Characterization and genetic analysis of a low-temperature-sensitive mutant, sy-2, in Capsicum chinense
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A temperature-sensitive mutant of Capsicum chinense, sy-2, shows a normal developmental phenotype when grown above 24°C. However, when grown at 20°C, sy-2 exhibits developmental defects, such as chlorophyll deficiency and shrunken leaves. To understand the underlying mechanism of this temperature-dependent response, phenotypic characterization and genetic analysis were performed. The results revealed abnormal chloroplast structures and cell collapse in leaves of the sy-2 plants grown at 20°C. Moreover, an excessive accumulation of reactive oxygen species (ROS) resulting in cell death was detected in the chlorophyll-deficient sectors of the leaves. However, the expression profile of the ROS scavenging genes did not alter in sy-2 plants grown at 20°C. A further analysis of fatty acid content in the leaves showed the impaired pathway of linoleic acid (18:2) to linolenic acid (18:3). Additionally, the Cafad7 gene was downregulated in sy-2 plants. This change may lead to dramatic physiological disorder and alteration of leaf morphology in sy-2 plants by losing low-temperature tolerance. Genetic analysis of an F2 population from a cross between C. chinense ‘sy-2’ and wild-type C. chinense ‘No. 3341’ showed that the sy-2 phenotype is controlled by a single recessive gene. Molecular mapping revealed that the sy-2 gene is located at a genomic region of the pepper linkage group 1, corresponding to the 300 kb region of the Ch1_scaffold 00106 in tomato chromosome 1. Candidate genes in this region will reveal the identity of sy-2 and the underlying mechanism of the temperature-dependent plant response.
KeywordsLinolenic Acid Chloroplast Development Chloroplast Structure Photooxidative Damage COSII Marker
This work was carried out with the support of “the BioGreen21 program (Code20070301034022)”, RDA, and by Technology Development Program for Agriculture and Forestry, Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea.
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