MicroRNA-mediated surveillance of phosphate transporters on the move.

Phosphate (Pi), which is indispensable for the structural and metabolic needs of plants, is acquired and translocated by Pi transporters. Deciphering the regulatory network of Pi signaling and homeostasis that involves the control of Pi transporters trafficking to, and their activity at, the plasma membrane provides insight into how plants adapt to environmental changes in Pi availability. Here, we review recent studies that revealed the involvement of microRNA399-PHOSPHATE 2 (PHO2) and microR827-NITROGEN LIMITATION ADAPTATION (NLA) modules in mediating the ubiquitination and degradation of PHOSPHATE TRANSPORTER 1 (PHT1) and/or PHOSPHATE 1 (PHO1). These discoveries show that miRNAs are an effective way for plants to monitor the turnover of Pi transporters in the membrane system by modulating the functioning of the membrane-associated ubiquitin machinery.