A role for diacylglycerol acyltransferase during leaf senescence
A role for diacylglycerol acyltransferase during leaf senescence
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DOI：
10.1104/pp.003087
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发表时间：
2002-08-01
期刊：
影响因子：
7.4
通讯作者：
Thompson, JE
中科院分区：
文献类型：
--
作者：
Kaup, MT;Froese, CD;Thompson, JE
来自拟南芥的莲座叶的脂质分析揭示了三酰甘油（TAG）的积累，随着叶片衰老的进行，与质体细胞的丰度和大小的增加相一致。拟南芥中TAG生物合成的末端步骤由二酰基甘油酰基转移酶1（DGAT 1; EC 2.3.1.20）催化。当从不同发育阶段的莲座叶分离的RNA的凝胶印迹用拟南芥表达的序列标签克隆E6132 T7（已被注释为DGAT 1）探测时，DGAT 1转录物水平的急剧增加在衰老叶中是明显的，与TAG的积累一致。DGAT 1转录本的增加与免疫学检测到的DGAT 1蛋白水平的提高在时间上相关。两条证据表明，衰老叶片的TAG是在叶绿体中合成的，并螯合从类囊体半乳糖脂的催化剂释放的脂肪酸。首先，从衰老叶中分离的TAG被证明富含十六碳三烯酸（16：3）和亚麻酸（18：3），这是通常存在于类囊体半乳糖脂中。第二，DGAT 1蛋白在衰老叶片中，被发现与叶绿体膜相关。这些发现共同表明，二酰基甘油酰基转移酶通过将从半乳糖脂脱酯化的脂肪酸螯合到TAG中而在衰老中起作用。这似乎是在叶片衰老过程中类囊体脂肪酸转化为韧皮部移动蔗糖的中间步骤。
Lipid analysis of rosette leaves from Arabidopsis has revealed an accumulation of triacylglycerol (TAG) with advancing leaf senescence coincident with an increase in the abundance and size of plastoglobuli. The terminal step in the biosynthesis of TAG in Arabidopsis is catalyzed by diacylglycerol acyltransferase 1 (DGAT1; EC 2.3.1.20). When gel blots of RNA isolated from rosette leaves at various stages of development were probed with the Arabidopsis expressed sequence tag clone, E6132T7, which has been annotated as DGAT1, a steep increase in DGAT1 transcript levels was evident in the senescing leaves coincident with the accumulation of TAG. The increase in DGAT1 transcript correlated temporally with enhanced levels of DGAT1 protein detected immunologically. Two lines of evidence indicated that the TAG of senescing leaves is synthesized in chloroplasts and sequesters fatty acids released from the catabolism of thylakoid galactolipids. First, TAG isolated from senescing leaves proved to be enriched in hexadecatrienoic acid (16:3) and linolenic acid (18:3), which are normally present in thylakoid galactolipids. Second, DGAT1 protein in senescing leaves, was found to be associated with chloroplast membranes. These findings collectively indicate that diacylglycerol acyltransferase plays a role in senescence by sequestering fatty acids de-esterified from galactolipids into TAG. This would appear to be an intermediate step in the conversion of thylakoid fatty acids to phloem-mobile sucrose during leaf senescence.