Abstract
Tetep-cytoplasmic male sterility (CMS) was developed through successive backcrosses between subspecies indica and japonica in rice (Oryza sativa L.), which showed abnormal anther dehiscence phenotypes. Whole genome sequencing and de novo assembly of the mitochondrial genome identified the chimeric gene orf312, which possesses a transmembrane domain and overlaps with two mitotype-specific sequences (MSSs) that are unique to the Tetep-CMS line. The encoded peptide of orf312 was toxic to Escherichia coli and inhibited cell growth compared to the control under isopropyl-β-D-1-thiogalactopyranoside (IPTG) induction. The peptide of orf312 contains COX11-interaction domains, which are thought to be a main functional domain for WA352c in the wild abortive (WA-CMS) line of rice. A QTL for Rf-Tetep (restorer-of-fertility gene(s) originating from Tetep) was identified on chromosome 10. In this region, several restorer genes, Rf1a, Rf1b, and Rf4, have previously been reported. Collectively, the interactions of orf312, a candidate gene for Tetep-CMS, and Rf-Tetep, a restorer QTL, confer male sterility and fertility restoration, respectively, which enables a hybrid rice breeding system. Further studies on orf312 and isolation of Rf-Tetep will help to identify the underlying molecular mechanism of mitochondrial ORFs with the COX11-interaction domains.
Highlights
Cytoplasmic male sterility (CMS) has been found in more than 150 flowering plant species [1,2]
We found male sterility in populations that were backcrossed between subspecies of rice, in which the CMS cytoplasm was derived from Tetep, an indica rice variety
Tetep-CMS was obtained through successive backcrosses between Tetep and CP-SLO
Summary
Cytoplasmic male sterility (CMS) has been found in more than 150 flowering plant species [1,2]. The CMS system is usually obtained through successive backcrosses of inter- or intra-subspecies [3]. The cytoplasms from male sterile CMS lines are identified when the nuclear genome is replaced by other cultivars. This maternally inherited trait is widely used in hybrid seed production as a female parent [4]. The fertility of F1 hybrids is restored by the nuclear restorer-of-fertility (Rf ) genes, derived from the male parent [5]. The CMS/Rf system is a good genetic resource for the study of mitochondria–nucleus interactions [3]
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