Functional Analysis Of GmAAT Resistant To Soybean Cyst Nematode At Soybean Rhg1

Soybean cyst nematode(SCN;Heterodera glycines Ichinohe),is the most economically damaging disease of soybean worldwide.Breeding resistant cultivars is one of most economical and efficient methods to control this disease.In this study,we improve the method for counting the cysts and investigate the function of Rhg1,one of important loci with resistance to soybean cyst nematode(SCN).1.The evaluation of resistance to SCN is mainly based on the number of cysts on soybean roots.Therefore,a high-throughput and accurate counting of cysts is an important prerequisite in the study of SCN,which is labor-intensive and tedious.The fluorescence imaging technology has been used to count the cysts using Halogen or Xenon as the excitation light source.However,because of the low energy of excitation light source,this technology only has good counting results on fresh white cysts rather than old brown cysts that have weak fluorescence.In this study,we used laser as the excitation light source and explored suitable photo conditions and counting parameter.The results showed that,under these conditions,the brown cysts can also be obtained with high contrast and clear pictures.This method of cyst-counting can be conducted in an accurate and high-throughput way.2.Rhg1(resistance to Heterodera glycines 1)is one of important quantitative trait loci(QTL)that contributes to resistance against soybean cyst nematode.Previously studies showed that Rhg1 consisted of three responsible genes,where Glyma.18G022400(GmAAT)is one of them.However,until now,the function of GmAAT remains largely unknown.In this study,we preliminarily investigated the function of GmAAT.Sequence analysis showed that GmAAT encoded a predicted amino acid transporter.Histochemical analyses of the transgenic Arabidopsis and transgenic soybean hairy roots show that GmAAT was involved in the transportation of amino acids between the organs of the plant via the vascular system.A sensitivity assay showed that overexpression of GmAAT could enhance the tolerance of transgenic Arabidopsis and soybean to excess amounts of different amino acids,which indicated GmAAT might be involved in glutamate(Glu)transportation in vivo.Up-regulation of GmAAT could activate the JA pathway in soybean.Treatment with a JA biosynthesis inhibitor reduced the resistance provided by the Rhg1-containing PI88788 to SCN,which suggested that the JA pathway might play a role in Rhg1-mediated resistance to SCN.