Transcriptional regulatory network of genes for carbon concentrating mechanisms

莱茵衣藻通过可能的信号转导途径诱导一组碳浓缩机制(CCM)基因，从而适应低CO_2供应、强光等环境胁迫。几个CCM相关基因的表达是由低CO_2诱导的，其中Cahl编码周质碳酸失碳酶(CA)，MCA编码线粒体CA，Ccpl编码叶绿体被膜蛋白LIP-36。这种对CO_2限制条件的适应表明存在细胞感知CO_2缺乏的感觉机制和信号转化为特定基因调控的途径。我们已经克隆了一个核调控基因CCML，它补充了多效性高CO_2要求突变的C16(Fukuzawa等人)的突变。2001)。CCML在高CO_2和低CO_2条件下均呈结构性表达。CCM1锌指基序中的His-54对其调节功能是必不可少的。为了分离受CCM1控制的靶基因，我们开发了包含10,368个EST的cDNA大阵列(Fukuzawa等人)。从高CO_2或低CO_2培养的WT细胞和低CO_2驯化的C16细胞中提取的RNA样品，用β&lt；33&gt；P-dCTP标记，并与DNA阵列膜杂交。在C16突变体中未诱导出59个低CO_2诱导的EST克隆，表明这些克隆受CCM11的调控。EST克隆的时间相关表达模式使我们能够检测到包含光呼吸或离子转运蛋白的低CO_2诱导(LCI)基因。还将讨论CO_2限制胁迫与光呼吸或强光胁迫的关系，以及通过对调控突变体的阵列分析得出的CO_2信号转导途径。

Chlamydomonas reinhardtii can acclimate to environmental stresses such as low CO_2-supply, high-light by inducing a set of genes for a carbon-concentrating mechanism (CCM) through putative signal transduction pathways. Expression of several CCM-related genes, Cahl coding for a periplasmic carbonic anhydrase (CA), Mca for a mitochondrial CA and Ccpl for a chloroplast envelope protein LIP-36, is induced by lowering CO_2. This acclimation to CO_2-limiting conditions suggests the existence of sensory mechanisms by which cells perceive the shortage of CO_2 and pathways by which the signal is transduced into the specific gene regulation. We have cloned a nuclear regulatory gene, Ccml, which complements the mutation in the pleiotropic high-CO_2 requiring mutant C16 (Fukuzawa et.al. 2001). Ccml is constitutively expressed both in high- and low-CO_2 conditions. His-54 in the zinc-finger motif of CCM1 is essential to its regulatory function. To isolate target genes, which are controlled by CCM1, we have developed cDNA macroarray containing 10,368 EST (Fukuzawa et al.). RNA samples from WT cells cultured in high-CO_2 or low-CO_2 and also from the low-CO_2-acclimated C16 were labeled with ^<33>P-dCTP and hybridized with cDNA array membranes. Fifty-nine low-CO_2 inducible EST clones were not induced in the C16 mutant, suggesting that these are regulated by CCM1l. Time-dependent expression patterns of EST clones enabled us to detect low-CO_2 inducible (Lci) genes containing those for photorespiration or ion-transporters. Relationship between CO_2-limiting stress and photorespiration or high-light stress will be discussed as well as CO_2-signal transduction pathways deduced from array analyses of regulatory mutants.