A maize Cytochrome b-c1 complex subunit protein ZmQCR7controls variation in the hypersensitive response

Authors: HE, YIJIAN - North Carolina State University; KIM, SAET-BYUL - North Carolina State University; Balint-Kurti, Peter

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2018
Publication Date: 1/29/2019
Citation: He, Y., Kim, S., Balint Kurti, P.J. 2019. A maize Cytochrome b-c1 complex subunit protein ZmQCR7controls variation in the hypersensitive response. Planta. 249:1477-485.

Interpretive Summary: In this manuscript we show that a component of the mitochondrial electron transport chain is important for controlling a form of programed cell death in maize that is associated with the defense response, known as the hypersensitive response (HR). We identify naturaly-occurring variants that show differential ability to suppress HR.

Technical Abstract: We previously identified a QTL at 3,545,354bp (B73 reference genome V2) on maize chromosome 5 associated with variation in the hypersensitive response (HR) conferred by the autoactive R-gene Rp1-D21. In this study we show that a gene at this locus, GRMZM2G318346 which encodes a Cytochrome b-c1 complex subunit 7 (ZmQCR7), an important part of the mitochondrial electron transport chain, can suppress HR mediated by Rp1-D21 in a transient expression assay. ZmQCR7 alleles from two maize lines, W22 and B73 differ for the encoded proteins at just two sites; amino acid 27 (threonine and alanine in B73 and W22 respectively) and amino acid 109 (Asparagine and Serine) however the B73 allele is much more effective at suppressing HR. We show that variation at amino acid 27 controlled this variation in HR-suppressing effects. We furthermore demonstrate that the B73 allele of ZmQCR7 can suppress HR induced by RPM1(D505V), another autoactive R-gene, and that Arabidopsis homologs of ZmQCR7 also suppress NB-LRR-induced HR. The implications of these findings are discussed.