An ABA-increased interaction of the PYL6 ABA receptor with MYC2 Transcription Factor: A putative link of ABA and JA signaling.

Fernando Aleman,Julian I Schroeder,Melissa Lee,Toshinori Kinoshita,Alice Y Kim,Zixing Li,Yohei Takahashi,Joseph R Ecker,Junshi Yazaki

doi:10.1038/srep28941

Abstract

Abscisic acid (ABA) is a plant hormone that mediates abiotic stress tolerance and regulates growth and development. ABA binds to members of the PYL/RCAR ABA receptor family that initiate signal transduction inhibiting type 2C protein phosphatases. Although crosstalk between ABA and the hormone Jasmonic Acid (JA) has been shown, the molecular entities that mediate this interaction have yet to be fully elucidated. We report a link between ABA and JA signaling through a direct interaction of the ABA receptor PYL6 (RCAR9) with the basic helix-loop-helix transcription factor MYC2. PYL6 and MYC2 interact in yeast two hybrid assays and the interaction is enhanced in the presence of ABA. PYL6 and MYC2 interact in planta based on bimolecular fluorescence complementation and co-immunoprecipitation of the proteins. Furthermore, PYL6 was able to modify transcription driven by MYC2 using JAZ6 and JAZ8 DNA promoter elements in yeast one hybrid assays. Finally, pyl6 T-DNA mutant plants show an increased sensitivity to the addition of JA along with ABA in cotyledon expansion experiments. Overall, the present study identifies a direct mechanism for transcriptional modulation mediated by an ABA receptor different from the core ABA signaling pathway, and a putative mechanistic link connecting ABA and JA signaling pathways.

Highlights

Environmental stresses affect plant growth and crop yield worldwide, and threaten food supply for a growing population
We performed a study of protein-protein interactions using a high-density protein array, where 12,000 Arabidopsis proteins were synthetized on glass slides and tested for interactions with 38 Transcription Factors (TF) proteins that function in diverse plant hormone regulatory pathways (Yazaki et al, Mapping transcription factor interactome networks using HaloTag protein arrays, PNAS in press)
To test for the specificity of this interaction in yeast, we investigated the closest homologue of PYL6, PYL5, and the closest homologue of MYC2, MYC3, and did not observe PYL5 interaction with MYC2 or MYC3, nor PYL6 interaction with MYC3 (Fig. 1A)

Summary

Introduction

Environmental stresses affect plant growth and crop yield worldwide, and threaten food supply for a growing population. The PYL/RCAR ABA receptor family comprises 14 members in the reference plant Arabidopsis thaliana, and they have been subdivided into 3 subgroups based on sequence similarity[6,7]. The interaction observed between the ABA receptors and PP2Cs in yeast, in the absence of ABA, does not always result in the inhibition of PP2C protein phosphatase activity in vitro[6,7,12,19,20,21]. Similar to other ‘monomeric’ ABA receptors, PYL6/RCAR9 displays high-affinity for ABA binding[11]. This subgroup of ABA receptors is up- or down-regulated at the mRNA level by JA28. The mechanisms underlying the interaction of PYR/RCAR receptors with jasmonate signaling remain unknown

Methods

Results

Conclusion