The ETHYLENE RESPONSE FACTORs ERF6 and ERF11 Antagonistically Regulate Mannitol-Induced Growth Inhibition in Arabidopsis

Abstract

Leaf growth is a tightly regulated and complex process, which responds in a dynamic manner to changing environmental conditions, but the mechanisms that reduce growth under adverse conditions are rather poorly understood. We previously identified a growth inhibitory pathway regulating leaf growth upon exposure to a low concentration of mannitol and characterized the ETHYLENE RESPONSE FACTOR (ERF)/APETALA2 transcription factor ERF6 as a central activator of both leaf growth inhibition and induction of stress tolerance genes. Here, we describe the role of the transcriptional repressor ERF11 in relation to the ERF6-mediated stress response in Arabidopsis (Arabidopsis thaliana). Using inducible overexpression lines, we show that ERF6 induces the expression of ERF11. ERF11 in turn molecularly counteracts the action of ERF6 and represses at least some of the ERF6-induced genes by directly competing for the target gene promoters. As a phenotypical consequence of the ERF6-ERF11 antagonism, the extreme dwarfism caused by ERF6 overexpression is suppressed by overexpression of ERF11.Together, our data demonstrate that dynamic mechanisms exist to fine-tune the stress response and that ERF11 counteracts ERF6 to maintain a balance between plant growth and stress defense.Plants are constantly challenged to survive and maintain growth in changing environments. In natural environments, as well as in laboratories, growth conditions are rarely optimal, generating a weak but continuous stress. In such suboptimal conditions, the equilibrium between sustained plant growth and activation of stress defense mechanisms is defied and needs to be continuously rebalanced and fine-tuned (Claeys and Inzé, 2013).To unravel these growth-and defense-related mechanisms in Arabidopsis (Arabidopsis thaliana), researchers commonly use in vitro setups in which different growth inhibitory compounds are added to the growth medium (Verslues et al., 2006;Lawlor, 2013;Claeys et al., 2014). Mannitol, for example, is a frequently applied compound to induce mild stress because it results in both inhibition of leaf growth and activation of stress-responsive genes (Kreps et al., 2002;Skirycz et al., 2010Skirycz et al., , 2011Dubois et al., 2013;Claeys et al., 2014;Trontin et al., 2014). Two putative receptorlike kinases, ENHANCED GROWTH ON MANNITOL1 (EGM1) and EGM2, are presumably involved in the detection of mannitol and further downstream activation of the growth and tolerance responses (Trontin et al., 2014). Previously, we have shown that mannitolinduced responses are specific to the different stages of Arabidopsis leaf development (Skirycz et al., 2010). In very young Arabidopsis leaves, in which cells are not yet expanding but still actively dividing, exposure to mannitol triggers the accumulation of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the transcriptional induction of ethylene-related genes. Interestingly, these responses are extremely fast, with several ETHYLENE RESPONSE FACTORs (ERFs; ERF1, ERF2, ERF5, ERF6, and ERF11...

From network to phenotype: the dynamic wiring of an Arabidopsis transcriptional network induced by osmotic stress

“…However, when we examined growth in more detail in this study, we could observe that the younger leaves of rap2.6L had a reduced size, possibly through decreased cell division. The overexpression of ERF11 caused a decreased rosette size in this and a previous study (Dubois et al , 2015), suggesting that ERF11 is a negative regulator of growth, whereas another study reported that the overexpression of ERF11 resulted in the promotion of internode elongation (Zhou et al , 2016). Even though a contrasting phenotype was observed, a link between ERF11 and the GA2‐OX/DELLA pathway was established.…”

“…We could identify five growth repressors (ERF6, ERF8, ERF9, ERF11, and ERF98) and five growth enhancers (ERF2, ERF59, RAP2.6L, STZ, and WRKY6) (Table EV2). Leaf growth under control conditions has previously been quantified for mutant lines of ERF2, ERF5, ERF6, ERF8, ERF11, RAP2.6L, and WRKY15 (Vanderauwera et al , 2012; Dubois et al , 2013, 2015, 2017; Zhou et al , 2016). RAP2.6L has, for example, been shown to play a role in the regulation of the division of pith cells (Asahina et al , 2011), but no clear growth phenotypes have previously been observed in rap2.6L mutants or RAP2.6L overexpression lines (Krishnaswamy et al , 2011; Liu et al , 2012).…”

“…Per leaf, approximately 100 abaxial epidermal cells were drawn with a DMLB microscope (Leica) fitted with a drawing tube and a differential interference contrast objective. Pictures of the cell drawings were used to measure the average pavement cell area and number with ImageJ as described before (Dubois et al , 2015). …”

“…Because of the resulting lower levels of gibberellin, DELLA proteins are stabilized, which ensures that cells permanently exit the cell division phase and are pushed to cell differentiation (Claeys et al , 2012). The transcriptional repressor ERF11 also has been characterized and could counteract the effect of ERF6 both on molecular and phenotypic level (Dubois et al , 2015). …”

Leaf Growth Response to Mild Drought: Natural Variation in Arabidopsis Sheds Light on Trait Architecture

“…This selection resulted in eight clusters that were enriched for genes involved in drought/osmotic stress responses, cell wall modifications, or cell cycle (Supplemental Data Set 3 and Supplemental Figure 6). Remarkably, the largest of these clusters (cluster A; Supplemental Data Set 4), with 145 genes, contains the main components of a gene regulatory network that was previously proposed to regulate the osmotic stress response of leaf growth (Dubois et al, 2013(Dubois et al, , 2015, with genes such as ACC-SYNTHASE6 (ACS6), ETHYLENE RESPONSE FACTOR6 (ERF6), ERF11, MAP KINASE3 (MPK3), WRKY DNA BINDING PROTEIN 33 (WRKY33), and SALT TOLERANCE ZINC FINGER (STZ). Furthermore, the cluster contains 53 jasmonic acid (JA)-related genes (Supplemental Data Set 4), including the main JA biosynthesis and primary response genes such as JASMONATE INSENSITIVE1 (JAI1/JIN1/MYC2) and multiple JASMONATE ZIM DOMAIN (JAZ) protein-encoding genes (Dombrecht et al, 2007;Pauwels and Goossens, 2011).…”