Agrobacterium rhizogenes transformed soybeans with AtPAP18 gene show enhanced phosphorus uptake and biomass production

Low-phosphorus stress is a challenging factor in limiting plant development. Soybean is cultivated in soils often low in phosphorus. However, on average 65% of total P is in the form of organic phosphates, which are unavailable to plants unless hydrolyzed to release inorganic phosphate. One approach for enhancing crop P acquisition from organic P sources is boosting the activity of acid phosphatases (APases). This study seeks to understand the role of an Arabidopsis (Arabidopsis thaliana) purple APase gene (AtPAP18) in soybean. Thus, the gene was isolated and a final vector (AtPAP18/pK7GWG2D) was built. Composite soybean plants were created using Agrobacterium rhizogenes-mediated transformation. A. rhizogenes K599 carrying the AtPAP18/pK7GWG2D vector with egfp as a reporter gene was used for soybean hairy root transformation. Analysis of Egfp expression detected fluorescence signals in transgenic roots, whereas there was no detectable fluorescence in control hairy roots. The enzyme assay showed that the APase activity increased by 2-fold in transgenic hairy roots. The transformed hairy roots displayed an increase in plant soluble P and total P contents, as compared with the control plants, leading to improved biomass production. RT-PCR analysis revealed high expression levels of AtPAP18 in transformed hairy roots. It is noteworthy that these primers amplified no PAP18 transcript in control hairy roots. Taken together, the findings demonstrated that overexpression of the AtPAP18 gene offers an operative tactic to reduce the utilization of inorganic phosphorus (Pi) fertilizer through increased acquisition of soil Pi, especially improving the crop yield on soils low in available P.