Dr. Tzyy-Jen Chiou
Speaker's Institution
Agricultural Biotechnology Research Center, Academia Sinica, Taiwan
4:00 PM
Anatomy/Zoology Building W118
Mixer Time
3:30 PM
Mixer Time
Anatomy/Zoology Building E112
Calendar (ICS) Event
Additional Information

 Phosphorous is an essential plant nutrient that is mainly acquired as a form of inorganic phosphate (Pi) from soil. Recently, we revealed a mechanism by which plants control Pi homeostasis to adapt to external Pi availability. This mechanism involves interplay between two Pi starvation-induced microRNAs, miR399 and miR827. In Arabidopsis, miR399 and miR827 direct the cleavage of PHO2 and NLA transcripts, respectively. PHO2 encodes a ubiquitin E2 conjugase associated with endomembranes while NLA encodes a RING-type ubiquitin E3 ligase localized in plasma membranes. Loss-of-function of PHO2 or NLA results in excess Pi accumulation. We found that PHO2 modulates the activity of xylem loading of Pi via mediating the protein degradation of PHO1. Furthermore, both PHO2 and NLA regulate the degradation of PHT1 Pi transporters. Analyses of nla pho2 mutants suggest that NLA and PHO2 function independently but cooperatively to control Pi acquisition. PHO2 regulates the abundance of PHT1s in the secretory pathway destined for the plasma membranes whereas NLA controls the abundance of PHT1s in the plasma membranes by endocytosis. Upon Pi deprivation, upregulation of miR399 and miR827 suppresses the expression of PHO2 and NLA, respectively, thereby alleviating the negative regulation of PHO1 and PHT1s and reinforcing Pi translocation and uptake activities. Intriguingly, miR399 can move systemically from shoots to roots, serving as a signal to balance the Pi demand in shoots and Pi supply in roots. This study demonstrates the regulation of Pi transport through integration of miRNA-mediated posttranscriptional and ubiquitin-mediated posttranslational pathways.