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Purpose <p>Ascorbate peroxidases (APXs) are central components of the ascorbate–glutathione cycle that detoxifies hydrogen peroxide (H₂O₂) and maintains cellular redox homeostasis, yet their genomic organization and functional diversification in hexaploid wheat remain incompletely understood.</p> Methods <p>Here, we performed a genome-wide investigation of the APX gene family in <i>Triticum aestivum</i> and integrated in silico and gene expression analyses with physiological and transcriptional responses to drought stress.</p> Results <p>Seventy-two TaAPX proteins were identified, displaying substantial variation in length, charge, predicted stability, and hydrophobicity, but predominantly small-to-medium size, hydrophilic character, and a broad theoretical isoelectric point (pI) range, consistent with operation in diverse cellular micro-environments. Subcellular prediction and GO enrichment revealed a strong bias toward chloroplasts, mitochondria, and cytosol, with frequent dual or multi-targeting, supporting a spatially distributed antioxidant network closely associated with photosynthetic and respiratory membranes. Phylogenetic, gene-structure, and motif analyses clustered TaAPXs into several well-supported subfamilies that are conserved across cereals yet show wheat-specific expansions, indicating ancient diversification followed by lineage-specific amplification and structural specialization. Promoter mining uncovered dense arrays of light-, hormone- and stress-responsive cis-elements, suggesting combinatorial regulation by photosensory and hormonal pathways. Public RNA-seq datasets showed that only a subset of <i>TaAPX</i> genes is strongly induced by drought, drought and heat, and fungal or rust infection, highlighting functional partitioning between housekeeping and stress-responsive isoforms. In a contrasting pair of drought-tolerant and susceptible genotypes, drought markedly enhanced superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities and better preserved ascorbic acid (AsA) and glutathione (GSH) pools in the tolerant line; time-course qRT-PCR demonstrated earlier and stronger induction of several <i>TaAPX</i> genes in the tolerant genotype.</p> Conclusion <p>Together, these results delineate a multi-layered, compartmentalized <i>TaAPX</i> network and identify key drought-responsive isoforms that likely underpin effective redox buffering, providing candidate genes and regulatory modules for improving wheat resilience under water-limited conditions.</p>

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Genome-wide Investigation and Expression Profiling of APX Gene Family in Triticum aestivum L. Provide New Insights Into Redox Homeostasis Maintenance During Drought Stress Conditions

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Fatmah Ahmed Safhi,
  • Ahmad M. Alqudah,
  • Hatem E. Semary,
  • Samar G. Thabet

摘要

Purpose

Ascorbate peroxidases (APXs) are central components of the ascorbate–glutathione cycle that detoxifies hydrogen peroxide (H₂O₂) and maintains cellular redox homeostasis, yet their genomic organization and functional diversification in hexaploid wheat remain incompletely understood.

Methods

Here, we performed a genome-wide investigation of the APX gene family in Triticum aestivum and integrated in silico and gene expression analyses with physiological and transcriptional responses to drought stress.

Results

Seventy-two TaAPX proteins were identified, displaying substantial variation in length, charge, predicted stability, and hydrophobicity, but predominantly small-to-medium size, hydrophilic character, and a broad theoretical isoelectric point (pI) range, consistent with operation in diverse cellular micro-environments. Subcellular prediction and GO enrichment revealed a strong bias toward chloroplasts, mitochondria, and cytosol, with frequent dual or multi-targeting, supporting a spatially distributed antioxidant network closely associated with photosynthetic and respiratory membranes. Phylogenetic, gene-structure, and motif analyses clustered TaAPXs into several well-supported subfamilies that are conserved across cereals yet show wheat-specific expansions, indicating ancient diversification followed by lineage-specific amplification and structural specialization. Promoter mining uncovered dense arrays of light-, hormone- and stress-responsive cis-elements, suggesting combinatorial regulation by photosensory and hormonal pathways. Public RNA-seq datasets showed that only a subset of TaAPX genes is strongly induced by drought, drought and heat, and fungal or rust infection, highlighting functional partitioning between housekeeping and stress-responsive isoforms. In a contrasting pair of drought-tolerant and susceptible genotypes, drought markedly enhanced superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities and better preserved ascorbic acid (AsA) and glutathione (GSH) pools in the tolerant line; time-course qRT-PCR demonstrated earlier and stronger induction of several TaAPX genes in the tolerant genotype.

Conclusion

Together, these results delineate a multi-layered, compartmentalized TaAPX network and identify key drought-responsive isoforms that likely underpin effective redox buffering, providing candidate genes and regulatory modules for improving wheat resilience under water-limited conditions.