Identification of phosphate-starvation-inducible gene BnIPS1 in Brassica napus

TPSI1/Mt4 family genes are a class of genes induced dramatically by Pi starvation, and are involved in Pi allocation in plants. Its members have been isolated from many plant species, but none has been reported in Brassica napus. Here, we isolated two novel members of TPSI1/Mt4 family from B. napus, which were referred to as BnIPS1;1 and BnIPS1;2. The two genes are 592 and 557 bp long, respectively, and share 91 % sequence identity. They are all intronless, and contain numerous short open reading frames and a conserved 22-nucleotide sequence partially complementary to miR399. Expression analysis revealed that the two genes were induced strongly by Pi starvation and weakly by osmotic stress and salinity. The induction of the two genes is rapid and durative in the absence of Pi and is repressible upon Pi resupply. Furthermore, BnIPS1;1 promoter (−1,459/+42 relative to transcription start site) was isolated and fused to reporter gene GUS. The P BnIPS1;1 :GUS construct was introduced into Arabidopsis, and intensive GUS staining was observed in Pi-starved plants. These results further our understanding of TPSI1/Mt4 family genes, and demonstrate that BnIPS1;1 and BnIPS1;2 can be used as tool for investigating Pi-starvation signaling in B. napus and BnIPS1;1 promoter can be used as inducible promoter for cultivating P-efficient crops.