The Arabidopsis major leaf ferredoxin Fd2 regulates immune responses and mediates Harpin-induced hypersensitive reaction.
M. WANG (1), K. Zhang (2), L. Rui (3), M. Bellizzi (2), D. Tang (3), Z. Wei (4), G. Wang (1) (1) Ohio State University, U.S.A.; (2) Ohio State University, U.S.A.; (3) Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, China; (4) Plant Health Care, Inc., U.S.A.

Ferredoxins, the major distributors for transferring electrons to various acceptor systems in the chloroplast, contribute to redox regulation and antioxidant defense. However, the function of this kind of small [2Fe-2S] cluster-containing proteins in plant immunity is still unknown. In this study, we found that the knockout mutant of the major leaf ferredoxin (Fd2-KO) confers enhanced susceptibility to both bacterial and fungal pathogens. Fd2-KO accumulates higher levels of ROS before and after flg22 treatment than the wild-type Nossen. However, the transcription of PR genes in Fd2-KO is significantly lower than wild type after P. syringae infection. The expression of Fd2 is reduced by P. syringae infection, which implies that Fd2 might be the target of pathogens for pathogenesis. Interestingly, we found that Fd2 interacts with FIB4, the fibrillin localized in thylakoid membrane, and both proteins bind to harpin, HrpN of Erwinia amylovora. The transcription of both Fd2 and FIB4 is up-regulated after HrpN treatment and their transient expression in Nicotiana benthamiana enhances the hypersensitive reaction (HR) induced by HrpN. In addition, Fd2, rather than FIB4, is delivered to the nucleus by stromules from chloroplasts, and HrpN treatment causes Fd2 released from the chloroplast. Taken together, our results suggest that Fd2 represents an important component involved in both plant immunity and harpin-induced HR.

Abstract Number: P17-635
Session Type: Poster