An ethylene response factor OsWR1 responsive to drought stress transcriptionally activates wax synthesis related genes and increases wax production in rice

Abstract

Increasing evidence has revealed the major enzymes-involved in Arabidopsis and maize wax/cutin synthesis; however, there is limited information about the genes-associated with wax/cutin synthesis in rice. Here we report the characterization of an ethylene response factor gene in rice. This rice wax synthesis regulatory gene 1 (OsWR1) is a homolog of Arabidopsis wax/cutin synthesis regulatory gene WIN1/SHN1. Transcript analysis showed that OsWR1 is induced by drought, abscisic acid and salt, and is predominantly expressed in leaves. Functional analyses indicated that overexpressing OsWR1 (Ox-WR1) improved while RNA interference OsWR1 rice (RI-WR1) decreased drought tolerance, consistent with water loss and cuticular permeability, suggesting that OsWR1-triggered drought response might be associated with cuticular characteristics. In addition, OsWR1 activated the expression of the genes-related to oxidative stress response and membrane stability. Gas chromatograph-mass spectrometry analysis further showed that OsWR1 modulated the wax synthesis through alteration of long chain fatty acids and alkanes, evidencing the regulation of OsWR1 in wax synthesis. Detection with real-time PCR amplification indicated that Ox-WR1 enhanced while RI-WR1 decreased the expression of wax/cutin synthesis related genes. Furthermore, OsWR1 physically interacted with the DRE and GCC box in the promoters of wax related genes OsLACS2 and OsFAE1'-L, indicating that OsWR1 at least directly modulates the expression of these genes. Thus our results indicate that OsWR1 is a positive regulator of wax synthesis related genes in rice, and this regulation, distinct from its homology regulator of WIN1/SHN1 in cutin synthesis, subsequently contributes to reduced water loss and enhanced drought tolerance.

Putative megaenzyme DWA1 plays essential roles in drought resistance by regulating stress-induced wax deposition in rice

“…It has been proposed that cuticular alkanes confer greater resistance to water diffusion than VLCFAs (13,19). However, total FAs are the major constituents of cuticular wax in rice (16,23), and we obtained similar results in this study. Under drought stress, total FAs, including VLCFAs and LCFAs, were the major components contributing to the increase in the level of wax seen in the WT rice (Fig.…”

“…Overexpression of SHN1/WIN1 caused elevated wax deposition and drought tolerance but unexpectedly increased cuticle permeability and water loss (22). Modulating the expression of rice SHN1/WIN1 homolog wax synthesis regulator 1 (OsWR1) altered wax production and drought tolerance (23). It is unknown how cuticular wax biosynthesis is regulated under drought stress; however, one recent report has shown that MYB96 regulates some wax-biosynthetic genes in Arabidopsis, suggesting it may be required for droughtinduced cuticular wax biosynthesis (13).…”

Cuticle Biosynthesis in Tomato Leaves Is Developmentally Regulated by Abscisic Acid

“…Previous studies have shown that environmental stresses, such as drought, increase ABA levels, resulting in the increased production of cuticular waxes Seo et al, 2009Seo et al, , 2011Wang et al, 2012). In this study, we conclude that ABA regulation of cuticle formation is an intrinsic aspect of leaf development.…”

“…While the levels of waxes, and in particular alkanes, were reported to increase following ABA application, no such change in the abundance of cutin monomers was observed, suggesting that other factors trigger changes in the cuticle following water stress . Furthermore, the expression levels of numerous wax biosynthesis-related genes are known to respond to ABA treatment Seo et al, 2009Seo et al, , 2011Wang et al, 2012). For example, the expression of ECERIFERUM1 (CER1), which encodes an enzyme that generates alkanes from very-long-chain acyl-CoA (Bernard et al, 2012), is induced by ABA treatments ).…”

EARLY SENESCENCE1 Encodes a SCAR-LIKE PROTEIN2 That Affects Water Loss in Rice

“…For example, the composition, thickness, and microstructure of the cuticular wax affect water permeability and transport (Svenningsson, 1988;Xu et al, 1995;Buschhaus and Jetter, 2012). Rice DROUGHT-INDUCED WAX ACCUMULATION1, GLOSSY1, and WAX SYNTHESIS REGULATORY GENE1 affect drought tolerance by regulating the deposition or biosynthesis of cuticular wax (Islam et al, 2009;Wang et al, 2012;Zhou et al, 2013;Zhu and Xiong, 2013).…”