Abstract：Kiwifruit is rich in ascorbic acid (AsA), but the AsA content significantly decreases during postharvest ripening. AsA metabolism is regulated by transcription factors. The basic helix-loop-helix (bHLH) gene family has been proven to be involved in various metabolic pathways. To explore the role of the bHLH gene family in AsA metabolism in kiwifruit, this study conducted bioinformatics identification of the kiwifruit (Actinidia chinensis) bHLH gene family. The physicochemical properties, chromosomal localization, conserved motifs, evolutionary relationships, synonymous codon usage frequency, and protein interaction networks of these members were analyzed to determine gene nomenclature and classify the gene family, predicting their interaction relationships. Finally, by analyzing the expression patterns of bHLH transcription factors (TFs) and AsA metabolic genes during postharvest storage, combined with the prediction of cis-acting elements in the promoters of functional genes, the potential links between bHLH TFs and AsA metabolism were inferred. The results showed that the 144 members were distributed across 29 chromosomes, with most members possessing typical bHLH conserved motifs. The cis-acting elements included 7 major categories: Light response, stress response, MYB binding, hormone response, defense and stress response, endosperm and meristem expression and circadian rhythm. According to the phylogenetic tree analysis, 144 bHLH members were divided into 25 subfamilies, of which 7 members having a relative synonymous codon usage frequency greater than 2.0, indicating a strong codon usage preference in the AcbHLH gene family. Protein interaction network analysis revealed interactions among 60 members. qRT-PCR analysis indicated that AcbHLH072, AcbHLH120, AcbHLH134, and AcbHLH067 were significantly correlated with AsA content. Additionally, 8 AsA metabolism-related genes all contained cis-acting elements for bHLH binding, suggesting that AcbHLH072, AcbHLH120, AcbHLH134, and AcbHLH067 might regulate AsA synthesis and degradation by influencing the expression of related genes such as ascorbate peroxidase 2 (AcAPX2), AcAPX8, L-galactose dehydrogenase 1 (AcGalDH1), galacturonic acid uridylyltransferase 2 (AcGalUR2), and AcGalUR3, thereby modulating the AsA metabolic pathway in the fruit. This study provides insights into the mechanisms by which the kiwifruit bHLH gene family participates in ascorbic acid metabolism.
张诗颖, 周靓, 毛甲绪, 王露凡, 沈淑铃, 郑小林, 宦晨. 猕猴桃bHLH基因家族鉴定及其在果实贮藏条件下的表达分析[J]. 农业生物技术学报, 2026, 34(1): 47-65.
ZHANG Shi-Ying, ZHOU Liang, MAO Jia-Xu, WANG Lu-Fan, SHEN Shu-Ling, ZHENG Xiao-Lin, HUAN Chen. Identification of the bHLH Gene Family in Kiwifruit (Actinidia chinensis) and Its Expression Analysis Under Fruit Storage Conditions. 农业生物技术学报, 2026, 34(1): 47-65.
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