An ABA-induced sugar transporter gene TaSTP1 reinforces wheat susceptibility to Puccinia striiformis

Pathogens, whatever their types, develop at the expense of the nutrients generated by host and it is largely assumed that classical sources turn into sinks when colonized by pathogens. Sugar appears to be the major carbon and energy source transferred from the host to pathogens. Uptake, exchanges and competition for sugar, at biotrophic interfaces, are controlled by membrane transporters and their regulation patterns are essential in determining the outcome of plant-fungal interactions. However, mechanisms of transport and transporters involved in carbon partitioning between organisms are still poorly understood.
In this study, a wheat sugar transporter protein (STP) gene, TaSTP1, was cloned from a wheat-Puccinia striiformis f. sp. tritici (Pst) interaction cDNA library. Transcripts of TaSTP1 were up-regulated in wheat leaves that were infected by Pst or had experienced exogenous ABA and certain abiotic treatments. Heterologous mutant complementation in Saccharomyces cerevisiae revealed that TaSTP1 transports a broad-spectrum monosaccharides including glucose, fructose, mannose and galactose. Transient expression in Nicotiana benthamiana and Arabidopsis protoplasts suggested that TaSTP1 is localized in plasma membrane. Yeast two hybrid and bimolecular fluorescence complementation (BiFC) validated oligomerization of TaSTP1. Knocking down TaSTP1 using the barley stripe mosaic virus-induced gene silencing system reduced the susceptibility of wheat to the Pst virulent pathotype CYR31. Hyphal abnormality was significantly observed in VIGS plants. These results suggest that TaSTP1 may directly or indirectly participate in sugar transport in the wheat-Pst interactions and exert influence on suagr supply of Pst.