Maize Transcription Factor ZmARF4 Confers Phosphorus Tolerance by Promoting Root Morphological Development

Abstract

Plant growth and development are closely related to phosphate (Pi) and auxin. However, data regarding auxin response factors (ARFs) and their response to phosphate in maize are limited. Here, we isolated <i>ZmARF4</i> in maize and dissected its biological function response to Pi stress. Overexpression of <i>ZmARF4</i> in Arabidopsis confers tolerance of Pi deficiency with better root morphology than wild-type. Overexpressed <i>ZmARF4</i> can partially restore the absence of lateral roots in mutant <i>arf7 arf19</i>. The <i>ZmARF4</i> overexpression promoted Pi remobilization and up-regulated <i>AtRNS1</i>, under Pi limitation while it down-regulated the expression of the anthocyanin biosynthesis genes <i>AtDFR</i> and <i>AtANS</i>. A continuous detection revealed higher activity of promoter in the Pi-tolerant maize P178 line than in the sensitive 9782 line under low-Pi conditions. Meanwhile, GUS activity was specifically detected in new leaves and the stele of roots in transgenic offspring. ZmARF4 was localized to the nucleus and cytoplasm of the mesophyll protoplast and interacted with ZmILL4 and ZmChc5, which mediate lateral root initiation and defense response, respectively. <i>ZmARF4</i> overexpression also conferred salinity and osmotic stress tolerance in Arabidopsis. Overall, our findings suggest that <i>ZmARF4</i>, a pleiotropic gene, modulates multiple stress signaling pathways, and thus, could be a candidate gene for engineering plants with multiple stress adaptation.