A signaling pathway complementary to the core known ABA signaling conected to JA signaling

What is it about?

The phytohormone abscisic acid (ABA) is produced under abiotic stress conditions and functions in several plant developmental stages regulating gene expression. The ABA signaling core involves three protein families: the PYR/PYL/RCAR receptors, the clade A of PP2C phosphatases and SnRK2 kinases. Likewise, the phytohormone jasmonic acid (JA) regulates some responses to abiotic stresses but mainly to biotic stresses, with the transcription factor MYC2 as a hub for JA signaling. Although crosstalk between ABA and JA has been shown, the molecular entities that mediate this interaction have yet to be identified. This manuscript reports key findings in the ABA and JA research fields as follows: 1.- Starting from an interaction screening platform, we report a mechanistic link between ABA and JA signaling through a direct interaction of the ABA receptor PYL6 with the transcription factor MYC2. 2.- The interaction between PYL6 and MYC2 modifies the transcriptional activity of MYC2, providing evidence for a direct new mechanism for ABA-induced gene regulation different from the classical ABA signaling core. 3.- We also provide a previously unknown working model for how MYC2 acts as a positive regulator of ABA signaling, which represents a novel direct ABA signaling mechanism different from the core elements known so far.

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Why is it important?

This paper shows how a protein receptor (PYL6) can change the activity of a transcription factor (MYC2). PYL6 sense environmental cues depending on the concentration of the plant hormone ABA. Therefore, we describe a direct signal transduction pathway of gene regulation based on the environment. Modifying this gene regulation pathway might allow us to create plants more tolerant to abiotic stresses. PYL6 is a hormone receptor, not a protein related to transcription. If not the first one, it is one of the few papers that report a direct modulation of the transcriptional activity upon interaction with a protein not related to transcription. (I’d like to know if others have reported something similar before, if not the first one). The experiments suggest that the affinity of MYC2 for different promoters is changed upon interaction with the hormone receptor. In addition, we provide a mechanistic link between the plant hormones ABA and JA through a direct interaction of the ABA receptor PYL6 with the transcription factor MYC2.

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