Expression of pepper cytoplasmic male sterility-associated open reading frame, orf507 in transgenic tobacco plants

Abstract

Cytoplasmic male sterility (CMS) is a mitochondrial inherited trait that prevents a flower from producing normal pollen grains. CMS has widely been used to produce F1 hybrid seed in pepper. Though the orf507 gene is known to be associated with CMS in peppers, definitive and direct evidence that ORF507 induces male sterility is still lacking. In this study, a set of chimeric constructs were developed to confirm the hypothesis that ORF507 protein directly causes male sterility in tobacco. Tapetum-specific promoter TA29, mitochondrial transit sequence yeast coxIV pre-sequence, orf507 and green fluorescent protein (GFP) gene were cloned sequentially and designated as TCOGN (TA29-coxIV pre-sequnce-orf507-GFP-nos terminator). For developing control vectors, orf507 was cloned under TA29 promoter without coxIV pre-sequence (TOGN) or orf507 was cloned with or without coxIV pre-sequence under the constitutive CaMV35S promoter (SCOGN and SOGN). The four constructs (TCOGN, TOGN, SCOGN, and SOGN) were used to transform tobacco using leaf disk transformation mediated by agrobacterium. At flowering stage, transgenic plants will be scored for pollen production and viability. This study is expected to provide evidence that the expression of orf507 gene in the tapetum might be responsible for male sterility in pepper.