A temperature-sensitive mechanism that regulates post-translational stability of a plastidial ω-3 fatty acid desaturase (FAD8) in Arabidopsis leaf tissues
A temperature-sensitive mechanism that regulates post-translational stability of a plastidial ω-3 fatty acid desaturase (FAD8) in Arabidopsis leaf tissues
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DOI：
10.1074/jbc.m407226200
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发表时间：
2005-02-04
影响因子：
4.8
通讯作者：
Iba, K
中科院分区：
文献类型：
--
作者：
Matsuda, O;Sakamoto, H;Iba, K
三烯脂肪酸（TAs）是植物膜脂的主要成分。在拟南芥中，ω - 3脂肪酸去饱和酶的两种质体同工酶FAD7和FAD8是叶片组织中三烯脂肪酸产生的主要贡献者。尽管这两种同工酶在结构上高度相关，但它们的活性对温度的响应受到不同的调节。由于FAD8活性对温度敏感，升高的温度会导致叶片三烯脂肪酸水平下降。一系列FAD7 - FAD8嵌合基因（每个都编码一种有功能的质体ω - 3去饱和酶）被引入拟南芥fad7 fad8双突变体中。对带有或不带有c - Myc表位标签的构建体进行了测试。通过Northern和Western分析以及检测脂肪酸组成来测定每个嵌合基因对温度的响应功能。所有携带含有FAD8衍生的C末端编码区（44个氨基酸）的嵌合基因的转化体在暴露于高温时都显示出三烯脂肪酸水平显著下降，这与用FAD8天然形式互补的转基因株系情况相似。三烯脂肪酸水平的降低伴随着ω - 3去饱和酶蛋白量的减少，但不一定伴随着其转录水平的降低。在抑制蛋白质合成后对c - Myc标记产物的降解分析表明，FAD8衍生的C末端区域以一种自动调节的方式在高温下使蛋白质不稳定。这表明FADS翻译后稳定性的调节为响应温度改变其活性提供了一种重要的调节机制，介导了在升高温度下三烯脂肪酸水平的降低。
Trienoic fatty acids (TAs) are the major constituents in plant membrane lipids. In Arabidopsis, two plastidial isozymes of omega-3 fatty acid desaturase, FAD7 and FAD8, are the major contributors for TA production in leaf tissues. Despite a high degree of structural relatedness, activities of these two isozymes are regulated differentially in response to temperature. Elevated temperatures lead to decreases in leaf TA level due to temperature sensitivity of FAD8 activity. A series of FAD7-FAD8 chimeric genes, each encoding a functional plastidial w-3 desaturase, were introduced into the Arabidopsis fad7fad8 double mutant. Constructs with or without a c-Myc epitope tag were tested. Functionality of each chimeric gene in response to temperature was assayed by Northern and Western analyses and by examining the fatty acid composition. All transformants harboring a chimeric gene containing the FAD8-derived C-terminal coding region (44 amino acids) showed a marked decrease in TA level when exposed to high temperature, similarly as transgenic lines complemented with the native form of FAD8. The reduction of TA level was accompanied by a decrease in the amount of omega-3 desaturase protein but not necessarily by a decrease in its transcript level. Analysis of the decay of c-Myc-tagged products after inhibiting protein synthesis revealed that the FAD8-derived C-terminal region acts in an autoregulatory fashion to destabilize the protein at high temperature. This suggests that the regulation of post-translational stability of FADS provides an important regulatory mechanism for modifying its activity in response to temperature, mediating a decrease in TA level at elevated temperatures.