Low molecular weight protein phosphatase APH mediates tyrosine dephosphorylation and ABA response in Arabidopsis.

Low molecular weight protein tyrosine phosphatase(LWM-PTP),also known as acid phosphatase,is a highly conserved tyrosine phosphatase in living organisms.However,the function of LWM-PTP homolog has not been reported yet in plants.Here,we revealed a homolog of acid phosphatase,APH,in Arabidopsis plants,is a functional protein tyrosine phosphatase.The aph mutants are hyposensitive to ABA in post-germination growth.We performed an anti-phosphotyrosine antibody-based quantitative phosphoproteomics in wild-type and aph mutant and identified hundreds of putative targets of APH,including multiple splicing factors and other transcriptional regulators.Consistently,RNA-seq analysis revealed that the expression of ABA-highly-responsive genes is suppressed in aph mutants.Thus,APH regulates the ABA-responsive gene expressions by regulating the tyrosine phosphorylation of multiple splicing factors and other post-transcriptional regulators.We also revealed that Tyr383 in RAF9,a member of B2 and B3 RAF kinases that phosphorylate and activate SnRK2s in the ABA signaling pathway,is a direct target site of APH.Phosphorylation of Tyr383 is essential for RAF9 activity.Our results uncovered a crucial function of APH in ABA-induced tyrosine phosphorylation in Arabidopsis.