A wheat PI4K gene whose product possesses threonine autophophorylation activity confers tolerance to drought and salt in Arabidopsis

Phosphoinositides are involved in regulation of recruitment and activity of signalling proteins in cell membranes. Phosphatidylinositol (PI) 4-kinases (PI4Ks) generate PI4-phosphate the precursor of regulatory phosphoinositides. No type II PI4K research on the abiotic stress response has previously been reported in plants. A stress-inducible type II PI4K gene, named TaPI4KII, was obtained by de novo transcriptome sequencing of drought-treated wheat (Triticum aestivum). TaPI4KII, localized on the plasma membrane, underwent threonine autophosphorylation, but had no detectable lipid kinase activity. Interaction of TaPI4KII with wheat ubiquitin fusion degradation protein (TaUDF1) indicated that it might be hydrolysed by the proteinase system. Overexpression of TaPI4KII revealed that it could enhance drought and salt stress tolerance during seed germination and seedling growth. A ubdk7 mutant, identified as an orthologue of TaPI4KII in Arabidopsis, was sensitive to salt, polyethylene glycol (PEG), and abscisic acid (ABA), and overexpression of TaPI4KII in the ubdk7 mutant compensated stress sensitivity. TaPI4KII promoted root growth in Arabidopsis, suggesting that TaPI4KII might enhance stress resistance by improving root growth. Overexpression of TaPI4KII led to an altered expression level of stress-related genes and changes in several physiological traits that made the plants more tolerant to stress. The results provided evidence that overexpression of TaPI4KII could improve drought and salt tolerance.