Arabidopsis miR399-PHO2 and miR827-NLA modules function independently but cooperatively to maintain phosphate homeostasis

Phosphorus is one of the essential plant nutrients acquired as the form of phosphate (Pi) by PHOSPHATE TRANSPORTER1 (PHT1) from rhizosphere. In Arabidopsis, miR399 and miR827, induced by Pi deficiency downregulate PHOSPHATE2 (PHO2) that encodes a endomembrane-localized ubiquitin-conjugating E2 enzyme and NITROGEN LIMITATION ADAPTATION (NLA) that encodes a plasma membrane-associated RING-type ubiquitin-ligating E3 enzyme, respectively. In these two studies, we performed root membrane proteomic analysis and genetic studies and demonstrated that PHO2 and NLA function cooperatively in different cell compartments to mediate the degradation of PHT1 proteins. Our findings reveal that the action of miR399-PHO2 and miR827-NLA modules in two different ubiquitin conjugation cascades independently contributes to the post-translational regulation of PHT1 along the secretory and endocytic pathways in response to Pi availability, which eventually determines the quantity of Pi transporters and the Pi uptake activity at the cell surface. Furthermore, this study provides large database of root membrane proteome for future research.

Co-researchers:T-K Huang, W-Y Lin, C-L Han, S-I Lin, Y-J Chen, Y-C Tsai, Y-R Chen, J-W Chen, P-M Chen, T-Y Liu, Y-S Chen, C-M Sun, and T-J Chiou＊