SUMO E3 Ligases GmSIZ1a and GmSIZ1b regulate vegetative growth in soybean

Abstract

SIZ1 is a small ubiquitin‐related modifier (SUMO) E3 ligase that mediates post‐translational SUMO modification of target proteins and thereby regulates developmental processes and hormonal and environmental stress responses in Arabidopsis. However, the role of SUMO E3 ligases in crop plants is largely unknown. Here, we identified and characterized two Glycine max (soybean) SUMO E3 ligases, GmSIZ1a and GmSIZ1b. Expression of GmSIZ1a and GmSIZ1b was induced in response to salicylic acid (SA), heat, and dehydration treatment, but not in response to cold, abscisic acid (ABA), and NaCl treatment. Although GmSIZ1a was expressed at higher levels than GmSIZ1b, both genes encoded proteins with SUMO E3 ligase activity in vivo. Heterologous expression of GmSIZ1a or GmSIZ1b rescued the mutant phenotype of Arabidopsis siz1‐2, including dwarfism, constitutively activated expression of pathogen‐related genes, and ABA‐sensitive seed germination. Simultaneous downregulation of GmSIZ1a and GmSIZ1b (GmSIZ1a/b) using RNA interference (RNAi)‐mediated gene silencing decreased heat shock‐induced SUMO conjugation in soybean. Moreover, GmSIZ1RNAi plants exhibited reduced plant height and leaf size. However, unlike Arabidopsis siz1‐2 mutant plants, flowering time and SA levels were not significantly altered in GmSIZ1RNAi plants. Taken together, our results indicate that GmSIZ1a and GmSIZ1b mediate SUMO modification and positively regulate vegetative growth in soybean.

Post‐translational modifications of Arabidopsis E3 SUMO ligase AtSIZ1 are controlled by environmental conditions

“…Small ubiquitin‐related modifier conjugation was lower in siz1 mutants than in wild‐type Arabidopsis plants, even under heat stress . Conversely, heat‐induced sumoylation of target proteins was observed in several previous studies . In addition, rice E3 SUMO ligases OsSIZ1 and OsSIZ2 were involved in sumoylation of target proteins under heat stress , and transgenic Arabidopsis overexpressing tomato E3 SUMO ligase SISIZ1 also accumulated SUMO conjugates in response to heat stress .…”

“…Numerous proteins are conjugated to SUMO in response to heat stress, suggesting that sumoylation contributes to heat tolerance . Here, AtSIZ1 was polyubiquitinated rather than sumoylated under heat stress conditions (Fig.…”

“…Previous research showed that numerous proteins were modified by SUMO under conditions of heat stress . However, it is unclear whether E3 SUMO ligase is itself regulated by sumoylation or other protein modifications in response to stresses such as heat.…”

“…Cold, heat, and drought stresses stimulate the conjugation of SUMO to a range of target proteins . This suggested that the stability and activity of E3 SUMO ligase might also be post‐translationally modulated by stress.…”

Characterization of transcription activation domain of EcaICE1 and its interaction with EcaSIZ1 in Eucalyptus camaldulensis

“…Studies in A. thaliana have shown that the SUMOylation pathway is mainly mediated by the SUMO E3 ligase SIZ1. Currently, SIZ1 genes have been isolated from plants such as rice (PARK et al 2010), Dendrobium nobile (Liu et al 2015), apple (Zhang et al 2016), soybean (Cai et al 2017) and tomato (Zhang et al 2017), but no study on cloning the gene SIZ1 and its interaction with ICE1 in forest trees. The coding sequence of EcaSIZ1 , which was isolated in this study, is similar to the cloned SIZ1 protein in the above plants, and also has similar protein secondary domains such as MIZ1/SP zinc finger domain, SAP domain, PINIT domain, SXS domain and PHD domain.…”