Involvement of low molecular weight tyrosine acid phosphatase in abscisic acid signaling in Arabidopsis

Low molecular weight protein tyrosine phosphatase (LWM-PTP) is highly conserved tyrosine phosphatase from plants to animals. The function and putative targets of plant LWM-PTP homolog is not reported yet. Here, we revealed that Arabidopsis LWM-PTP homolog APH is a functional tyrosine phosphatase. APH participates in ABA signaling and regulates the ABA-responsive genes by regulates the tyrosine phosphorylation of multiple splicing factors and other transcriptional regulators. APH may also target RAF9, a member of B2 and B3 RAF kinases that activates SnRK2s, the key components in ABA-receptor coupled core signaling pathway. We preformed genetic analysis and found the aph mutants are hyposensitive to ABA in post-germination growth. We also performed an anti-phosphotyrosine antibody-based phosphoproteomics and studied the global change of phosphotyrosine in response to the ABA and APH. Hundreds of proteins, include SR45 and RAF9, are identified putative targets of APH. Consistent with it, aph mutants showed an ABA hyposensitive phenotype and altered expression of ABA-highly-responsive genes. Our results reveal a crucial function of APH in regulating tyrosine phosphorylation and ABA signaling in model plant Arabidopsis.