Genetic Improvement in Crop Phosphorus Efficiency: A Case Study on Purple Acid Phosphatases in Common Bean
Phosphorus (P) deficiency is one of the limiting factors in crop production. Large genetic variations in crop P efficiency have been evaluated, and thus their genetic improvement should be important to address this problem. However, 50–80% of the total P in agricultural soils exists as organic compounds. One strategy for improving crop P nutrition is to enhance root secretion of acid phosphatases (APases) to obtain or remobilize Pi from organic P sources. Purple acid phosphatase (PAP) is a special group of APase with distinct properties. However, the molecular properties and functions of PAPs have not been well studied. In the present study, we found that there are four PvPAPs in common bean, which contain five blocks of conserved amino acid motifs with seven invariant residues. Subsequently, functions of P starvation-induced PvPAP3 were elucidated. Phylogenetic analysis shows that PvPAP1 and PvPAP2, PvPAP3 and PvPAP4 separately belong to high and low molecular mass PAP groups. Expression patterns of the four PvPAPs are obviously different as related to Pi availability. Among them, strong induced expression of PvPAP3 was detected by Pi starvation in roots. Transgenic Arabidopsis plants overexpressing PvPAP3 have superior growth and P uptake when ATP was supplied as the sole external P source. Taken together, our study demonstrated that the P efficiency in common bean could be improved through overexpression of PvPAP3, thus might have great implications for improving crop production on soils lacking of available P which is a serious limitation worldwide.