Molecular mechanism of Abscisic acid regulating bud-break through the NnTIFY10A/B-NnABI5 module in lotus

Abstract The apical bud-break is an important stage in the regulation of lotus (Nelumbo nucifera Gaertn.) flowering. Phytohormones play a key role in the development of plant buds, but the molecular mechanisms underlying the crosstalk between different phytohormone signals, especially Abscisic acid (ABA) and Jasmonic acid (JA), in lotus bud-break remain unclear. In this study, we found that the exogenous application of ABA inhibited the lotus apical bud-break. In addition, the expression of the gene encoding ABSCISIC ACID INSENSITIVE 5 (NnABI5), a crucial regulator of ABA signaling, was gradually downregulated during lotus apical bud-break. The transient overexpression of NnABI5 in lotus and heterologous expression in Arabidopsis thaliana (L.) Heynh. demonstrated that NnABI5 negatively regulates apical bud-break and seed germination. NnABI5 interacted with the JA pathway inhibitors NnTIFF/Y XG 10A/B (NnTIFY10A/B), reducing the binding ability of NnABI5 to response genes EARLY METHIONINE-LABELED 1 (NnEM1) and NnEM6. In contrast, NnTIFY10A/B positively regulates apical bud break and seed germination. Notably, exogenous application of the JA biosynthesis inhibitor DIECA alleviated the inhibitory effect of ABA. In vitro protein degradation assays revealed that ABA could accelerate the degradation of NnTIFY10A/B. In summary, our data reveal the crosstalk of the JA and ABA signaling pathways in lotus apical bud-break, laying a theoretical foundation for understanding the regulation of flowering in this species.