Functional analysis of select Arabidopsis ABA INSENSITIVE1/2-Like protein phosphatases
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We have utilized a maize protoplast transient gene expression system to investigate the possible roles of several Arabidopsis protein phosphatase type 2C (PP2Cs), which are predicted to be involved in ABA responses by hierarchical clustering meta-analysis of transcriptome profiling datasets and sequence homologies to known PP2C effector ABA INSENSITIVE1. We recombined Cre-lox UPS host acceptor vectors (pCR701-705) containing the maize Ubiquitin promoter and N-terminal epitope tags with pUNI donor vectors containing various full length Arabidopsis PP2C cDNAs. On the basis of my maize protoplast transient expression data that suggested ABA antagonist effects of several overexpressed PP2Cs, I performed a reverse-genetic screen for AP2C9, AP2C12 and AP2C15 T-DNA insertion mutants and found supportive evidence from physiological assays on seed germination and root growth that these PP2Cs may be involved in ABA signaling. I conclude that the utilization of the maize protoplast transient expression system for moderate-throughput functional screening and systems-approach classification of gene activities can contribute to elucidation of plant abscisic acid (ABA) signal transduction pathways when combined with complimentary genetic and physiological approaches.