Gene Expression Phenotypes of Arabidopsis Associated with Sensitivity to Low Temperatures

Abstract

Chilling is a common abiotic stress that leads to economic losses in agriculture. By comparing the transcriptome of Arabidopsis under normal (22°C) and chilling (13°C) conditions, we have surveyed the molecular responses of a chilling-resistant plant to acclimate to a moderate reduction in temperature. The mRNA accumulation of approximately 20% of the approximately 8,000 genes analyzed was affected by chilling. In particular, a highly significant number of genes involved in protein biosynthesis displayed an increase in transcript abundance. We have analyzed the molecular phenotypes of 12 chilling-sensitive mutants exposed to 13°C before any visible phenotype could be detected. The number and pattern of expression of chilling-responsive genes in the mutants were consistent with their final degree of chilling injury. The mRNA accumulation profiles for the chilling-lethal mutants chs1, chs2, and chs3 were highly similar and included extensive chilling-induced and mutant-specific alterations in gene expression. The expression pattern of the mutants upon chilling suggests that the normal function of the mutated loci prevents a damaging widespread effect of chilling on transcriptional regulation. In addition, we have identified 634 chilling-responsive genes with aberrant expression in all of the chilling-lethal mutants. This reference gene list, including genes related to lipid metabolism, chloroplast function, carbohydrate metabolism and free radical detoxification, represents a potential source for genes with a critical role in plant acclimation to suboptimal temperatures. The comparison of transcriptome profiles after transfer of Arabidopsis plants from 22°C to 13°C versus transfer to 4°C suggests that quantitative and temporal differences exist between these molecular responses.