Candidate Gene Analysis of the Restorer-of-fertility Gene in Pepper and Transgenic Expression of the Pepper CMS Associated Gene orf507 in Nicotiana benthamiana

Abstract

Cytoplasmic-genic male sterility (CGMS) has been widely used to produce hybrid seeds. Plant CGMS is due to genetic incompatibility between mitochondria and nucleus and is typically associated with the abnormal chimeric gene of mitochondria. Although the candidates for CMS-associated mitochondrial gene and Restorer-of-fertility (Rf) gene were proposed, direct evidence of true Rf gene identifying is still lacking. Thus, development of Rf candidate markers and transgenic expression of CMS related gene in tobacco were performed in this study. In the first chapter, expression and sequence of Rf candidates, CDS1, CDS2, CDS3 and CaPPR6 were conducted in chili pepper Bukang and Chungyang CMS and restorer lines and sweet pepper MSGR-A and SPR03. Among candidate genes, only CDS3 showed specific expression in fertile lines. Molecular markers were developed based on SNPs and InDel of each candidate and applied to Rf segregation population of sweet pepper. As a result, newly developed markers showed reverse results between chili pepper and sweet pepper lines. This result suggests that MSGR-A and SPR03 have different type of Rf co-segregated region compared to chili pepper. In the second chapter, to check the hypothesis that ORF507 is sufficient to induce male sterility in plants, the cDNA of orf507 was cloned in frame with mitochondria transit sequence, coxIV, and was expressed under tapetum-specific promoter TA29 in tobacco plants. But transgenic tobacco plants carrying orf507 cloned under the tapetum specific promoter with mitochondrial transit sequence did not show male sterility.