Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2006
Publication Date: 3/1/2007
Citation: Xin, Z., Chen, J., Mandaokar, A., Last, R., Browse, J. 2007. Arabidopsis ESK1 encodes a novel regulator of freezing tolerance. Plant Journal. 49:786-799.
Interpretive Summary: Many temperate plants acquire freezing tolerance in response to a period of low nonfreezing temperatures through an adaptive process known as cold acclimation. Cold acclimation is complex and involves multiple pathways. To identify the mechanisms modulating freezing tolerance in higher plants, we have isolated a series of Arabidopsis mutants that are constitutively freezing tolerant in the absence of cold acclimation. Non-acclimated esk1 mutant can withstand freezing at -10ºC while wild-type Arabidopsis can only survive freezing at -5ºC. Using positional cloning strategy, we identified the gene, ESK1, which encodes a novel regulator of freezing tolerance. Genechip analysis revealed that 169 genes were up-regulated and 137 genes were down-regulated for two-fold or more in esk1 mutants. The identification of ESK1 gene offered a new avenue to improve freezing tolerance in plants.
Technical Abstract: Many temperate plants acquire freezing tolerance in response to a period of low nonfreezing temperatures through an adaptive process known as cold acclimation. Cold acclimation is complex and involves multiple changes in gene expression, metabolism, and morphology. Recessive or knockout mutations in ESK1 gene of Arabidopsis activated a constitutive freezing tolerance equivalent to 70% of the freezing tolerance obtainable in fully acclimated wild-type plants. Transcriptome analysis in a missense mutant allele and a knockout mutant allele revealed that 169 genes were up-regulated and 137 genes were down-regulated for two-fold or more in esk1 mutants. The ESK1-mediated genes included nine known or putative protein kinases, eight type 2C protein phosphatases, and 35 transcription factors. 31 up-regulated and 35 down-regulated genes in esk1 mutants overlapped with that induced by cold acclimation. Some these genes were also regulated by abscisic acid treatment or by overexpressing of CBF/DREB transcription factors. Positional cloning of ESK1 gene uncovered a large family of plant-specific proteins whose function has not been previously characterized. The recessive nature of esk1 mutations and the wide-spectrum of genes altered in the mutants suggested the ESK1 protein may serve as a novel negative regulator of cold acclimation.