Plastid lysophosphatidyl acyltransferase is essential for embryo development in arabidopsis
Plastid lysophosphatidyl acyltransferase is essential for embryo development in arabidopsis
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DOI：
10.1104/pp.103.035832
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发表时间：
2004-03-01
期刊：
影响因子：
7.4
通讯作者：
Huang, AHC
中科院分区：
文献类型：
--
作者：
Kim, HU;Huang, AHC
溶血磷脂酰酰基转移酶（LPAAT）是控制溶血磷脂酸在不同组织中代谢为不同磷脂酸的关键酶。对拟南芥基因组数据库的搜索揭示了五个可以编码LPAAT样蛋白的基因。我们确定了其中一个，LPAAT 1，是唯一的基因，编码质体LPAAT。LPAAT 1可以在功能上补充具有缺陷LPAAT的细菌突变体。用LPAAT 1转化的细菌产生的LPAAT在18：1-溶血磷脂酸存在下对16：0-辅酶A的体外酶活性远高于对18：1-辅酶A的体外酶活性。LPAAT 1基因在不同器官中均有表达，在绿色叶中表达量最高。鉴定了具有插入到LPAAT 1中的T-DNA的突变体。杂合突变体没有明显的表型，其叶酰基组成与野生型相似。一个杂合突变体的自交产生正常大小的种子和孟德尔比率为3：1的皱缩种子，并且皱缩种子不能发芽。萎缩的种子显然是T-DNA插入的LPAAT 1的纯合，并且其中的胚胎发育在心型鱼雷阶段被阻止。这种胚胎致死性可以通过用35 S：LPAAT 1构建体转化杂合突变体来挽救。目前发现的胚胎死亡的纯合敲除突变体的质体LPAAT与早期发现的正常表型的纯合突变体缺乏的质体甘油-3-磷酸酰基转移酶;这两种突变阻止质体磷脂酸的合成。两个突变体的对比表型之间的差异的原因进行了讨论。
Lysophosphatidyl acyltransferase (LPAAT) is a pivotal enzyme controlling the metabolic flow of lysophosphatidic acid into different phosphatidic acids in diverse tissues. A search of the Arabidopsis genome database revealed five genes that could encode LPAAT-like proteins. We identified one of them, LPAAT1, to be the lone gene that encodes the plastid LPAAT. LPAAT1 could functionally complement a bacterial mutant that has defective LPAAT. Bacteria transformed with LPAAT1 produced LPAAT that had in vitro enzyme activity much higher on 16:0-coenzyme A than on 18:1-coenzyme A in the presence of 18:1-lysophosphatidic acid. LPAAT1 transcript was present in diverse organs, with the highest level in green leaves. A mutant having a T-DNA inserted into LPAAT1 was identified. The heterozygous mutant has no overt phenotype, and its leaf acyl composition is similar to that of the wild type. Selfing of a heterozygous mutant produced normal-sized and shrunken seeds in the Mendelian ratio of 3:1, and the shrunken seeds could not germinate. The shrunken seeds apparently were homozygous of the T-DNA-inserted LPAAT1, and development of the embryo within them was arrested at the heart-torpedo stage. This embryo lethality could be rescued by transformation of the heterozygous mutant with a 35S:LPAAT1 construct. The current findings of embryo death in the homozygous knockout mutant of the plastid LPAAT contrasts with earlier findings of a normal phenotype in the homozygous mutant deficient of the plastid glycerol-3-phosphate acyltransferase; both mutations block the synthesis of plastid phosphatidic acid. Reasons for the discrepancy between the contrasting phenotypes of the two mutants are discussed.