Plant stress adaptation and development are regulated by abscisic acid (ABA), whose biosynthesis is catalyzed by the 9-cis-epoxycarotenoid dioxygenase (NCED) enzymes. In wheat ( Triticum aestivum L.), a comprehensive pan-phylogenomic and functional characterization of the NCED gene family remains underexplored despite its role in ABA synthesis and its likely resilience to abiotic stresses. This study conducts pan-genomic identification, genomic diversity, and functional analyses of the NCED gene family across 14 wild and modern wheat species. A total of 443 non-redundant NCED genes were identified and classified into distinct NCED and carotenoid cleavage dioxygenase (CCD) clades. Gene structure and motifs demonstrated high conservation of the functional RPE65 domain, with promoter-region cis-acting elements enriched for motifs responsive to abiotic stresses and hormone signaling. Expression analysis and RT-qPCR validation identified core stress-responsive genes, including TaCSNCED18 , TaCSNCED26 , and TaCSNCED27 , significantly upregulated under drought and heat stress. TaCSNCED33 is enriched in transfer tissues (aleurone layer and seed coat) and in other storage tissues, as revealed by a spatial transcriptome analysis. Moreover, a haplotype analysis reveals its significant association with thousand-kernel weight (TKW), an agronomic trait related to yield. This work presents a comprehensive genomic atlas of the wheat NCED gene family, detailing its evolutionary history, regulatory architecture, and functional diversification. These findings provide a valuable genetic resource for breeding climate-resilient wheat varieties by optimizing the ABA pathway. • Pan-genome-wide identification of NCED genes, expanding with ploidy • Key genes validated as core responders to abiotic stress • TaCSNCED33 localizes to grain tissues mapped via spatial transcriptomics • TaCSNCED33 haplotype associates with thousand‑kernel weight in wheat
Javed et al. (2026) studied this question.