Functional study of the molecular mechanism underlying transcription factor TDR4-regulated lycopene accumulation in tomato fruit
Date Issued
2012
Date
2012
Author(s)
Wu, Jin-Long
Abstract
It is well known that light treatment can induce the lycopene accumulation in tomato fruit, but which factors in light signaling and how these factors regulate this process are still unknown. In our previous studies, we compared the fruits of different tomato species that were treated with different light, and identified several gene candidates by suppression subtractive hybridization assay, which may be involved in the regulation of lycopene accumulation. Among them, one candidate is MADS-box transcription factor TDR4. We generated the reduction-of-function of TDR4 transgenic plants previously, and found that the expression levels of TDR4 were decreased, leading to a reduction of the levels of PSY, a key enzyme gene of the carotenoid biosynthesis. Besides, the fruit of the reduction-of-function of TDR4 transgenic plants contains a decreased level of the lycopene. So TDR4 may positively regulate the expression of PSY transcripts to modulate the lycopene accumulation. Thus, we are wondering whether TDR4 can directly regulate the expression of PSY, and whether TDR4 has other physiological functions. In this study, we used yeast one-hybrid, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays to prove that TDR4 can directly bind to the promoter and the intron region of PSY. Besides, we also found that TDR4 can bind to the promoters of some fruit ripening related genes such as CNR, ACS4, PG2a, PDS and TDR4 itself by ChIP assay. Furthermore, we generated the TDR4 promoter-driven gain-of-function of TDR4 transgenic plants. By analyzing the expression levels of TDR4 and TDR4-regulated genes in the fruits of wild type, gain-of-function and reduction-of-function of TDR4 transgenic lines, we found that TDR4 positively regulated the ripening-related and carotenoid biosynthetic genes. Moreover, the lycopene levels in the gain-of-function of TDR4 transgenic lines are higher than wild type, and the mature green fruit of the gain-of-function of TDR4 transgenic lines is more sensitive to blue light, resulting in more lycopene accumulation. Taken together, these data reveal that TDR4 is a key component in light-induced accumulation of lycopene, and may be also involved in fruit ripening.
Subjects
lycipene
tomato fruit
ethylene
Type
thesis
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