Jasmonate Signal Receptor Gene Family ZmCOIs Restore Male Fertility and Defense Response of Arabidopsis mutant coi1-1

Abstract

Jasmonates (JAs) play an important role in many developmental processes, such as root growth, leaf senescence, male fertility, and defense responses against insects and pathogens. The F-box protein COI1, which plays a central role in JA signal transduction, perceives the JA signal and is required for all the JA-mediated defense responses against biotic and abiotic stresses. JA signaling elements including COI1 have been extensively investigated in Arabidopsise. However, the elements of the JA signaling pathway in maize are largely unknown. In this study, we identified four F-box protein genes from the maize genome, which share high homology with AtCOI1, designated as ZmCOI1a, ZmCOI1b, ZmCOI1c, and ZmCOI2, collectively ZmCOIs. To test whether or not the homologous genes of maize are functionally conservative in JA signaling, we over-expressed ZmCOIs in the Arabidopsis coi1-1 mutant. The results showed that over-expression of ZmCOI1a, ZmCOI1b or ZmCOI1c in the coi1-1 mutant resulted in the restoration of male fertility, indicating successful complementation of coi1-1 sterility by ZmCOI1a, ZmCOI1b, and ZmCOI1c. However, ZmCOI2 was not able to restore male fertility of the mutant, indicating that ZmCOI2 has a function diverged from JA signaling. Furthermore, over-expression of the ZmCOI1a, ZmCOI1b, and ZmCOI1c genes, except ZmCOI2, which, in the coi1-1 mutant, caused restoration of resistance to the leaf pathogen Botrytis cinerea and the soil-borne pathogen Pythium aristosporum. In addition, a set of JA-dependent genes are highly induced by wounding in the transformants of ZmCOIa, ZmCOI1b, and ZmCOI1c, but not inducible in transformants of ZmCOI2 or in the coi1-1 mutant, indicating that ZmCOIa, ZmCOI1b, and ZmCOI1c, except ZmCOI2, which can compensate coi1-1 mutation of Arabidopsis for the stress defense response. Putting all the data together, our results suggested that ZmCOIa, ZmCOI1b, and ZmCOI1c, but not ZmCOI2, act as AtCOI1 orthologues in maize for JA signal transduction.