Improving rice tolerance to potassium deficiency by enhancingOsHAK16p:WOX11-controlled root development

Summary Potassium (K) deficiency in plants confines root growth and decreases root‐to‐shoot ratio, thus limiting root K acquisition in culture medium. A WUSCHEL ‐related homeobox ( WOX ) gene, WOX 11 , has been reported as an integrator of auxin and cytokinin signalling that regulates root cell proliferation. Here, we report that ectopic expression of WOX 11 gene driven by the promoter of Os HAK 16 encoding a low‐K‐enhanced K transporter led to an extensive root system and adventitious roots and more effective tiller numbers in rice. The WOX 11 ‐regulated root and shoot phenotypes in the Os HAK 16p: WOX 11 transgenic lines were supported by K‐deficiency‐enhanced expression of several RR genes encoding type‐A cytokinin‐responsive regulators, PIN genes encoding auxin transporters and Aux / IAA genes. In comparison with WT , the transgenic lines showed increases in root biomass, root activity and K concentrations in the whole plants, and higher soluble sugar concentrations in roots particularly under low K supply condition. The improvement of sugar partitioning to the roots by the expression of Os HAK 16p: WOX 11 was further indicated by increasing the expression of Os SUT 1 and Os SUT 4 genes in leaf blades and several Os MST s genes in roots. Expression of Os HAK 16p: WOX 11 in the rice grown in moderate K‐deficient soil increased total K uptake by 72% and grain yield by 24%–32%. The results suggest that enlarging root growth and development by the expression of WOX 11 in roots could provide a useful option for increasing K acquisition efficiency and cereal crop productivity in low K soil.