SUMO Aids Rapid Regulation of Hormone Responses

Srivastava et al. identify a mechanism for rapid regulation of jasmonic acid signaling. Plant Cell  https://doi.org/10.1105/tpc.18.00036

Background: The sessile nature of plants dictates that growth must be integrated with changes in the natural environment. Modulation of hormone signalling pathways plays a key role in this process. Jasmonic acid (JA) regulates a wide spectrum of plant growth, developmental, and defence responses to pathogen attack. In this context, JA is a major coordinator of both constitutive developmental processes and defence responses activated upon pathogen invasion.

Questions: How can JA responses be modulated rapidly prior to changes in hormone levels?

Findings: In this report, we demonstrate that regardless of intrinsic JA levels, Small Ubiquitin-like Modifier (SUMO)- conjugated JAZ proteins inhibit the JA receptor CORONATINE INSENSITIVE1 (COI1) from mediating nonSUMOylated JAZ degradation. We identify the SUMO interacting motif (SIM) in COI1 and demonstrate that this is vital to SUMO-dependent inhibition of COI1. The SUMO-deconjugating proteases OVERLY TOLERANT TO SALT1 (OTS1) and OTS2 regulate JAZ protein SUMOylation and stability. Necrotroph infection of Arabidopsis thaliana promotes SUMO protease degradation, and this increases JAZ SUMOylation and abundance, which in turn inhibits JA signaling. This study reveals a mechanism for rapidly regulating JA responses, allowing plants to adapt to environmental changes.

Next steps: Recent evidence indicates that DELLA and JAZ proteins directly interact to mediate crosstalk between gibberellic acid and JA. The discovery that both DELLA and JAZ proteins are SUMOylated leads to the possibility that SUMO may provide a new facet to this crosstalk. In the future, identifying the role of SUMO in mediating crosstalk between hormones will likely lead to new avenues for boosting plant tolerance to environmental stress.

Anjil Kumar Srivastava, Beatriz Orosa, Prashant Singh, Ian Cummins, Charlotte Walsh, Cunjin Zhang, Murray Grant, Michael R. Roberts, Ganesh Srinivasan Anand, Elaine Fitches, Ari Sadanandom. (2018). SUMO Suppresses the Activity of the Jasmonic Acid Receptor CORONATINE INSENSITIVE1. Plant Cell 30: 2099-2115; DOI: https://doi.org/10.1105/tpc.18.00036