E2 conjugases UBC1 and UBC2 regulate MYB42‐mediated SOS pathway in response to salt stress in Arabidopsis

Abstract

Summary Histone H2B monoubiquitination (H2Bub1) is recognized as a crucial eukaryotic regulatory mechanism that controls a range of cellular processes during both development and adaptation to environmental changes. In Arabidopsis, the E2 conjugated enzymes UBIQUITIN CARRIER PROTEINs (UBCs) ‐1 and ‐2 mediate ubiquitination of H2B. Here, we elucidated the functions of UBC1 and ‐2 in salt‐stress responses and revealed their downstream target genes. Real‐time quantitative PCR assays showed that UBC1 and ‐2 positively regulated the salt‐induced expression of MYB42 and Mitogen‐Activated Protein Kinase 4 (MPK4). Chromatin immunoprecipitation assays revealed that H2Bub1 was enriched weakly on the chromatin of MYB42 and MPK4 in the ubc1,2 mutant. We further determined that UBC1/2‐mediated H2Bub1 enhanced the level of histone H3 tri‐methylated on K4 (H3K4me3) in the chromatin of MYB42 and MPK4 under salt‐stress conditions. MPK4 interacted with and phosphorylated MYB42. The MPK4‐mediated MYB42 phosphorylation enhanced the MYB42 protein stability and transcriptional activity under salt‐stress conditions. We further showed that MYB42 directly bound to the SALT OVERLY SENSITIVE 2 (SOS2) promoter and mediated the rapid induction of its expression after a salt treatment. Our results indicate that UBC1 and ‐2 positively regulate salt‐stress responses by modulating MYB42‐mediated SOS2 expression.

Protein kinases in plant responses to drought, salt, and cold stress

“…In a positive feedback loop, SOS2 phosphorylates SCaBP8, which enhances the interaction between SOS2 and SCaBP8, resulting in higher plasma membrane Na + /H + exchange activity (Lin et al, 2009). The expression of SOS2 is directly regulated by the MYB domain transcription factor MYB42 under salt stress (Sun et al, 2020) (Figure 2).…”

“…Interestingly, a recent study identified the glucose sensor HEXOKINASE 1 (MdHXK1) in apple ( Malus domestica Borkh. ), where it phosphorylates MdNHX1 and enhances its activity to confer improved salt tolerance (Sun et al, 2018). As most studies on HXK1 are focused on its roles in glucose sensing, the finding that MdHXK1 participates in salt stress indicates that this protein has broader biological roles in plants.…”

Multiple Functions of MYB Transcription Factors in Abiotic Stress Responses

“…Salt treatment can induce the degradation of MYB42. This phosphorylation enhances the stability of MYB42 under salt-stress conditions [ 62 ].…”

GmNAC06, a NAC domain transcription factor enhances salt stress tolerance in soybean

“…cDNA samples of GmNAC06 from the OE and VC hairy roots were used to examine the expression level of 14 salt stress-related genes by qRT-PCR (Table S1). The expression level of 2 salt stress-related genes in the OE, VC and WT Arabidopsis were examined by qRT-PCR (Shkolnik et al 2013;Sun et al 2020). The soybean CYP2 gene and Arabidopsis UBQ3 gene were used as a reference for normalization (Ni et al 2013).…”