Abstract: 【Objective】Cold stress is one of the factors influencing the quality and quantity of crops while the epicuticular wax is believed to be the first protective barrier of the plant to external stresses. In the current study, the effects of cold stress on epicuticular wax morphology and constituents and expression of wax related genes in Arabidopsis stems were examined, aiming to understand the interactive mechanism between plant epicuticular wax and cold stress, and to provide suggestions on researches related to crop resistance to abiotic stresses. 【Method】The materials used in current experiment included wild type Arabidopsis (WT) and wax mutants (cer1, cer3, cer4, cer6, cer10, cer20 and kcs1). The seedlings were grown for 5-6 weeks after germination, and then were placed in a temperature controlled cabinet at 4℃ for ten days and eighteen days, seperately. Scanning electron microscope technology was used to investigate the changes of crystal structure. Gas chromatography and mass spectrometry technology were used to measure the contents of total wax and wax constituents. Real-time Q-PCR was used to analyze the transcripts of wax related genes.【Result】Under cold stress, the density, shape and size of wax crystalloids on stem of mutants and WT changed. Wax crystal structures on WT fused to big horizontal plates, greatly covering the surface of stems, which might help protect plant from cold hardness and decrease water loss. The pine-needle crystals on cer1 reduced significantly and some small dendrites appeared. The rod crystals on cer3 and cer10 reduced significantly while the crystals on cer6 and cer20 increased. The vertical rods on kcs1 surface reduced while the horizontal rods appeared with the fusion of crystals. The cold stress had no effect on the crystal morphology on cer4. The GC-MS analysis showed that the contents of wax constituents and total wax also changed under cold stress. The contents of aldehydes and ketones in Arabidopsis wild type reduced significantly while the content of primary alcohols increased. For the mutants, the contents of acids, aldehydes and ketones increased or changed insignificantly while the contents of primary alcohols reduced or changed insignificantly. For cer3 and cer10 with severe cold harm symptoms, the contents of primary alcohols decreased significantly. The contents of wax accumulated significantly under cold stress except cer3 and cer10, mainly attributing to significant increase in alkanes and secondary alcohols. The content of total wax in cer3 changed insignificantly while that in cer10 reduced. For A. thaliana wild type, the expression of CER1 was induced strongly by the cold stress, suggesting that plant can up-regulate the expression of CER1 to promote the alkane synthesis under cold stress. The up-regulated expression of CER4 promoted the synthesis of primary alcohol. The down-regulated expression of KCS1, CER3 and WIN1 under cold stress indicated that the increase of total wax was due to the promotion of the alkane-synthesizing branch. 【Conclusion】 The crystal structure and constituents of epicuticular wax can be altered by cold stress, and the increase of alkanes and secondary alcohols in epiculticular wax might be the main response way to cold stress. The increase of alkanes contributes to the increase of total wax and cer1 might be the main response wax-related gene to cold stress for A. thaliana.

Key words: Arabidopsis thaliana , cold stress , epicuticular wax , gene , wax mutants