Understanding chilling tolerance traits using arabidopsis chilling-sensitive mutants

Abstract

Many plants of tropical and subtropical origin are severely damaged when exposed to chilling temperatures between 2 and 15°C. In contrast, the cruciferous plant Arabidopsis thaliana is chilling tolerant and, therefore provides an alternative model plant system for the identification of chilling tolerance traits. In this chapter, we describe physiological, biochemical, and molecular responses of Arabidopsis class 1 chilling-sensitive (chs) mutants to low temperatures. These mutants, including chs1, chs2 and chs3, are extremely chilling-sensitive and wilt and turn yellow in just a few days after transfer to low temperatures of 4–13°C. Overall, following exposure to chilling, class 1 chs mutants suffer from: (1) loss of chlorophyll and decrease in photosynthetic efficacy resulting in lack of starch accumulation, (2) damage to cellular membranes resulting in increased electrolyte leakage, and (3) accumulation of the reactive oxygen species (ROS) hydrogen peroxide (H2O2). At the molecular level, transcriptome analysis studies following exposure to 10°C for 48 h using the Affymetrix ATH1 genome array reveal remarkable changes in expression patterns of between 1,500 and 3,000 genes, which are significantly differentially expressed (p≤ 0.05 and up or down-regulated by a factor of at least 4) in chs1, chs2, and chs3 mutants compared to wild-type (WT) plants. The main functional categories of up-regulated genes by chilling include “stress,” “protein,” and “signaling,” whereas the main categories down-regulated by chilling were “photosynthesis,” “tetrapyrrole synthesis,” “carbohydrate metabolism,” “cell wall,” and “lipid metabolism”. Overall, these and other studies using Arabidopsis chilling-sensitive mutants allow the recognition of major genetic traits crucial for plant survival under chilling conditions.