Coordinated PIN7 and AUX1 responses to arsenite-restrained root growth in Arabidopsis

Arsenite (As III ), regarded as a hazard to human health and food safety, restrains root growth. This event has received little attention, and the mechanism underlying how As III affects auxin dynamics to repress root growth remains unknown. Here, our results have suggested that As III -inhibited root growth possibly involved an elevated auxin level in roots, as supported in multiple experiments such as (1) transgenic DII-VENUS and DR5rev::GFP ; (2) IAA determination by enzyme-linked immunosorbent assay; (3) phenotype analysis of taa1 (defective in auxin biosynthesis) mutant; and (4) the external application of 1-naphthylphthalamic acid (NPA) to manipulate auxin transport. This consequence could be explained through up-regulated transcriptional levels of auxin biosynthesis-related genes in whole plants. Phenotypes of auxin transport-related carriers have displayed that loss of PIN7 and AUX1, but not PIN1/2/3 transporters, ameliorated the extent of As III -induced root growth inhibition. Moreover, As III specifically enhanced the abundance of PM-localized PIN7 and AUX1 involved in transcriptional but not post-transcriptional regulation. A real-time in vitro observation of PM-localized PIN2 using the transgenic pPIN2::PIN2-Dendra2 line has revealed that As III did not influence the endocytosis of PM-localized PIN2 carriers in root apices. Overall, our results propose that As III stress-elevated auxin level in the root apex possibly involves up-regulation transcriptional levels of auxin biosynthesis- and auxin transport-related genes but does not target PIN2 dynamics, finally, leading to auxin accumulation in root apices and root growth inhibition. • As III stress caused an elevated auxin level in root apices. • As III stress up-regulated auxin biosynthesis-related genes and PIN7 and AUX1 . • As III stress did not impede PIN2 endocytosis.