Identification of blue light-induced genes involved in the lycopene accumulation of Lycopersicon esculentum fruit
Date Issued
2006
Date
2006
Author(s)
Lee, Te-Cheng
DOI
zh-TW
Abstract
Carotenoids are rich in ripening tomato fruit and made up of lycopenes (~90%), β-carotenes (~5-10%) and luteins (~1-5%), providing nutritional benefits as precursors to essential vitamins and as antioxidants. Although genes involved in carotenoid biosynthesis have been extensively studied, regulatory mechanisms responsible for the process remain largely unknown. Lycopenes are not accumulated under high temperature. Whether lycopene accumulations are different between heat-tolerant and nonheat-tolerant tomatoes remain to be elucidated. Thus, the thesis is intented to understand the differences in lycopene accumulations between heat-tolerant tomato and nonheat-tolerant tomato under various light treatments and also to identify light-regulated factors involved in the control of lycopene levels of tomato fruit.
Tomato fruits of different cultivars (CL5915, CL5675, L18 and CHT1200) at mature green stage were treated with different light sources and found that blue light, in addition to red light, can increase lycopene levels, especially in heat-tolerant tomato lines (CL5915、L18). So we chose the super heat tolerant CL5915 line for further studies. Use blue light treated tomato fruit cDNA as tester, dark treated tomato fruit cDNA as driver to perform suppression subtractive hybridization (SSH). Sixteen genes were shown to have differential expression patterns between dark and blue light treated tomato fruits. Four of these 16 genes were expressed in higher levels under blue light and other 12 genes were expressed more in the dark than in the blue light. We chose 4 candidate genes for further functional studies based on literature search : (1) Lycopersicon esculentum vacuolar proton ATPase proteolipid subunit (LeV-ATPase), (2) Lycopersicon esculentum TDR4 transcription factor (LeTDR4), (3) Lycopersicon esculentum phytoene synthase (LePSY), (4) Lycopersicon esculentum S-adenosyl-l-homocysteine hydrolase (LeSAHH). Tissue specific expression studies indicated that all of them were expressed at the red ripe stage of tomato fruit. Besides, the expression of LeTDR4, LePSY and LeSAHH can be induced by light and the expression levels of LeTDR4 and LePSY are positively correlated with lycopene accumulations. Further, using virus-induced gene silencing (VIGS) to knock down the expression of LeTDR4, LePSY and LeSAHH genes in tomato fruits indeed reduced lycopene levels. Taken together, LeTDR4, LePSY and LeSAHH genes isolated by SSH are involved in the regulation of lycopene levels of tomato fruit.
Subjects
番茄
茄紅素
藍光
tomato
lycopene
blue light
VIGS
suppression subtractive hybridization
Type
other
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