Molecular cloning and characterization of phosphorus starvation responsive genes in common bean (Phaseolus vulgaris L.)

Common bean (Phaseolus vulgaris L.) is one of the most important food legumes in the world and its production is limited by low phosphate (Pi) availability in many arable soils. To gain better insight into the molecular mechanisms by which common bean adapts to low Pi availability, we generated a suppression subtractive cDNA library to identify genes involved in P starvation responses. Over 240 putative Pi starvation-responsive genes were identified. The identified clones were sequenced and BLASTx/BLASTn analysis revealed an array of 82 genes showing a high degree of sequence homology to known and unknown proteins in the database. Transcript abundance of seven genes representing different functional categories was examined by Northern blot analysis. Six genes were strongly induced/enhanced under Pi deficiency confirming the results of SSH. Full length cDNAs for three genes, representing PvIDS4-like, PvPS2, and PvPT1 were cloned and characterized. The open reading frame (ORF) of PvIDS4-like encodes a 281-amino acid protein, containing a SPX domain. The ORF of PvPS2 gene encodes a 271-amino acid protein coding for a putative phosphatase. The PvPT1 encodes a 531-amino acid protein exhibiting high homology with high affinity Pi transporters. Expression patterns of these three genes in relation to Pi availability were evaluated with two contrasting genotypes (P-inefficient Dor364 and P-efficient G19833). Both Northern and RT-PCR results showed enhanced accumulation of phosphate transporters and phosphatases in P-efficient genotype, implying that in addition to modified root morphology and architecture, increased P transport and phosphatases activity might contribute to efficient Pi acquisition and translocation in G19833 common bean genotype under limited Pi conditions.