Tyrosylprotein sulfotransferase suppresses ABA signaling via sulfation of SnRK2.2/2.3/2.6

Phytohormone abscisic acid(ABA)plays vital roles in stress tolerance,while long-term overactivation of ABA signaling suppresses plant growth and development.However,the braking mechanism of ABA responses is not clear.Protein tyrosine sulfation catalyzed by tyrosylprotein sulfotransferase(TPST)is a critical post-translational modification.Through genetic screening,we identified a tpst mutant in Arabidopsis that was hypersensitive to ABA.In-depth analysis revealed that TPST could interact with and sulfate SnRK2.2/2.3/2.6,which accelerated their degradation and weakened the ABA signaling.Taken together,these findings uncovered a novel mechanism of desensitizing ABA responses via protein sulfation.

Abscisic acid signaling negatively regulates nitrate uptake via phosphorylation of NRT1.1 by SnRK2s in Arabidopsis

Nitrogen(N)is a limiting nutrient for plant growth and productivity.The phytohormone abscisic acid(ABA)has been suggested to play a vital role in nitrate uptake in fluctuating N environments.However,the molecular mechanisms underlying the involvement of ABA in N deficiency responses are largely unknown.In this study,we demonstrated that ABA signaling components,particularly the three subclass Ⅲ SUCROSE NON-FERMENTING1(SNF1)-RELATED PROTEIN KINASE 2 S(SnRK2)proteins,function in root foraging and uptake of nitrate under N deficiency in Arabidopsis thaliana.The snrk2.2 snrk2.3 snrk2.6 triple mutant grew a longer primary root and had a higher rate of nitrate influx and accumulation compared with wild-type plants under nitrate deficiency.Strikingly,SnRK2.2/2.3/2.6 proteins interacted with and phosphorylated the nitrate transceptor NITRATE TRANSPORTER1.1(NRT1.1)in vitro and in vivo.The phosphorylation of NRT1.1 by SnRK2 s resulted in a significant decrease of nitrate uptake and impairment of root growth.Moreover,we identified NRT1.1Ser585 as a previously unknown functional site:the phosphomimetic NRT1.1S585 D was impaired in both low-and high-affinity transport activities.Taken together,our findings provide new insight into how plants fine-tune growth via ABA signaling under N deficiency.