PDK1 has a pleiotropic PINOID-independent role in Arabidopsis development

The 3-Phosphoinositide-Dependent Protein Kinase 1 (PDK1) is a conserved and important master regulator of AGC kinases in eukaryotic organisms. loss-of-function causes a lethal phenotype in animals and yeast. In contrast, only very mild phenotypic defects have been reported for the loss-of-function mutant of the model plant (Arabidopsis). The Arabidopsis genome contains two genes, hereafter called Here we show that the previously reported Arabidopsis T-DNA insertion alleles are not true loss-of-function mutants. By using CRISPR/Cas9 technology, we created true loss-of-function alleles, and double mutants carrying these alleles showed multiple growth and development defect, including fused cotyledons, a short primary root, dwarf stature, late flowering, and reduced seed production caused by defects in male fertility. Surprisingly, mutants did not phenocopy mutants, and together with the observations that overexpression does not phenocopy the effect of overexpression, and that loss-of-function does not change PID subcellular localization, we conclude that PDK1 is not essential for PID membrane localization or functionality . Nonetheless, most phenotypes could be correlated with impaired auxin transport. is highly expressed in vascular tissues and YFP:PDK1 is relatively abundant at the basal/rootward side of root stele cells, where it colocalizes with PIN auxin efflux carriers, and the AGC1 kinases PAX and D6PK/D6PKLs. Our genetic and phenotypic analysis suggests that PDK1 is likely to control auxin transport as master regulator of these AGC1 kinases in Arabidopsis.