GmSKP1,a Novel S-phase Kinase-associated Protein 1 in Glycine max,Enhancing Resistance Against Phytophthora sojae Infection

Phytophthora root and stem rot of soybean caused by Phytophthora sojae(P.sojae)is a devastating disease that affects soybean[Glycine max(L.)Merr.]all over the world.S-phase kinase-associated protein 1(SKP1)proteins are key members of the SKP1/Cullin/F-box protein(SCF)ubiquitin ligase complex and play diverse roles in plant biology.However,the role of SKP1 in soybean against the phytopathogenic oomycete P.sojae remains unclear.In this study,a novel member of the soybean SKP1 gene family,GmSKP1 which was significantly induced by P.sojae,was reported.The expression of GmSKP1 was simultaneously induced by methyl jasmonate(MeJA),salicylic acid(SA)and ethylene(ET),which might suggest an important role for GmSKP1 of plant in responses to hormone treatments.Functional analysis using GmSKP1 overexpression lines showed that GmSKP1 enhanced resistance to P.sojae in transgenic soybean plants.Further analyses showed that GmSKP1 interacted with a homeodomain-leucine zipper protein transcription factor(GmHDL56)and a WRKY transcription factor(GmWRKY31),which could positively regulate responses to P.sojae in soybean.Importantly,several pathogenesis-related(PR)genes were constitutively activated,including GmPR1a,GmPR2,GmPR3,GmPR4,GmPR5a and GmPR10,in GmSKP1-OE soybean plants.Taken together,these results suggested that GmSKP1 enhanced resistance to P.sojae in soybean,possibly by activating the defense-related PR genes.

Effect of Drought Stress During Flowering Stage on Starch Accumulation and Starch Synthesis Enzymes in Sorghum Grains

Starch content is a key factor affecting sorghum grain quality. The research of sorghum grain starch accumulation and the related synthesis enzyme activities has great signiifcance for understanding the mechanisms of starch metabolisms. The differences between a high and a low starch content sorghum hybrids （Tieza 17 and Liaoza 11, respectively） in grain starch accumulation and the related synthesis enzyme activities were assessed following imposition of water stress during lfowering stage. The total starch, amylase and amylopectin accumulation all decreased at the mid-late stage of grain iflling under drought stress during lfowering stage. The maximum and mean accumulation rates also decreased. During grain iflling, soluble starch synthase （SSS）, granule-bound starch synthase （GBSS）, starch branching enzyme （SBE）, and starch debranching enzymes （DBE） activities were all affected, though differently. Drought stress reduced starch accumulation in a larger extent for Tieza 17 than Liaoza 11. Drought stress during lfowing stage reduced starch synthesis enzyme activities, thus reducing starch accumulation in grains, and the differences between starch components were also demonstrated under drought stress.