Pizzio GA, Rodriguez L, Antoni R, Gonzalez-Guzman M, Yunta C, Merilo E, Kollist H, Albert A, Rodriguez PL

Since ABA is recognized as the critical hormonal regulator of plant stress physiology, elucidating its signaling pathway has raised promise for application in agriculture, for instance through genetic engineering of ABA receptors. PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKE (PYL)/ REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR) ABA receptors interact with high affinity and inhibit ...

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clade A phosphatases type-2C (PP2Cs) in an ABA-dependent manner. We generated an allele library composed of 10000 mutant clones of Arabidopsis thaliana PYL4 and selected mutations that promoted ABA-independent interaction with PP2CA/ABA-HYPERSENSITIVE3 (AHG3). In vitro protein-protein interaction assays and size exclusion chromatography confirmed that PYL4A194T was able to form stable complexes with PP2CA in the absence of ABA, in contrast to PYL4. This interaction did not lead to significant inhibition of PP2CA in the absence of ABA; however, it improved ABA-dependent inhibition of PP2CA. As a result, 35S:PYL4A194T plants showed enhanced sensitivity to ABA-mediated inhibition of germination and seedling establishment compared to 35S:PYL4 plants. Additionally, at basal endogenous ABA levels, whole rosette gas-exchange measurements revealed reduced stomatal conductance (Gst) and enhanced water use efficiency (WUE) compared to non-transformed or 35S:PYL4 plants, and partial up-regulation of two ABA-responsive genes. Finally, 35S:PYL4A194T plants showed enhanced drought and dehydration resistance compared to non-transformed or 35S:PYL4 plants. Thus, we describe a novel approach to enhance plant drought resistance through allele library generation and engineering of a PYL4 mutation that enhances interaction with PP2CA.

Date: Jul. 17, 2013

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