Functional Analysis Of GmG3PT3 Involvement In Soybean Responses To Phosphorus Deficiency

Soybean is an important grain and oil crop in the world.Phosphorus(P)is an essential macronutrient for plant growth and development.Low P availability in soils restricts soybean yield and quality directly.Plants have evolved a series of physiological,biochemical and molecular mechanisms to promote phosphate(Pi)acquisition and reutilization.GmG3PT3 was selected from a Pi starvation-induced soybean suppression subtractive hybridization(SSH)library,encoding a sugar-phosphate/anion antiporter.In this study,the transgenic soybean plants with modified expressions of GmG3PT3 and Arabidopsis plants over-expressing GmG3PT3 have been employed to explore the functions of GmG3PT3 in soybean responses to P deficiency.The main results are shown as follows:1)Phylogenetic analysis revealed that the similarity of G3PTs were low between plants and bacteria,but high in planta.The plant G3PTs could be divided into three subfamilies.Among them,GmG3PT3 belonged to the II subfamily.An alignment of putative amino acid sequences of G3 PTs from various crops revealed that there were many conserved residues with high similarity,suggesting that the function of G3 PTs in different crops might be conserved.2)Yeast heterologous expression verified that GmG3PT3 could transport glycerol-3-phosphate(G3P)and Pi,and the affinity for G3P was much higher than Pi.3)The expression of GmG3PT3 was induced by Pi starvation in young leaves,roots and the stem of soybean seedlings,especially in roots.Under low P conditions,the relative expression of GmG3PT3 in roots was highest in root hairs and lowest in the root tip.The expression of GmG3PT3 in shells was higher than that in seeds at early podding stage,but its expression in seeds increased with the increasing maturity of soybean.4)GUS staining driven by the promoter of GmG3PT3 showed that GmG3PT3 almostabsent in the leaves and root tips of transgenic Arabidopsis plants,but mainly observed in the formation of lateral roots.Along with the elongation of lateral roots,it was mainly expressed in the stele and root hair zone.The results from transgenic soybean plants were similar to Arabidopsis,the GmG3PT3 expression was mainly found in the root mature zone during lateral root formation.5)Overexpression of GmG3PT3 in Arabidopsis promoted plant growth,increased total root length and root hair density.Under low P conditions,overexpression of GmG3PT3 significantly increased root biomass and total P content.6)Overexpression of GmG3PT3 in soybean promoted root growth,increased root hair density,total root length and area,meanwhile increased soybean biomass and total P content.The transgenic soybean with RNA interference of GmG3PT3 showed the opposite phenotype,including significantly inhibited root growth,decreased root hair density,total root length and area,biomass and total P content.In addition,under high P conditions,the expression of GmG3PT3 changed the soluble Pi redistribution.7)Overexpression of GmG3PT3 increased the yield of transgenic soybeans,but had no effect on hundred-grain weight and oil content;RNA interference of GmG3PT3 not only significantly decreased the yield of the transgenic soybean plant,but also decreased hundred-grain weight and oil content.In conclusion,the expression of GmG3PT3 could regulate plant root growth,Pi redistribution,total P content and yield,and therefore plays important roles in soybean adaptation to P deficiency.