Function Analysis Of GmPIP1;6and GmAKT2Insoybean Stress Resistance

Soybean (Glycine max L) is an important food and oil crop. Genetic engineering of soybean to improve agronomic performance, herbicide and pest resistance is of great importance for promoting soybean production in the world. On the basis of establishment of efficient soybean transformation system, the function of the soybean aquaporin gene GmPIP1;6and the potassium transporter gene GmAKT2on the improvement of salt and virus tolerance was studied.By optimization of factors involving in soybean transformation, including screening of recipient genotypes, agrobacterium growth condition, and preparation methods of explants, we are able to achieve an overall efficiency of4.5%based on the number of transformed events. The improvement of explant preparation was awarded a national innovation patent.Aquaporins are proposed to have a major role in growth of plants via their impact on root water uptake, growth and leaf gas exchange. GmPIP1;6is associated with control of root hydraulic conductance (Lo) in soybean and is highly expressed in roots as well as reproductive tissues. It is a functional aquaporin when expressed in Xenopus oocytes and is targeted to the plasma membrane in onion epidermis. Treatment with100mM NaCl resulted in reduced expression initially then after3days the expression was increased in root and leaves. Overexpression of GmPIP1;6in soybean via Agrobacterium-mediated soybean transformation system. In normal condition, there was no difference between GmPIP1;6overexpression transgenic soybean plants (GmPIP1;6-Oe) and wild type (WT) control. With100mM NaCl, GmPIP1;6-Oe resulted in enhanced growth, leaf gas exchange and net assimilation compared to WT. GmPIP1;6-Oe plants enhance Na+extrusion and were able to maintain Lo under saline conditions compared to WT. GmPIP1;6-Oe lines grown in the field had increased yield resulting mainly from increased seed size. The general impact of overexpression of GmPIP1;6suggests that it may be a multifunctional aquaporin involved in root water transport, photosynthesis and seed loading.Soybean mosaic virus (SMV) is the most prevalent viral disease in many soybean production areas. Genetic engineering is an effective approach for improving SMV resistance in soybean. The addition of potassium (K4) fertilizer significantly reduced SMV incidence. Analysis of K+channel gene expression indicated that GmAKT2was significantly induced by SMV inoculation in the SMV highly-resistant genotype Rsmv1, but not in the susceptible genotype Ssmvl. GmAKT2overexpression trangenic soybean (GmAKT2-0e) lines were acquired via Agrobacterium-mediated soybean transformation system in our lab. Each independent transgenic lines were verified by Southern blot and qRT-PCR analysis. GmAKT2-Oe on the SMV-susceptible background enhanced the reallocation of K+in soybean plants and increased K+concentrations in young leaves. Most importantly, SMV development was significantly retarded in GmAKT2-Oe transgenic soybean plants. Alteration of K+transporter expression is a novel molecular approach for genetically enhancing SMV resistance in soybean.