Three Acyltransferases and Nitrogen-responsive Regulator Are Implicated in Nitrogen Starvation-induced Triacylglycerol Accumulation in Chlamydomonas
Three Acyltransferases and Nitrogen-responsive Regulator Are Implicated in Nitrogen Starvation-induced Triacylglycerol Accumulation in Chlamydomonas
复制标题
DOI：
10.1074/jbc.m111.334052
复制
发表时间：
2012-05-04
影响因子：
4.8
通讯作者：
Merchant, Sabeeha S.
中科院分区：
文献类型：
--
作者：
Boyle, Nanette R.;Page, Mark Dudley;Merchant, Sabeeha S.
藻类最近作为生物柴油的潜在来源而受到关注;然而，关于导致三酰基甘油产生的生物触发因素仍有很多未知之处。我们使用RNA-Seq作为发现衣原体中负责三酰甘油（TAG）产生的基因和激活该途径的调控成分的工具。三个基因编码酰基转移酶，DGAT 1，DGTT 1和PDAT 1，诱导氮饥饿和可能有一个TAG积累的基础上，他们的表达模式的作用。DGAT 1和DGTT 1在其他TAG积累条件下（缺硫、缺磷、缺锌和缺铁）也显示mRNA丰度增加。插入突变体pdat 1 -1和pdat 1 -2积累的TAG比亲本菌株CC-4425少25%，这证明了衣原体转酰化途径的相关性。DGTT 1和PDAT 1的生化功能通过在缺乏所有酰基转移酶活性的酵母菌株中拯救油酸敏感性和恢复TAG积累来验证。时程分析表明，SQUAMOSA启动子结合蛋白结构域转录因子，其mRNA的增加先于脂质生物合成基因如DGAT 1，是氮缺乏反应的候选调节因子。一个插入突变体，nrr 1 -1，积累只有50%的TAG与亲本菌株相比，在氮饥饿条件下，不受其他营养胁迫，这表明该调节器的特异性氮剥夺条件。
Algae have recently gained attention as a potential source for biodiesel; however, much is still unknown about the biological triggers that cause the production of triacylglycerols. We used RNA-Seq as a tool for discovering genes responsible for triacylglycerol (TAG) production in Chlamydomonas and for the regulatory components that activate the pathway. Three genes encoding acyltransferases, DGAT1, DGTT1, and PDAT1, are induced by nitrogen starvation and are likely to have a role in TAG accumulation based on their patterns of expression. DGAT1 and DGTT1 also show increased mRNA abundance in other TAG-accumulating conditions (minus sulfur, minus phosphorus, minus zinc, and minus iron). Insertional mutants, pdat1-1 and pdat1-2, accumulate 25% less TAG compared with the parent strain, CC-4425, which demonstrates the relevance of the trans-acylation pathway in Chlamydomonas. The biochemical functions of DGTT1 and PDAT1 were validated by rescue of oleic acid sensitivity and restoration of TAG accumulation in a yeast strain lacking all acyltransferase activity. Time course analyses suggest than a SQUAMOSA promoter-binding protein domain transcription factor, whose mRNA increases precede that of lipid biosynthesis genes like DGAT1, is a candidate regulator of the nitrogen deficiency responses. An insertional mutant, nrr1-1, accumulates only 50% of the TAG compared with the parental strain in nitrogen-starvation conditions and is unaffected by other nutrient stresses, suggesting the specificity of this regulator for nitrogen-deprivation conditions.