Ethylene Signaling Negatively Regulates Freezing Tolerance by Repressing Expression of CBF and Type-A ARR Genes in Arabidopsis

Abstract

The phytohormone ethylene regulates multiple aspects of plant growth and development and responses to environmental stress. However, the exact role of ethylene in freezing stress remains unclear. Here, we report that ethylene negatively regulates plant responses to freezing stress in Arabidopsis thaliana. Freezing tolerance was decreased in ethylene overproducer1 and by the application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid but increased by the addition of the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine or the perception antagonist Ag + . Furthermore, ethylene-insensitive mutants, including etr1-1, ein4-1, ein2-5, ein3-1, and ein3 eil1, displayed enhanced freezing tolerance. By contrast, the constitutive ethylene response mutant ctr1-1 and EIN3-overexpressing plants exhibited reduced freezing tolerance. Genetic and biochemical analyses revealed that EIN3 negatively regulates the expression of CBFs and type-A Arabidopsis response regulator5 (ARR5), ARR7, and ARR15 by binding to specific elements in their promoters. Overexpression of these ARR genes enhanced the freezing tolerance of plants. Thus, our study demonstrates that ethylene negatively regulates cold signaling at least partially through the direct transcriptional control of cold-regulated CBFs and type-A ARR genes by EIN3. Our study also provides evidence that type-A ARRs function as key nodes to integrate ethylene and cytokinin signaling in regulation of plant responses to environmental stress.

Opposing control by transcription factors MYB61 and MYB3 Increases Freezing Tolerance by relieving C-repeat Binding Factor suppression

“…Briefly, 5-week-old whole plants grown in a soil:vermiculite (1:2, v/v) mixture with or without cold acclimation were subsequently placed in a freezing chamber (RuMED4001; Shi et al, 2012) that was set to maintain a temperature of 0°C for 1 h. The temperature was then decreased at a rate of 1°C h 21 in the dark. The plants were maintained for 1 h at the designated temperature from 22°C to 29°C and transferred to 4°C overnight, then transferred back to 22°C with light (16-h daylength).…”

“…In addition, OST1, a protein kinase involved in abscisic acid (ABA) signaling, phosphorylates and stabilizes ICE1 and suppresses HOS1-mediated ICE1 degradation, thus positively regulating CBFs (Ding et al, 2015). Finally, ethylene represses AtCBF1 to AtCBF3 expression via EIN3 (Shi et al, 2012).…”

Potential role of salicylic acid in modulating diacylglycerol homeostasis in response to freezing temperatures in Arabidopsis

“…Unlike the signal molecules JAs and ethylene, which show immediate accumulation during cold acclimation in Arabidopsis, the contents of free and conjugated SA increase only after one week of treatment. [24][25][26][27] Our recent work further revealed that the levels of SA were significantly increased upon freezing and during the recovery phase after freezing treatment in the wild-type plants, which elevations were absent in the freezing-tolerant sag101, eds1 and pad4 mutants. 18 These findings demonstrate that SAG101, EDS1-and PAD4-mediated SA signaling may contribute to freezing tolerance through a novel mechanism different from the conventional pathways.…”

“…21 In addition, overexpression of type-A ARABIDOPSIS RESPONSE REGULATORS (ARR) genes, ARR5, ARR7 and ARR15, confers enhanced freezing tolerance in Arabidopsis. 24 A recent investigation further suggests that the transcript and protein levels of ARRs are down-regulated by supplying with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), indicating that the type-A ARRs may be key factors in integrating ethylene and cytokinin pathways in plant responses to cold stresses. 24 Due to the frequent cross-talks between the ethylene and SA pathways, it is necessary to test the effects of SA on the regulation of cold-responsive expression of ARR genes as well as their expression patterns in the freezing-tolerant sag101, eds1 and pad4 mutants.…”

Modelling Plant Hormone Gradients

“…1) the activities of hormones such as auxin, ethylene, cytokinin, abscisic acid, gibberellin and brassinosteroids depend on cellular context and exhibit either synergistic or antagonistic interactions (Garay-Arroyo et al, 2012); 2) cellular patterning in the Arabidopsis root is coordinated via a localized auxin concentration maximum in the root tip, requiring the regulated expression of specific genes (Sabatini et al, 1999); 3) auxin is directionally transported through plant tissues, providing positional and vectorial information during development (Vanneste and Friml, 2009;Adamowski and Friml, 2015); 4) auxin concentration and the associated regulatory and target genes are regulated by diverse interacting hormones and gene expression and therefore cannot change independently of the various crosstalk components in space and time (Garay-Arroyo et al, 2012); 5) other hormone concentrations, such as ethylene and cytokinin concentrations, and expression of the associated regulatory and target genes are also interlinked (e.g. To et al, 2004;Shi et al, 2012); and 6) transport of other hormones, such as cytokinin, from the shoot to the root in the phloem (Bishopp et al, 2011;Schaller et al, 2015) in combination with local biosynthesis, degradation and diffusion, could also be an important factor affecting the interaction of hormones and gene expression in Arabidopsis root development.…”