The Function And Regulation Mechanism Of TaSTP3 And TaSTP6 In Wheat Susceptibility To Stripe Rust

Pathogen infection triggers alteration of sugar transport in host plants for improving pathogen access to nutrients from host cells to survive.Uptake,exchanges,and competition for sugar especially at plant-pathogen interfaces are controlled by sugar transporters.However,the molecular mechanism by which host sugar transporters are manipulated by fungal pathogens for nutrient uptake is poorly understood during plant-fungal interaction.Pst is an obligate biotrophic fungus that acquires nutrients through specialized feeding structures called“haustoria.”Haustoria are fungal organs specific to biotrophic pathogens that form intimate interactions with the host cell to absorb nutrients for pathogens growth.Control over nutrient flux from the plant to the pathogen is a potential strategy to limiting the growth of stripe rust.Understanding sugar transport and distribution between wheat and Pst is important for developing effective disease management strategies.Based on this,this paper carries out the following research:1. To gain a comprehensive view of the distribution of sugar transport proteins(STPs)in wheat,we used the sequences of Os STPs and At STPs to search against the wheat genome database(Ensembl Plants)with BLAST.In total,79 STPs were identified in the wheat genome.In order to identify Pst-responsive Ta STPs in wheat,we firstly searched transcriptomic data from the exp VIP.The results showed that the transcript levels of Ta STP3,Ta STP6,Ta STP13,Ta STP25 and Ta STP26 were significantly increased during Pst infection.q RT-PCR results revealed that the transcript levels of Ta STP3,Ta STP6,Ta STP13,Ta STP25and Ta STP26 were induced during Pst infection.Ta STP25 and Ta STP26 showed no significant difference in expression.The transcript levels of Ta STP3,Ta STP6 and Ta STP13were significantly increased.The results showed that a series of sugar transporter genes were up-regulated in wheat-Pst interaction.2. The expression of all three Ta STP3 copies was sharply induced in wheat infected by Pst.Subcellular localization and heterologous complementation revealed that Ta STP3 is a plasma membrane-localized H~+/hexose transporter.Transient silencing by VIGS observed a clear reduction uredium phenotype and limit fungal development of Pst in wheat leaves.Stable transgenic by RNAi in wheat further demonstrated that silencing of Ta STP3 genes might limit fungal development.Overexpression of Ta STP3 in wheat observed a clear increase uredium phenotype and promote fungal development of Pst in wheat leaves.Overexpression of Ta STP3 revealed that Ta STP3 play a positive role in wheat susceptibility to Pst.Five candidate proteins were identified to bind the promoter of Ta STP3 by yeast-one-hybrid(Y1H)assay.Using dual-luciferase(LUC)reporter system,we demonstrate that the Ta WRKY61 and Ta WRKY82 protein is able to activate the expresion of Ta STP3.In addition,Ta WRKY17,Ta WRKY19 and Ta-PHR1 had no significant effect on the expression of Ta STP3 promoter.Together,our data provide that Ta STP3 play a positive role in wheat susceptibility to Pst and the expression of Ta STP3 is activated by Ta WRKY61 and Ta WRKY82.3. Upregulation of Ta STP6 transcripts occurred in wheat leaves either inoculated with Pst or treated with ABA.Having identified the presence of a cluster of ABRCs were identified in the Ta STP6 promoter region by analysis.Ta STP6np-GUS fusions in transgenic Arabidopsis were activated by ABA treatment.Previous studies found that ABA levels also increased in plants infected by pathogen caused concern.We found that Pst infection also resulted in increased accumulation of ABA.Upregulation of Ta STP6 was possibly mediated by ABA in wheat leaves inoculated with Pst.Transient silencing Ta STP6 expression by BSMV-VIGS knockdown reduced wheat susceptibility to Pst,decreased fungal biomass and restricted fungal development.In addition,overexpression of Ta STP6 promoted Arabidopsis susceptibility to powdery mildew,had more conidiophores per colony and resulted in increased Glc accumulation in the leaves.Transient expression analysis in Nicotiana benthamiana leaves and wheat leaf protoplasts showed that Ta STP6 is localized to the plasma membrane.Heterologous expression in Saccharomyces cerevisiae revealed that Ta STP6 is a hexose/H~+symporter.Yeast two hybrid(Y2H)and bimolecular fluorescence complementation(Bi FC)validated oligomerization of Ta STP6.During Pst infection of wheat,ABA levels increase and the upregulated expression of Ta STP6,possibly through the action of an ABA responsive transcription factor,results in enhanced import of apoplastic hexoses into Pst-infected cells.Accumulation of cytoplasmic hexose promotes infection of Pst due to sufficient carbon supply by the absorption of haustoria.