Regulation of tomato fruit polygalacturonase mRNA accumulation by ethylene: A re-examination
Regulation of tomato fruit polygalacturonase mRNA accumulation by ethylene: A re-examination
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DOI：
10.1104/pp.116.3.1145
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发表时间：
1998-03-01
期刊：
影响因子：
7.4
通讯作者：
Bennett, AB
中科院分区：
文献类型：
--
作者：
Sitrit, Y;Bennett, AB
多聚半乳糖醛酸酶（PG）是果实成熟过程中负责果胶分解的主要酶。尽管对果实中PC基因表达的调控因素进行了广泛的研究，但关于乙烯在介导其表达中的作用存在相互矛盾的证据。利用转基因番茄（Lycopersicon esculentum）果实，通过表达1-aminocyclopropane-1 -carboxylic acid（ACC）合成酶反义基因抑制内源乙烯的产生，重新研究了果实成熟过程中乙烯对PC mRNA、酶活性和蛋白质积累的调控作用。用低至0.1 - 1 μ L/L的乙烯处理转基因反义ACC合酶成熟绿色果实24 h，诱导PC mRNA积累，并且这种积累在乙烯浓度高达100 μ L/L时更高。无论是PC酶的活性，也不PC蛋白积累在这24小时内的乙烯处理，表明翻译滞后至少24小时后PC mRNA的积累，即使在高乙烯浓度。当在10 μ L/L的浓度下检测时，PC mRNA在乙烯处理的6小时内积累，表明PC基因对乙烯反应迅速。处理转基因番茄果实与低水平的乙烯（0.1 μ L/L）长达6天诱导水平的PC mRNA，酶活性，和蛋白质6天后，这是在成熟的野生型水果中观察到的水平相媲美。一个类似的水平的内部乙烯（0.15 μ L/L），在转基因反义ACC合酶果实收获后保持28天。在这些果实中检测PC mRNA、酶活性和蛋白质。总的来说，这些结果表明，PC mRNA的积累是乙烯调节，乙烯所需的低阈值水平，以促进PC mRNA的积累可能会超过，即使在转基因反义ACC合酶番茄果实。
Polygalacturonase (PG) is the major enzyme responsible for pectin disassembly in ripening fruit. Despite extensive research on the factors regulating PC gene expression in fruit, there is conflicting evidence regarding the role of ethylene in mediating its expression. Transgenic tomato (Lycopersicon esculentum) fruits in which endogenous ethylene production was suppressed by the expression of an antisense 1-aminocyclopropane-1 -carboxylic acid (ACC) synthase gene were used to re-examine the role of ethylene in regulating the accumulation of PC mRNA, enzyme activity, and protein during fruit ripening. Treatment of transgenic antisense ACC synthase mature green fruit with ethylene at concentrations as low as 0.1 to 1 mu L/L for 24 h induced PC mRNA accumulation, and this accumulation was higher at concentrations of ethylene up to 100 mu L/L. Neither PC enzyme activity nor PC protein accumulated during this 24-h period of ethylene treatment, indicating that translation lags at least 24 h behind the accumulation of PC mRNA, even at high ethylene concentrations. When examined at concentrations of 10 mu L/L, PC mRNA accumulated within 6 h of ethylene treatment, indicating that the PC gene responds rapidly to ethylene. Treatment of transgenic tomato fruit with a low lever of ethylene (0.1 mu L/L) for up to 6 d induced levels of PC mRNA, enzyme activity, and protein after 6 d, which were comparable to levels observed in ripening wild-type fruit. A similar level of internal ethylene (0.15 mu L/L) was measured in transgenic antisense ACC synthase fruit that were held for 28 d after harvest. In these fruit PC mRNA, enzyme activity, and protein were detected. Collectively, these results suggest that PC; mRNA accumulation is ethylene regulated, and that the low threshold levels of ethylene required to promote PC mRNA accumulation may be exceeded, even in transgenic antisense ACC synthase tomato fruit.