Abstract
The plastid genome contains more than one hundred genes and the expression is regulated depending on cell- and plastid-types. Sigma factors determine the specificity of the eubacteria-type plastid RNA polymerase (PEP), but roles of each sigma factor for chloroplast gene expression remain largely unknown. During oilseed development, chloroplasts play a critical role for the fatty-acid biosynthesis. We focused on this chloroplast function in Arabidopsis, and searched for sigma factors (SIG1-6) which involve in this, by using sig mutants. As a result, greening of seed chloroplasts was inhibited in newly identified sig2-2 and sig6-2 mutants, whereas thylakoid development was only inhibited in sig6-2. In situ hybridization analysis showed the expression of SIG2 and SIG6 in developing seed embryo, and measurement of fatty-acids contents showed the reduction of triacylglycerols (TGs) and the alteration of constitution of TGs. These data suggest differential roles of SIG2 and SIG6 for oilseed development.
