Targeted knockout of PpASCL, an anther-specific chalcone synthase-like gene, supports role in sporopollenin biosynthesis in the moss Physcomitrella patens.

Abstract

The anther-specific chalcone synthase-like (ASCL) gene of Physcomitrella patens, PpASCL, has been implicated in the biosynthesis of sporopollenin, the main constituent of exine and perine, the two outermost layers of the moss spore cell wall. Targeted knockouts of PpASCL were produced and the resulting mutants characterized. Knockout plants developed normally until late in sporophytic development, when the spores produced were aberrant and non-viable. The development of the spore cell wall appeared to be arrested early in microspore development, resulting in small, collapsed spores with irregular surface morphology. These results suggest that PpASCL plays an important role in the proper formation of the exine layer, and is required for the maturation and viability of moss spores.