Chinese Wild-Growing Vitis amurensis ICE1 and ICE2 Encode MYC-Type bHLH Transcription Activators that Regulate Cold Tolerance in Arabidopsis

Abstract

Winter hardiness is an important trait for grapevine breeders and producers, so identification of the regulatory mechanisms involved in cold acclimation is of great potential value. The work presented here involves the identification of two grapevine ICE gene homologs, VaICE1 and VaICE2, from an extremely cold-tolerant accession of Chinese wild-growing Vitis amurnensis, which are phylogenetically related to other plant ICE1 genes. These two structurally different ICE proteins contain previously reported ICE-specific amino acid motifs, the bHLH-ZIP domain and the S-rich motif. Expression analysis revealed that VaICE1 is constitutively expressed but affected by cold stress, unlike VaICE2 that shows not such changed expression as a consequence of cold treatment. Both genes serve as transcription factors, potentiating the transactivation activities in yeasts and the corresponding proteins localized to the nucleus following transient expression in onion epidermal cells. Overexpression of either VaICE1 or VaICE2 in Arabidopsis increase freezing tolerance in nonacclimated plants. Moreover, we show that they result in multiple biochemical changes that were associated with cold acclimation: VaICE1/2-overexpressing plants had evaluated levels of proline, reduced contents of malondialdehyde (MDA) and decreased levels of electrolyte leakage. The expression of downstream cold responsive genes of CBF1, COR15A, and COR47 were significantly induced in Arabidopsis transgenically overexpressing VaICE1 or VaICE2 upon cold stress. VaICE2, but not VaICE1 overexpression induced KIN1 expression under cold-acclimation conditions. Our results suggest that VaICE1 and VaICE2 act as key regulators at an early step in the transcriptional cascade controlling freezing tolerance, and modulate the expression levels of various low-temperature associated genes involved in the C-repeat binding factor (CBF) pathway.

An eggplant SmICE1a gene encoding MYC‐type ICE1‐like transcription factor enhances freezing tolerance in transgenic Arabidopsis thaliana

“…A similar phenomenon occurs in grape: overexpression of VaICE1 or VaICE2 in Arabidopsis could up‐regulate CBF transcript levels under control conditions (Xu et al . ). Further study is required to investigate the relationship between transcription activity of SmICE1a and cold tolerance.…”

Arabidopsis AtbHLH112 regulates the expression of genes involved in abiotic stress tolerance by binding to their E‐box and GCG‐box motifs

“…Two types of enzyme, ProDH and P5CDH, function in the degradation of proline (Cecchini et al, 2011). A previous study has demonstrated that overexpression of bHLH increases the proline content in transgenic Arabidopsis; however, the authors did not investigate whether bHLH regulates the expression of genes related to proline metabolism (Xu et al, 2014). The results of the present study showed that the transcript levels of AtbHLH112 were positively correlated with the expression of both P5CS genes, but negatively correlated with the expression of ProDH and P5CDH under salt and osmotic stress conditions (Fig.…”

The transcription factor ICE1 functions in cold stress response by binding to the promoters of CBF and COR genes

“…These findings support the inference that ICE1 has a function in regulating the expression of CBF and COR genes under cold stress, and that ICE1 and ICE2 together contribute even more to the cold‐induced gene expression and freezing tolerance. In addition, a role of ICE1 homologs in cold stress response has been observed in many plant species such as rice, tomato, Zea mays, Chrysanthemum dichrum , Chinese wild Vitis amurensis, Pyrus ussuriensis, Poncirus trifoliata , and Cucumis sativus (Liu et al 2010; Feng et al 2013; Xu et al 2014; Huang et al 2015a, 2015b; Lu et al 2017; Zhang et al 2017).…”