the family at the subcellular level. Combined with the SignalP analysis, which indicated that all members have D-scores far below the threshold of 0.45, it can be inferred that these proteins lack typical N-terminal signal peptides and are unlikely to be secreted via the classical secretory pathway(see Table S2). Instead, they are likely to function within specific intracellular compartments-particularly in the chloroplast-where they may participate in cytokinin biosynthesis or regulation. In addition, chromosomal localization analysis revealed that the 10 ZmIPT genes are distributed across six different chromosomes, showing a relatively dispersed pattern within the maize genome (see Figure 1).

3.2. Phylogenetic Analysis of the ZmIPT Gene Family

To further elucidate the evolutionary relationships within the maize IPT gene family, we selected 42 IPT protein sequences from maize (10), Arabidopsis (9), rice (9), and soybean (15) to construct a phylogenetic tree. The findings suggest that the 42 IPT proteins can be divided into four distinct subfamilies (G1–G4). Interestingly, the IPT genes found in maize are spread throughout all subfamilies, indicating substantial variations in the IPT protein family across different species. Additionally, the IPT families of maize and rice exhibit a closer homology relationship (Figure 2).

3.3. Analysis of Conserved Motifs in the ZmIPT Gene Family

We identified eight conserved motifs within the ZmIPT proteins. Notably, Motif1 and Motif3 are functional domains shared among all ten IPT protein sequences, suggesting that these two motifs may play a crucial role in the functions of family members. Additionally, ZmIPT3 contains only four motifs, which is significantly fewer than those found in other genes, while ZmIPT1 and ZmIPT2 each contain the maximum of ten motifs. This disparity may reflect the structural and functional diversity among the different genes. Through clustering analysis, we observed that members with similar structures were grouped into the same subfamily (Figure 3A,B). All members of the ZmIPT gene family contain introns; however, only ZmIPT5 possesses two UTR non-coding regions. This suggests that the genetic architecture of the maize ZmIPT gene family is comparatively straightforward, and genes belonging to the same subfamily might display analogous functions (Figure 3C).

3.4. Synteny Analysis of the ZmIPT Gene Family

TBtools was employed to perform a collinear analysis of the maize IPT gene family, with the findings presented in Figure 4. This analysis revealed a total of five gene pairs within the family: ZmIPT1 with ZmIPT3, ZmIPT1 with ZmIPT7, ZmIPT6 paired with ZmIPT9, ZmIPT6 associated with ZmIPT10, and ZmIPT9 alongside ZmIPT10. Additionally, the genes exhibiting collinear relationships are categorized within the same subfamily, indicating their similar structural and functional characteristics. Further examination revealed that these collinear genes are part of the same subfamily, suggesting that they may have undergone gene duplication events during evolution. Consequently, these genes we found to hold significant importance for the functionality of the maize IPT family. Further analysis based on Ka/Ks ratios revealed that all five gene pairs have Ka/Ks values significantly lower than 1 (ranging from 0.05 to 0.20; detailed values provided in Supplementary Tables S3 and S4), indicating strong purifying selection during their evolutionary history. These results imply that these genes have conserved functions and likely play essential roles in the maize IPT gene family.

3.5. Analysis of Cis-Acting Elements in the Promoters of the ZmIPT Gene Family

In this research, we performed an analysis of the cis-acting elements within the promoter region situated 2000 bp upstream of the maize IPT gene, as illustrated in Figure 5. The cis-acting elements identified consisted of elements responsive to light, elements associated with stress responses, those linked to plant growth and development, as well as elements related to plant hormone responses. Among the IPT genes analyzed, ZmIPT2 exhibited the fewest cis-acting elements, while ZmIPT7 contained the most. Notably, all IPT genes featured the abscisic acid response element ABRE, suggesting a significant role in regulating abscisic acid levels. With the exception of ZmIPT8, most IPT genes also possessed the auxin response element TGA, indicating their involvement in auxin regulation. Furthermore, all genes except for ZmIPT2 contained anaerobic induction-related elements (ARE) and light-responsive elements (G-Box), demonstrating that the majority of these genes respond to environmental signals and light induction.

3.6. Expression Analysis of ZmIPT Genes in Different Tissues

We analyzed the expression patterns of the maize IPT gene family across various tissues. The results indicate that the ZmIPT5, ZmIPT7, and ZmIPT8 genes are highly expressed in the roots, particularly ZmIPT5, suggesting a significant role for these genes in maize root growth and hormone synthesis. In contrast, the expression levels of the ZmIPT2 and ZmIPT3 genes in stems and leaves were nearly undetectable. Additionally, the ZmIPT4, ZmIPT6, and ZmIPT10 genes generally exhibited low expression levels. Overall, the observed differences in IPT gene expression across different tissues reflected the distinct functions of each gene in maize growth and development (Figure 6).

3.7. Expression Analysis of IPT Gene in Maize Under Abiotic Stress

To investigate the response of IPT genes to abiotic stress in greater detail, we utilized a database to analyze the expression profiles associated with these genes. Our findings revealed distinct variations in the expression patterns of the ZmIPT genes. Notably, during exposure to both high and low temperature stress, the expression levels of ZmIPT5 and ZmIPT8 showed significant increases. In response to UV and drought stress, ZmIPT5, ZmIPT7, and ZmIPT8 exhibited the highest expression levels. For nutritional stress, as well as saline-alkali and shade stress, ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 displayed relatively high expression. Furthermore, ZmIPT1 showed increased expression under flooding conditions. Importantly, ZmIPT5 exhibited elevated expression levels across various abiotic stress conditions, highlighting its potential significance in mediating plant responses to these stressors (Figure 7).
To explore how IPT genes responded to abiotic stresses such as heat, cold, drought, and salt stress, we analyzed the spatiotemporal expression variations of these genes under different stress conditions using qRT-PCR. The results indicate that ZmIPT2, ZmIPT7, and ZmIPT8 are rapidly upregulated during the early stages of stress (at 1 h or 6 h), suggesting that these genes may facilitate a swift plant response and adaptation to environmental changes by regulating cytokinin synthesis and signaling. In contrast, ZmIPT5 exhibited relatively continuous high expression across all stress conditions, peaking at 24 h, which suggests its significant role in long-term adaptive responses. Specifically, the early response of ZmIPT2 to both high and low temperatures, the sustained expression of ZmIPT5 under various stresses, the initial activation of ZmIPT7 under low and saline conditions, and the mid-term regulation of ZmIPT8 during drought and salinity collectively indicate that these genes serve distinct biological functions in the plant’s responses to abiotic stress (Figure 8).

3.8. Prediction of Interacting Proteins of IPT5 in Maize

In our investigation of the interaction proteins of ZmIPT5, we identified that it is primarily associated with CKX1, CKX5, and proteins from the FPP/GGPP synthase family. CKX1 and CKX5 belong to the cytokinin oxidase family and are primarily responsible for the degradation of cytokinins (CKs). This association suggests that ZmIPT5 may be involved in regulating cytokinin metabolism, playing a crucial role in maintaining the balance between cytokinin synthesis and degradation, which, in turn, influences plant growth and development-particularly in roots and other tissues where precise regulation of cytokinin levels is essential. Furthermore, the FPP/GGPP synthase family is primarily involved in the synthesis of farnesyl and geranylgeranyl pyrophosphates, which serve as precursors for plant growth hormones, secondary metabolites, and signaling molecules. The interaction with these enzymes indicates that ZmIPT5 may also have a regulatory function in hormone synthesis, contributing to plant developmental processes and responses to environmental stress (Figure 9).

4. Discussion

The IPT gene family has been recognized across various species [32,35,36,37], with many investigations revealing that IPT genes are essential for plant growth, development, and responses to environmental stresses [35,36]. However, the specific functions of IPT genes in maize remain unknown. This study systematically analyzed 10 members of the IPT family. Analysis of their physical and chemical properties reveals significant differences in the lengths of amino acid sequences and relative molecular masses among maize IPT family members, which may contribute to the functional diversity observed. Research indicates that most IPT genes are localized to the plastids, while a smaller number are found in the mitochondria [9]. In Arabidopsis, AtIPT1, 3, 5, and 8 are localized to plastids, AtIPT4 is found in the cytoplasm, and AtIPT7 is localized to the mitochondria [37]. In maize, eight IPT genes are located in the chloroplast, and two are situated in the cytoplasm, suggesting that maize IPT proteins function in both the chloroplast and cytoplasm. Most IPT genes exhibit isoelectric points greater than 7, indicating that they may function effectively in alkaline environments, which aligns with their distribution in the chloroplast and cytoplasm. As chloroplasts are crucial sites for plant hormone synthesis, this suggests that IPT genes play a fundamental role in regulating plant growth, photosynthesis, and stress responses.
Through the construction of phylogenetic trees, we observed that maize IPT genes were distributed across various subfamilies, exhibiting significant homology. This indicates that IPT genes among different species share common evolutionary foundations in terms of structure [38]. Moreover, the proximity of maize to the rice IPT gene family may reflect their shared history of gene duplication and functional differentiation during evolution [39]. We identified eight conserved motifs, with Motif1 and Motif3 being present in all ten IPT protein sequences. The variation in the number of motifs among different genes—such as ZmIPT1 and ZmIPT2, which contain the most motifs (ten), while ZmIPT3 has only four—suggests functional differences among these genes, potentially correlating with their roles in plant growth and environmental responses. The variations in the characteristics of stimuli were also found to be interconnected. The primary factor behind the expansion of gene families in plants is the replication of gene fragments, which results in the development of unique functions following gene duplication [40]. Collinearity analysis revealed five pairs of collinear gene relationships, all within the same subfamily, indicating that these genes may have preserved similar functional properties throughout evolution [41]. Studies have demonstrated that IPT genes play a crucial role in regulating plant responses to adverse stresses. Identifying and characterizing cis-regulatory sequences is essential for processes like plant development and responses to environmental changes [42].
Research indicates that auxin can function as a signaling molecule, inducing the expression of stress-resistant genes when plants experience abiotic stress. For instance, during the reproductive phase of soybean, GmIPT8 and GmIPT10 are upregulated in response to drought stress [43]. The cis-acting element analysis conducted in this study has uncovered the potential roles of IPT genes in phytohormone signaling, stress responses, and growth and development processes. Importantly, the prevalent occurrence of ABRE and TGA elements suggests that the maize IPT gene family may play a role in the plant’s response to challenging conditions. Gene expression is modulated by transcription factors interacting with cis-acting elements found in promoter regions of genes [44]. To further analyze the expression patterns of ZmIPT genes, this study utilized public RNA-seq database data to conduct a preliminary analysis of 10 ZmIPT genes. The findings indicate that AtIPT3, AtIPT5, and AtIPT7 genes in Arabidopsis exhibit stable and moderate expression across various tissues [36]. In rice, OsIPT1 and OsIPT2 are expressed at higher levels in roots, stem tips, and flowers. Our research indicated that the expression of ZmIPT genes in various tissues showed no considerable variations, with ZmIPT5 being consistently expressed across all tissue types. This suggests that ZmIPT5 could be involved at every stage of maize development.
In agricultural production, common abiotic stresses include extreme temperatures, salinity, drought, and flooding. Previous research has shown that salt stress can result in reduced cytokinin levels in Arabidopsis, thereby improving the plant’s ability to withstand salt stress [14]. We analyzed the expression of 10 ZmIPT genes in various tissues under conditions of extreme temperature, drought, and salt stress. Notably, ZmIPT5 exhibited high expression under diverse abiotic stress conditions, suggesting its potential role in regulating plant responses to these stresses and highlighting its possible function as a key regulator in enhancing maize’s tolerance to adverse conditions.

5. Conclusions

This study systematically identified 10 IPT family members (ZmIPT1–ZmIPT10) in the maize genome and comprehensively analyzed their gene structures, physicochemical properties, evolutionary relationships, expression patterns, and responses to abiotic stress. The findings not only clarified the structural evolution and regulatory characteristics of the ZmIPT gene family but also highlighted the functional roles of key genes—particularly ZmIPT5, which exhibited sustained high expression and broad involvement under stress conditions. These results significantly advance our understanding of cytokinin biosynthesis regulation in plants and provide valuable insights into the synergistic roles of phytohormones in abiotic stress tolerance. Moreover, the data and conclusions from this study offer important theoretical foundations and genetic resources for the molecular breeding of stress-tolerant maize varieties, contributing to the improvement of crop stability and resource-use efficiency under climate change conditions.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/genes16040415/s1, Table S1: Primer Design; Table S2: SignalP analysis and subcellular localization prediction of the IPT gene family; Table S3: Sequence of the IPT gene family; Table S4: KaKsanalysis of gene pairs.

Author Contributions

Conceptualization: C.C. and Y.Y.; Writing—original draft preparation: Y.Y.; Writing—review and editing: D.L. and W.D.; Supervision and project management: P.T. and Y.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Key Research and Development Program of China (Grant No. 2023YFD2301505).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The data are available upon request from the corresponding author.

Conflicts of Interest

The authors declare that they have no conflict of interest.

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Figure 1. Distribution of the ZmIPT Gene Family on Chromosomes.
Figure 1. Distribution of the ZmIPT Gene Family on Chromosomes.
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Figure 2. Phylogenetic Tree of the IPT Gene Family. The IPT members of Arabidopsis thaliana (At), rice (Os) and maize (Zm) are identified by red circles, blue circles, and yellow squares, respectively, and the numbers on the branches of the phylogenetic tree represent the self development values.
Figure 2. Phylogenetic Tree of the IPT Gene Family. The IPT members of Arabidopsis thaliana (At), rice (Os) and maize (Zm) are identified by red circles, blue circles, and yellow squares, respectively, and the numbers on the branches of the phylogenetic tree represent the self development values.
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Figure 3. Evolutionary tree of the ZmIPT gene family. (A), Conserved Motifs (B), and Gene structure analysis (C).
Figure 3. Evolutionary tree of the ZmIPT gene family. (A), Conserved Motifs (B), and Gene structure analysis (C).
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Figure 4. Synteny analysis of ZmIPT gene family.
Figure 4. Synteny analysis of ZmIPT gene family.
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Figure 5. Distribution of Cis-Acting Elements in the ZmIPT gene family.
Figure 5. Distribution of Cis-Acting Elements in the ZmIPT gene family.
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Figure 6. Tissue-Specific Expression Analysis of ZmIPT Gene family. The different letters in the figure represent significant differences with a p-value less than 0.05.
Figure 6. Tissue-Specific Expression Analysis of ZmIPT Gene family. The different letters in the figure represent significant differences with a p-value less than 0.05.
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Figure 7. Abiotic stress expression analysis of ZmIPT gene family. (a) heat stress. (b) cold stress. (c) ozone stress. (d) drought stress. (e) water stress. (f) innutrition stress. (g) salt stress. (h) shade stress.
Figure 7. Abiotic stress expression analysis of ZmIPT gene family. (a) heat stress. (b) cold stress. (c) ozone stress. (d) drought stress. (e) water stress. (f) innutrition stress. (g) salt stress. (h) shade stress.
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Figure 8. Expression analysis of ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 under heat stress, cold stress, drought stress and salt stress at 0, 1, 6 and 12 h. (a–d) show the expression levels of ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 under heat stress, while (e–h) depict the expression levels of these genes under cold stress. (i–l) present the expression levels of ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 under drought stress, and (m–p) illustrate the expression levels of these genes under salinity stress.
Figure 8. Expression analysis of ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 under heat stress, cold stress, drought stress and salt stress at 0, 1, 6 and 12 h. (a–d) show the expression levels of ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 under heat stress, while (e–h) depict the expression levels of these genes under cold stress. (i–l) present the expression levels of ZmIPT2, ZmIPT5, ZmIPT7, and ZmIPT8 under drought stress, and (m–p) illustrate the expression levels of these genes under salinity stress.
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Figure 9. The interacting protein prediction of ZmIPT5. The colored nodes in the figure represent query proteins and the first shell of interactors, while the white nodes represent the second shell of interactors. Filled nodes indicate that a 3D structure is known or predicted. The light blue edges represent interactions from curated databases, purple-red edges represent experimentally determined interactions, green edges represent gene neighborhood, red edges represent gene fusions, blue edges represent gene co-occurrence, yellow edges represent text mining, black edges represent co-expression, and purple edges represent protein homology.
Figure 9. The interacting protein prediction of ZmIPT5. The colored nodes in the figure represent query proteins and the first shell of interactors, while the white nodes represent the second shell of interactors. Filled nodes indicate that a 3D structure is known or predicted. The light blue edges represent interactions from curated databases, purple-red edges represent experimentally determined interactions, green edges represent gene neighborhood, red edges represent gene fusions, blue edges represent gene co-occurrence, yellow edges represent text mining, black edges represent co-expression, and purple edges represent protein homology.
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Table 1. Information and Physicochemical Properties of the Maize IPT Gene Family Members.
Table 1. Information and Physicochemical Properties of the Maize IPT Gene Family Members.
Gene NameGene IDChromosomal LocationProtein LengthMW (kDa)pISubcellular Localization Prediction
ZmIPT1Zm00001eb062030Chr1:298566258..298567661 (+)33836,488.49.04chloroplast
ZmIPT2Zm00001eb084710Chr2:64584655..64585825 (+)32234,485.84.88cytoplasm
ZmIPT3Zm00001eb095250Chr2:165161688..165163248 (−)34737,2388.22chloroplast
ZmIPT4Zm00001eb131660Chr3:67863267..67864159 (−)29431,9535.92cytoplasm
ZmIPT5Zm00001eb139980Chr3:147368450..147371548 (−)47052,240.57.34chloroplast
ZmIPT6Zm00001eb156350Chr3:212809994..147371548 (−)36939,117.19.56chloroplast
ZmIPT7Zm00001eb212350Chr5:3603911..3605426 (−)33736,571.79.97chloroplast
ZmIPT8Zm00001eb271810Chr6:91352085..91357228 (−)45350,884.27.22chloroplast
ZmIPT9Zm00001eb294970Chr6:174266460..174268235 (−)38840,656.88.98chloroplast
ZmIPT10Zm00001eb360550Chr8:155530469..155532662 (−)36338,146.410.17chloroplast
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Chen, C.; Yan, Y.; Li, D.; Dong, W.; Zhang, Y.; Tao, P. Identification and Expression Profiling of the Cytokinin Synthesis Gene Family IPT in Maize. Genes 2025, 16, 415. https://doi.org/10.3390/genes16040415

AMA Style

Chen C, Yan Y, Li D, Dong W, Zhang Y, Tao P. Identification and Expression Profiling of the Cytokinin Synthesis Gene Family IPT in Maize. Genes. 2025; 16(4):415. https://doi.org/10.3390/genes16040415

Chicago/Turabian Style

Chen, Congcong, Yujie Yan, Dongxiao Li, Weixin Dong, Yuechen Zhang, and Peijun Tao. 2025. "Identification and Expression Profiling of the Cytokinin Synthesis Gene Family IPT in Maize" Genes 16, no. 4: 415. https://doi.org/10.3390/genes16040415

APA Style

Chen, C., Yan, Y., Li, D., Dong, W., Zhang, Y., & Tao, P. (2025). Identification and Expression Profiling of the Cytokinin Synthesis Gene Family IPT in Maize. Genes, 16(4), 415. https://doi.org/10.3390/genes16040415

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