Signaling Pathway
Biosynthesis Pathway
There are no current examples of pathogens targeting this pathway.
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AvrPtoB
AvrPtoB is a type III effector from Pseudomonas syringae strains. de Torres-Zabala et al., 2007 has shown that expression of avrPtoB leads to increased abscisic acid biosynthesis through activation of the NCED3 enzyme and decreased defense gene expression upon bacterial inoculation.
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ABA biosynthetic pathway: The synthesis of ABA being in the plastid and involves the carotenoid zeaxanthin being converted to trans-violaxanthin by the enzyme ZEP/ABA1. The conversion from all-trans-violaxanthin to 9-cis-violaxanthin by a currently unknown enzymatic reaction. Following this conversion, NCED cleaves 9-cis-violaxanthin into xanthoxin, which is considered to be the rate limiting step of this reaction. In the cytosol, xanthoxin is to abscisic aldehyde by SDR/ABA2 and then oxidized to ABA by AAO. Lastly, the molybdenum cofactor is added to ABA by MOCO/ABA3. Arrows indicate positive interaction; blunt-end indicates negative interaction (inhibition).
ABA signaling pathway: ABA signaling starts with ABA being perceived by a PYR/PYL/RCAR receptor protein complex. When ABA is absent the PYR/PYL/RCR proteins are dimers, therefore when ABA is recognized the dimers disassociate. This disassociation leads to conformational changes on the PYR/PYL/RCAR proteins that allows for the formation of a binding site for PP2Cs. The binding of PP2Cs to the PYR/PYL/RCAR complex is followed by a release of the PP2C targets SnRK2s. This release allows the SnRK2s to translocate to the nucleus and phosphorylate the AREB/ABF class bZIP transcription factors that lead to activation of ABA-regulated genes. Arrows indicate positive interaction; blunt-end indicates negative interaction (inhibition).
