Responses Of Soybean Malate Enzymes And Malate Synthase Genes To Low Phosphorus Stress

Phosphorus(P)is one of the essential nutrient elements for plant growth.However,Pi availability in many soils is limiting,which therefore inhibits crop production.Plants have developed many strategies to adapt the P deficiency.Among them,regulation of malate synthesis and secretion is one of the important mechanisms of crop tolerance to low P stress.Studies have been showing that Malate enzyme(ME)and malate synthase(MS)are involved in the malate metabolism in plants.Therefore,in the present study,we investigate the malate concentration and malate exudation from soybean roots and identified 10 GmME and 3 GmMS genes in soybean genome.The results are listed as following:1.Malate concentration in different parts of soybean was deferentially regulated by low P stress.Low P stress significantly increased root malate concentration and root malate exudation.In contrast,malate concentration in old leaves was remarkably reduced.Interestingly,no significant differences were observed in the malate concentration of young leaves.2.Totally 3 GmMS genes were found in soybean genome,which was sub-grouped into 2clades.The conserved motif and the conserved domain of these three GmMSs shared high similarity.The real-time PCR results showed that P deficiency up-regulated the expression of GmMS1 in young leaves,but down-regulated its expression levels in both old leaves and roots.Moreover,P deficiency increased the expression of GmMS3 in old leaves,but had little effects on its expression in both young leaves and roots.3.There were 10 GmME genes were found in soybean genome.Except for GmME5,all the other GmME gene members had similar conserved motifs and conserved domains.The real-time PCR reveals that P deficiency significantly up-regulated the expression of GmME3 in young leaves and the expression of GmME4 in roots,while down-regulate the expression of GmME6 in old leaves.Additionally,the expression of all the other GmME genes were not significantly affected.The expression pattern of GmME4 response to low P stress was further characterized.4.It was showed that the expression of GmME4 was significantly up-regulated 9 days after P deficiency.Moreover,the expression level of GmME4 in soybean roots was increased with the decreasing of Pi availability,and reached the highest at 5 u M of P.