Characterization of the promoter of phosphate transporter TaPHT1.2 differentially expressed in wheat varieties

TaPHT1.2 is a functional,root predominantly expressed and low phosphate(Pi) inducible high-affinity Pi transporter in wheat,which is more abundant in the roots of P-efficient wheat genotypes(e.g.,Xiaoyan 54) than in P-inefficient genotypes(e.g.,Jing 411) under both Pi-deficient and Pi-sufficient conditions.To characterize TaPHT1.2 further,we genetically mapped a TaPHT1.2 transporter,TaPHT1.2-D1,on the long arm of chromosome 4D using a recombinant inbred line population derived from Xiaoyan 54 and Jing 411,and isolated a 1,302 bp fragment of the TaPHT1.2-D1 promoter(PrTaPHT1.2-D1) from Xiaoyan 54.TaPHT1.2-D1 shows collinearity with OsPHT1.2 that has previously been reported to mediate the translocation of Pi from roots to shoots.PrTaPHT1.2-D contains a number of Pi-starvation responsive elements,including P1BS,WRKY-binding W-box,and helix-loop-helix-binding elements.PrTaPHT1.2-D1 was then used to drive expression of β-glucuronidase(GUS) reporter gene in Arabidopsis through Agrobacterium-mediated transformation.Histochemical analysis of transgenic Arabidopsis plants showed that the reporter gene was specifically induced by Pi-starvation and predominantly expressed in the roots.As there is only one SNP between the TaPHT1.2-D1 promoters of Xiaoyan 54 and Jing 411,and this SNP does not exist within the Pi-starvation responsive elements,the differential expression of TaPHT1.2 in Xiaoyan 54 and Jing 411 may not be caused by this SNP.