Characterization and expression analysis of key abscisic acid signal transduction genes during kiwifruit development

Abstract

To characterise the regulation of abscisic acid (ABA) signal transduction during fruit development and ripening, we investigated the key genes involved in the ABA signalling pathway in kiwifruit (Actinidia chinensis), including 18 AcPYLs genes encoding ABA receptors, 7 AcPP2Cs genes encoding type 2C protein phosphatases, and 7 AcSnRK2s genes encoding members of the SNF1-related protein kinases 2 family identified in the kiwifruit reference genome. AcPYLs, AcPP2Cs, and AcSnRK2s from kiwifruit are putative homologues of the corresponding Arabidopsis and tomato proteins. Phylogenetic analysis revealed that AcPYLs and AcSnRK2s clustered into three subfamilies. Transcript levels indicated that the expression pattern of AcNCED4 was consistent with the ABA content of the pulp during kiwifruit development. Furthermore, the ABA content of the axile placenta was higher than that of the sarcocarp in kiwi pulp, and the expression of most ABA signal transduction genes, including AcPYLs, AcPP2Cs, and AcSnRK2s, was more predominant in the axile placenta. Moreover, AcPP2C3 was localised in the nucleus and could interact with all AcPYLs and AcSnRK2s in an ABA-independent manner, as revealed by subcellular localisation and yeast two-hybrid assays. These findings enhance our understanding of ABA signal transduction genes in kiwis, and provide the necessary background for further exploration of the molecular mechanisms at play during kiwifruit development.