The maize ZmMIEL1 E3-Ligase and ZmMYB83 transcription factor proteins interact and regulate the hypersensitive defense response

Authors: KARRE, SHAILESH - North Carolina State University; KIM, SAET-BYUL - North Carolina State University; SAMIRA, ROZALYNNE - North Carolina State University; Balint-Kurti, Peter

Submitted to: Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2021
Publication Date: 6/1/2021
Citation: Karre, S., Kim, S., Samira, R., Balint Kurti, P.J. 2021. The maize ZmMIEL1 E3-Ligase and ZmMYB83 transcription factor proteins interact and regulate the hypersensitive defense response. Molecular Plant Pathology. https://doi.org/10.1111/mpp.13057.
DOI: https://doi.org/10.1111/mpp.13057

Interpretive Summary: In this study we have identified two proteins that affect the defense response in maize. One mediates protein degradation and one mediates gene expression. We have generated evidence that these two proteins interact and that this interaction is important for their effect on the defense response.

Technical Abstract: The plant hypersensitive defense response (HR), a rapid cell death response at the point of pathogen penetration, is mediated by a class of nucleotide-binding leucine rich repeat (NLR) resistance proteins (R-proteins) which recognize the presence of specific pathogen-derived proteins. Rp1-D21 is an auto-active maize NLR R-gene which triggers HR spontaneously. We previously mapped a number of loci associated with variation in the strength of HR induced by Rp1-D21. In this study we identify the E3 ligase ZmMIEL1 as the causal gene at a modifier locus on chromosome 10. Transient expression of ZmMIEL1 in N. benthamiana reduced HR induced by Rp1-D21, while suppression of ZmMIEL1 gene expression in maize carrying Rp1-D21 increased HR. ZmMIEL1 also suppressed HR induced by another autoactive NLR, the Arabidopsis R-protein RPM1D505V, in the N. benthamiana system. E3 ligases mediate protein degradation via the ubiquitin-mediated proteasome pathway. We demonstrate that the effect of ZmMIEL1 is dependent on the proteasome but also show that levels of Rp1-D21 and RPM1D505V are not reduced when co-expressed with ZmMIEL1 in the N. benthamiana system. By comparison to a similar system in Arabidopsis, we identify ZmMYB83 as a potential target of ZmMIEL1. Suppression of ZmMYB83 expression in maize lines carrying Rp1-D21 suppressed HR. Suppression of ZmMIEL1 expression caused an increase in ZmMYB83 transcript and protein levels in N. benthamiana and maize. Using Co-IP and BiFC assays, we demonstrated that ZmMIEL1 and ZmMYB83 physically interacted. We further demonstrated that ZmMYB83 and ZmMIEL1 regulated the expression of a set of maize very long chain fatty acid (VLCFA) biosynthetic genes which may be involved in regulating HR.