OsRMC, a negative regulator of salt stress response in rice, is regulated by two AP2/ERF transcription factors

Abstract

High salinity causes remarkable losses in rice productivity worldwide mainly because it inhibits growth and reduces grain yield. To cope with environmental changes, plants evolved several adaptive mechanisms, which involve the regulation of many stressresponsive genes. Among these, we have chosen OsRMC to study its transcriptional regulation in rice seedlings subjected to high salinity. Its transcription was highly induced by salt treatment and showed a stress-dose-dependent pattern. OsRMC encodes a receptor-like kinase described as a negative regulator of salt stress responses in rice. To investigate how OsRMC is regulated in response to high salinity, a salt-induced rice cDNA expression library was constructed and subsequently screened using the yeast one-hybrid system and the OsRMC promoter as bait. Thereby, two transcription factors (TFs), OsEREBP1 and OsEREBP2, belonging to the AP2/ERF family were identified. Both TFs were shown to bind to the same GCC-like DNA motif in OsRMC promoter and to negatively regulate its gene expression. The identified TFs were characterized regarding their gene expression under different abiotic stress conditions. This study revealed that OsEREBP1 transcript level is not significantly affected by salt, ABA or severe cold (5 °C) and is only slightly regulated by drought and moderate cold. On the other hand, the OsEREBP2 transcript level increased after cold, ABA, drought and high salinity treatments, indicating that OsEREBP2 may play a central role mediating the response to different abiotic stresses. Gene expression analysis in rice varieties with contrasting salt tolerance further suggests that OsEREBP2 is involved in salt stress response in rice.

The rice E3 ubiquitin ligase OsHOS1 modulates the expression of OsRMC, a gene involved in root mechano-sensing, through the interaction with two ERF transcription factors

“…OsRMC promoter (Serra et al, 2013). OsRMC, in turn, had already been reported as being involved in rice root curling (Jiang et al, 2007).…”

“…We have previously identified two TFs, OsEREBP1 and OsEREBP2, as binding to the OsRMC promoter region (Serra et al, 2013). Since the down-regulation of OsHOS1 in the transgenic line is up-regulating OsRMC gene expression, we hypothesized that altered OsEREBP1 and OsEREBP2 gene expression could contribute to the higher gene expression levels of OsRMC.…”

“…Here, we propose that the rice root response to mechanical stimuli is modulated by the proteasome. We show that a rice REALLY INTERESTING NEW GENE (RING)-type E3-ubiquitin ligase, HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 (OsHOS1), previously reported as the ortholog of Arabidopsis HOS1 (Ishitani et al, 1998;Lee et al, 2001), targets the two ERF proteins involved in OsRMC transcriptional regulation (Serra et al, 2013) for degradation through the proteasome. Moreover, we demonstrate that the rice root curling phenotype depends on a mechanical barrier and is modulated by JA.…”

“…Knockdown lines showed enhanced JA-sensitive response and increased root curling, suggesting that OsRMC may be involved in the JA-mediated rice root curling response. OsRMC was also implicated in rice abiotic stress responses (Zhang et al, 2009;Serra et al, 2013). Enhanced tolerance to high salinity was described in knockdown lines for this gene (Zhang et al, 2009).…”

“…Enhanced tolerance to high salinity was described in knockdown lines for this gene (Zhang et al, 2009). In addition, two ETHYLENE-RESPONSE FACTOR (ERF) transcription factors (TFs) with a putative role in rice abiotic stress responses were shown to bind the promoter of OsRMC gene (Serra et al, 2013).…”