Genome-wide identification of NF-Y genes in kiwifruit genome and the role of AcNF-YC22 in response to heat stress

Nuclear Factor Y (NF-Y) serves as a critical regulator in plant development and stress adaptation. However, comprehensive genome-wide analyses of the NF-Y family remain notably limited in kiwifruit (Actinidia chinensis). In this study, 72 NF-Y genes were identified from kiwifruit genome, including 17 AcNF-YAs, 18 AcNF-YBs and 37 AcNF-YCs. These NF-Y members were further investigated for their chromosomal distribution, phylogenetic evolution, conserved motifs, gene structure, and cis-acting elements. Additionally, the expression profiles of AcNF-Ys in response to heat stress were assessed via transcriptome data and qRT-PCR validation. We also generated transgenic kiwifruit plants that transiently overexpressed and VIGS-mediated silent expression of AcNF-YC22. Under heat stress, the SPAD, relative water content (RWC), and chlorophyll fluorescence parameters (except Y(NO)) in AcNF-YC22-overexpressing plants were significantly higher than those in empty vector controls, whereas electrolyte leakage (EL) and malondialdehyde (MDA) levels were markedly lower. Conversely, AcNF-YC22-silenced plants exhibited the opposite trend. Our findings lay the foundation for future functional studies of the NF-Y gene family in kiwifruit and inform the development of heat-tolerant cultivars through molecular breeding.