| BWMK1 was the first reported rice MAPK gene,which was transcriptionally activated by blast fungus infection and wounding. In order to further understand the BWMK1-mediated defense signaling pathway, we identified 7 BWMK1 interacting genes by yeast two-hybrid system, designated BWIP1-BWIP7. BWIP4 and BWIP2 were selected for further functional characterization. BWIP4 encodes a putative phosphate transporter (OsPT8), but BWIP2 shows no hits to known functional groups using the BLAST search.Through Agrobacterium mediated transformation method, RNAi constracts pANDA-BWIP4 and pANDA-BWIP2, overexpression constracts NCGR-1300-BWIP4 and pCAMBIA1301-BWIP2 were transformed into the Japonica cultivar Nipponbare,and the 35 lines,32 lines,136 lines and 108 lines had been abtained respectively.The GUS assay and PCR results showed that the target genes has been intergrated into the receptor. Further expression analysis confirmed that the target genes has been overexpressed and down-regulated in the overexpression and RNAi transgenic plants. The disease resistance of these transgenic lines to bacterial blight pathogen Xanthomonas oryzae pv.oryzae (Xoo) were evaluated. The results showed that both the RNAi lines of BWIP4 and BWIP2 enhanced resistance to Xoo, in contrary, the over-expression lines of BWIP4 and BWIP2 were more susceptible to Xoo than the wide type. These results showed that BWIP4 and BWIP2 were negative regulators for the resitance to the rice bacterial blight pathogen.The Pi content and the number of new roots were assayed in BWIP4 overexpression plants,grown in nutrient solutions with Pi-deficiency and Pi-sufficiency.The resultes showed that the expression level of BWIP4 in rice was significantly enhanced by Pi-deficiency. The number of new roots in BWIP4-overexpression plants were much more than the control at Pi-deficiency treatment. The Pi content of BWIP4-overexpression plant leaves were much higher than the Japonica cultivar Nipponbare.
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