| Abstrakt: |
Etiolated leaves of 28°C-dark-grown mung bean (Vigna radiataL. cv. 2937) seedlings fail to turn green after being shifted to a light and cold environment. At the visible phenotypic level, incapability of leaf greening is the only failure event for the de-etiolation of mung bean seedlings at low temperature. Ultrastructural studies revealed that chloroplast development was completely suppressed by chilling treatment. A cDNA library originating from 28°C-light-grown seedling leaves was constructed for screeningcold-suppressed (cos) genes. Thirteen full-length cDNA clones were obtained, with 12 clones encoding chloroplast proteins, which, according to their known physiological functions, were important for chloroplast development and photosynthesis. AnothercoscDNA encodes CYP90A2, which is a cytochrome P450 protein involved in the biosynthesis of brassinosteroid hormones. Allcosgenes are light-regulated at normal temperature. The influence of chilling stress oncosexpression was examined in 10°C-light- and 10°C-dark-grown etiolated seedlings, and in 10°C-light-grown green plants. The data show thatcosexpression in these three treatments is severely suppressed. This suppression is controlled at the transcriptional level, as demonstrated by nuclear runoff experiments, and is reversible becausecosmRNAs accumulate again after the cold-treated plants have been transferred to 28°C. [ABSTRACT FROM AUTHOR] |
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