Overexpression of the rice phosphate transporter gene OsPT6 enhances tolerance to low phosphorus stress in vegetable soybean

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Low phosphorus (P) availability is a major constraint in the growth and production of vegetable soybean. To improve P efficiency in vegetable soybean, a rice (Oryza sativa L.) phosphate transporter gene, OsPT6, was transferred into the vegetable soybean cultivar ‘NY-1001’ using an Agrobacterium-mediated cotyledonary-node transformation system. OsPT6 was driven by the constitutive cauliflower mosaic virus (CaMV) 35S promoter in the binary vector pCAMBIA3301-OsPT6. Two independent fertile T0 transgenic plants (12PT6-1 and 12PT6-2) were obtained and confirmed by PCR and Southern blotting analyses. The overexpression of the OsPT6 gene of the T2 transgenic plants was detected by quantitative RT-PCR analysis. The tolerance of the T2 transgenic lines overexpressing OsPT6 to low concentrations of phosphate (low-Pi; 10μMPi) was evaluated by hydroponic culture using a modified Hoagland's nutrient solution. The P contents in leaves, stems, and roots of the transgenic plants were significantly higher than those of the non-transformed (NT) plants under the concentrations of both low- and normal-Pi of standard Hoagland's nutrient solution. Under low-Pi stress, the transgenic plants grew better and exhibited significant increases in plant height, root length, root weight, number of pods and seeds, and seed weight per plant compared with the NT plants. Our data indicate that the overexpression of OsPT6 in transgenic vegetable soybean lines improves P accumulation and growth performance and thereby represents a promising approach for the improvement of P efficiency in vegetable soybean.