In CMSWA lines, WA352 accumulates preferentially in the anther tapetum, thereby inhibiting COX11 function in peroxide metabolism and triggering premature tapetal programmed cell death and consequent pollen abortion.
Plant cytoplasmic male sterility (CMS) results from incompatibilities between the organellar and nuclear genomes and prevents self pollination, enabling hybrid crop breeding to increase yields. The Wild Abortive CMS (CMSWA) has been exploited in the majority of 'threeline' hybrid rice production since the 1970s, but the molecular basis of this trait remains unknown.
Plant mitochondrial genomic transformation is currently infeasible, but CMS gene function can be tested by nuclear transformation of candidate gene(s) fused with a mitochondrial transit signal (MTS)[1,2].
The suppression of the WA352-interacting gene O. sativa COX11(OsCOX11) can produce male sterility (Fig.1).
COX11 proteins are conserved in eukaryotes and function in the assembly of cytochrome c(Cyt c) oxidase (Fig.2).
In yeast, Saccharomyces cerevisiaeCOX11 (ScCOX11) has a role in hydrogen peroxide degradation. COX11 proteins also function in peroxide metabolism and may act as negative regulators of PCD.
OsCOX11 is constitutively expressed (Fig. 3). A. thaliana AtCOX11 (287 residues), which shares 80% identity with OsCOX11, also interacted with WA352 (Figure 4a). Y2H deletion assays identified two regions (residues 218–292 and 294–352) of WA352 that interact with OsCOX11 (Fig. 4a). Similarly, a 37-residue sequence (184–220) in the highly conserved region of OsCOX11 confers the WA352 binding (Fig. 4b,c). A bimolecular fluorescence complementation (BiFC) assay confirmed the mitochondrial localization of OsCOX11 and its in vivo interaction with WA352 (Fig. 4d and Fig. 5).
CMS-related cytoplasmic-nuclear incompatibility is driven by a detrimental interaction between a newly evolved mitochondrial gene and a conserved, essential nuclear gene.
Labs working on this gene
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Key Laboratory of Plant Functional Genomics and Biotechnology of Guangdong Provincial Higher Education Institutions, College of Life Sciences, South China Agricultural University, Guangzhou, China.
College of Forestry, Guangxi University, Nanning, China.
State Key Laboratory of Biocontrol, Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, China.
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