Rice annexin OsANN4 interacting with OsCDPK24, reduces root aerenchyma formation by modulating H₂O₂ under ABA treatment

Abstract

34Plant annexins are calcium-and lipid-binding proteins that have multiple functions, 35 and a significant amount of research on plant annexins has been reported in recent 36 years. However, the functions of annexins in diverse biological processes in rice are 37 largely unclear. Herein, we report that OsANN4, a calcium-binding rice annexin 38 protein, is a substrate for OsCDPK24, and the OsANN4 phosphorylation site is the 39 13th serine, which is a key site for phosphorylation. Most strikingly, abscisic acid 40 (ABA) promotes the interaction between OsANN4 and OsCDPK24. Moreover, 41 knocking down OsANN4 by RNA interference resulted in visible and invisible 42 phenotypes with exogenous ABA treatment, such as shorter shoots of seedlings, less 43 lateral roots, earlier root aerenchyma formation and so on. The further analyzed 44 results showed that decreased superoxide dismutase (SOD) and catalase (CAT) 45 activity of the RNAi lines, which control H2O2 accumulation for redox homeostasis, 46 and further promoted earlier aerenchyma formation of the root. These results suggest 47 that a proposed molecular mechanism exists between OsANN4 and H 2 O 2 production 48 to response ABA. 49