Plant Cell Signaling: SUMO Is under the Influence of Steroids and Salt

Grégory Vert (1)

1 Signalisation Cellulaire et Ubiquitination

How do plants reduce growth when facing high salinity ? A new study provides insight into how salt stress impinges on the plant steroid hormone signaling pathway to dampen plant growth. Plants are growing in a constantly changing environment and, unlike most animals, cannot run away from adverse conditions. Instead, plants adjust their growth and development using an intricate network of internal signals to ensure completion of their life cycle. Among these, brassinosteroids (BRs), the polyhydroxylated steroid hormones of plants, have been the focus a lot of attention during the past two decades. The main actors driving the perception and signal transduction of BRs in plant cells have now been identified in the model plant Arabidopsis, mostly through intensive genetic and biochemical approaches. A complex cascade of phospho/dephosphorylation events conveys the BR signal from the cell surface to the nucleus where it culminates in the regulation of gene expression by the BRASSINAZOLE RESISTANT (BZR) family of transcription factors [1]. BZR proteins are absolutely essential to BR signaling and more generally to plant growth and development [2]. Their precise regulation in time and space is therefore central and at the node of many pathways ultimately impacting on plant growth. The best characterized regulatory mechanism targeting BZR proteins is a BR-regulated phospho/dephosphorylation coupled to a ubiquitin-mediated degradation by the 26S proteasome that has been brought to light with BZR1 and BZR2, the founding members of the BZR family. In the resting state, plant cells phosphorylate BZRs using the GSK3/SHAGGY kinase BIN2 [1]. This results in the cytosolic localization and destabilization of BZRs, thus shutting down BR genomic responses. When plant cells perceive BRs, BIN2 is inactivated and degraded [3, 4], allowing the dephosphorylation of BZRs by PP2A phosphatases [5]. Dephosphorylated BZRs in turn accumulate in the nucleus where they bind to target promoters to fire BR genomic responses [1]. Recently, additional BR-dependent and-independent mechanisms directly controlling the activity of BZR proteins

Domaines: Biologie végétale; Biochimie, Biologie Moléculaire; Biologie cellulaire

Grégory Vert. Plant Cell Signaling: SUMO Is under the Influence of Steroids and Salt. Current Biology - CB, 2020, 30 (8), pp.R342-R344. ⟨10.1016/j.cub.2020.02.007⟩. ⟨hal-03003448⟩