HD-ZIP proteins (homeodomain–leucine zipper proteins) are a large family of plant-specific transcription factors that play crucial roles in regulating various physiological and developmental processes, including growth, differentiation, response to environmental stress, and reproductive development. Seed size is the main limiting factor affecting the yield of maize (Zea mays). However, the genome-wide identification and characterization of this family in maize and its biological functions in seed size have not been reported. Here, 61 ZmHD-ZIP genes were identified in the genome. Phylogenetic analysis of these ZmHD-ZIP genes revealed that they are clustered into four subfamilies: HD-ZIP I, HD-ZIP II, HD-ZIP III, and HD-ZIP IV. Domain analysis revealed that the distribution of these domains aligns perfectly with the subfamily classification criteria, with members of the same subfamily sharing similar domains. Cis-acting element analysis showed that the ZmHD-ZIP family genes are involved in the regulation of plant reproductive development. In addition, ZmHD-ZIP23-overexpressing Arabidopsis and maize had larger seed with increased grain length and heavier grain weight owing to bigger embryo and endosperm area. These findings could serve as a basis for future studies on the roles of ZmHD-ZIP genes in improving maize yield.

In plants, the diverse enzymes known as BAHD acyltransferases use acyl coenzyme A (acyl-CoA) as their substrate and fulfill crucial biological functions. In this study, 94 NtBAHD genes were identified in the tobacco ( Nicotiana tabacum ) genome. These genes displayed considerable diversity in their physicochemical properties, phylogenetic relationships, gene structures, and conserved motifs. Chlorogenic acid (CGA), which is the predominant polyphenol found in tobacco leaves, is mainly synthesised via the hydroxycinnamoyl-CoA:quinate hydroxycinnamoyl transferase (HQT) pathway. Four HQT genes ( NtHQT1 – NtHQT4 ) were identified in the BAHD gene family of N. tabacum . Of these, NtHQT1 and NtHQT2 were highly expressed in leaves, while NtHQT3 and NtHQT4 were root-specific. Following heterologous expression in vitro , three of the four HQT proteins (NtHQT2, NtHQT3, and NtHQT4) were obtained in soluble form; however, only NtHQT2 and NtHQT3 exhibited enzymatic activity. Downregulation of NtHQT1 , NtHQT2 , NtHQT3 , and NtHQT4 significantly reduced both total polyphenol and chlorogenic acid (CGA) content, whereas the levels of rutin, scopoletin, and lignin remained unchanged. Furthermore, the expression of NtHQT genes was differentially induced under abiotic and biotic stresses, including drought, cold, and Phytophthora nicotianae infection. In contrast, their responses to various phytohormones exhibited distinct expression profiles. These results suggest that whereas in vitro assays identified NtHQT2 and NtHQT3 as the catalytically active isoforms, all four NtHQT genes contribute to chlorogenic acid (CGA) biosynthesis and environmental adaptation. Trial registration This study does not involve clinical trials or human participants and, as such, does not require clinical trial registration.

The nuclear factor Y (NF-Y) transcription factor family plays crucial roles in plant growth, development, and stress responses. However, studies on the NF-Y family in maize remain relatively limited. In this study, we identified 53 NF-Ys in the maize genome, which were classified into ZmNF-YA, ZmNF-YB, and ZmNF-YC subfamilies. These genes exhibited diverse physicochemical properties and were unevenly distributed across the 10 chromosomes. Synteny analysis revealed 48 collinear gene pairs between maize and rice, indicating close evolutionary relationships. Gene structure and conserved motif analyses showed both conservation and divergence within the family. Promoter analysis identified abundant cis-acting elements related to hormone response, abiotic stress, light response, and growth regulation. Expression profiling under drought stress revealed that ZmNF-Ys respond differentially, with some showing strong induction. Functional characterization demonstrated that ZmNF-YA7 positively regulates drought tolerance in maize. Overexpression of ZmNF-YA7 enhanced drought tolerance through multiple mechanisms: reducing oxidative damage by increasing antioxidant enzyme activities, accumulating osmoprotectants, and modulating xylem vessel anatomy (larger diameter and lower density under drought). These findings provide comprehensive insights into the ZmNF-Y gene family and highlight ZmNF-YA7 as a promising candidate for improving drought tolerance in maize breeding programs.