Functional Analysis Of PpBOR Genes

Boron is an important micronutrient for plant development. Suboptimal soil boron content is one of the limiting factors in agriculture and affects the yield of major crops in the world. Previous researches have proved that members of the Arabidopsis BOR family are efflux transporters of boron, for example, AtBORl is involved in xylem loading of boric acid under low boron condition. There are two AtBORl orthologs in the non-vascular plant Physcomitrella patens genome, named as PpBORl and PpBOR2.To investigate the function of BOR genes in non-vascular plants, we examined the expression patterns of PpBORl and PpBOR2, and generated konckout and overexpression mutants of these two gene, respectively. Our results showed that the expression levels of both PpBOR1and PpBOR1were very low in protonema and leafy gametophore, but comparably high in rhizoids. The fact that PpBOR1could be induced by high boron treatment suggested that PpBOR2might play a role in response to high boron. Phenotypes of PpBOR1mutants also support this assumpiton with the knockout mutants exhibited lower resistance to high boron stress and overexpression lines were more resistant.