Summary: Changes in skin colour, as a visual cue for fruit ripeness, are important physiological markers in many crops including tomato, banana and grape. In kiwifruit, the skin remains brown during ripening, but de‐greening of the pericarp occurs to reveal accumulated carotenoids and anthocyanins in gold‐ and red‐fleshed cultivars. In this study, analysis of the inner and outer pericarp of Actinidia chinensis ‘Hongyang’ revealed faster chlorophyll degradation in the inner pericarp, compared with the outer pericarp. Based on transcriptome analysis, two chlorophyll degradation‐related genes encoding Mg‐dechelatases (AcSGR1 and AcSGR2) were more abundantly expressed in the inner pericarp, and this correlated with higher Mg‐dechelatase enzyme activity in the inner pericarp than in the outer pericarp. Weighted gene co‐expression network analysis identified potential regulators of AcSGR1/2. A differentially expressed NAM/ATAF/CUC transcription factor AcNAC2 was identified, which could directly interact with AcSGR1 and AcSGR2 promoters and strongly activate their expression. A closely related NAC, AcNAC3, also enhanced AcSGR1/2 expression, but was less abundantly expressed. Transient expression in tobacco confirmed that AcNAC2 and AcNAC3 promote chlorophyll degradation, and stable overexpression in kiwifruit verified that AcNAC2 acts via up‐regulation of AcSGR1/2 gene expression. CRISPR‐mediated knockouts of AcNAC2/3 in kiwifruit dramatically reduced expression levels of AcSGR1/2 genes in fruit, leading to significantly delayed chlorophyll degradation and de‐greening. Together, these results suggest that differential chlorophyll degradation drives the differences observed in chlorophyll content between the inner and outer pericarp of kiwifruit, which is principally modulated by the transcription factor AcNAC2.

The kiwifruit (genus Actinidia) exhibits extensive polyploidy, with natural populations ranging from diploid to tetraploid, hexaploid, and even higher ploidy levels. Actinidia deliciosa (green kiwifruit) is typically hexaploid (2n = 6x = 174), whereas its close relative A. chinensis (golden kiwifruit) is primarily diploid (2n = 2x = 58) or tetraploid. This ploidy diversity reflects a reticulate evolutionary history, likely shaped by hybridization and genome duplication involving multiple ancestral lineages. Determining the origin and inheritance of hexaploid A. deliciosa—the dominant kiwifruit species in global cultivation—is critical for understanding the role of polyploidization in the evolution of this species and for the development of breeding strategies.

Kiwifruit (Actinidia deliciosa) contributes >4 million tons to global fruit production annually and ranks among the highest dietary sources of vitamin C and bioactive polyphenols. Its quality is mainly influenced by the coordinated regulation of essential metabolites during fruit ripening. Although several important metabolites associated with fruit color, flavor, and nutrition have been elucidated, the dynamic changes and regulatory networks of ripening-associated metabolites remain largely unexplored. In this study, comprehensive metabolic dynamics of developing fruit of Actinidia deliciosa cv. Xuxiang (‘XX’) were investigated through a widely targeted metabolomic analysis. Three metabolites associated with hormone metabolism showed that differentially accumulated 12-oxo-phytodienoic acid (12-OPDA) and jasmonic acid (JA) were downregulated, while abscisic acid (ABA) was upregulated in XX9 vs. XX21, with a Log₂|fold change| of −1.96, −3.09, and 1.76, respectively. Two hub genes (AdOPR3 and AdCYP707A4) were then screened based on integrative analyses of metabolome and transcriptome data, and showed significantly decreased expression during ‘XX’ fruit ripening, which might be responsible for the reduced content of JA and enhanced level of ABA, respectively. Furthermore, co-expression networks of AdOPR3 and AdCYP707A4 were constructed by WGCNA and the potential transcriptional regulators of these two hub genes were predicted based on a correlation threshold over 0.9. Taken together, these results revealed the opposing accumulation patterns of JA and ABA might contribute to physiological ripening in kiwifruit, via the TF-mediated transcriptional regulation of AdOPR3 and AdCYP707A4. These findings provide insights for hormonal control of fruit ripening.

Anthocyanins, as natural pigments belonging to the flavonoid group, play a crucial role in plant reproduction, stress resistance and human fitness. Kiwifruit, which is rich in anthocyanins, demonstrates significant potential for promoting health benefits. Although light is widely recognized as an inducer of anthocyanin accumulation, we observed that kiwifruit accumulates more anthocyanin after bagging treatment. This unexpected finding suggests that anthocyanin biosynthesis in kiwifruit may also be regulated by other environmental or physiological factors influenced by bagging, such as humidity, temperature, or gas exchange. This implies that bagging may trigger specific regulatory pathways that promote anthocyanin accumulation through multiple environmental cues beyond light. Therefore, RNA-seq was performed to find the potential pathway. A total of 260 differentially expressed genes were found, including 8 transcription factors and 1 anthocyanin biosynthesis gene F3GT1 (glucosyltransferase). Dual-luciferase reporter assays revealed that bHLH transcription factors could activate the promoter of F3GT1 by 2.45-fold. We infer that bagging treatment increases the kiwifruit anthocyanin content through the bHLH291-F3GT1 pathway. This study not only highlights the potential agricultural applications and commercial value of bagging treatment but also provides new theoretical support for improving fruit coloration and optimizing breeding strategies.