THE EARLY GENETIC RESPONSE TO LIGHT IN THE GREEN UNICELLULAR ALGA CHLAMYDOMONAS-EUGAMETOS GROWN UNDER LIGHT DARK CYCLES INVOLVES GENES THAT REPRESENT DIRECT RESPONSES TO LIGHT AND PHOTOSYNTHESIS
THE EARLY GENETIC RESPONSE TO LIGHT IN THE GREEN UNICELLULAR ALGA CHLAMYDOMONAS-EUGAMETOS GROWN UNDER LIGHT DARK CYCLES INVOLVES GENES THAT REPRESENT DIRECT RESPONSES TO LIGHT AND PHOTOSYNTHESIS
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DOI：
10.1007/bf00040659
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发表时间：
1992-02-01
影响因子：
5.1
通讯作者：
GUERTIN, M
中科院分区：
文献类型：
--
作者：
GAGNE, G;GUERTIN, M
在绿色的单细胞衣原体真配子体中，细胞分裂很容易通过光/暗循环同步。在这些条件下，光启动子细胞的光合生长并开始GI期。受光照调控表达的基因可能是控制细胞增殖的重要机制。为了鉴定这些基因中的一些，用从用光刺激1小时或在同一时期保持在黑暗中（静止细胞）的细胞中提取的poly（A）+制备两个cDNA文库。为了将我们的分析限制在作为初级应答的一部分的那些基因，将细胞在放线菌酮存在下孵育。对每个文库中约40000个克隆进行差异筛选，发现44个克隆优先与来自光刺激细胞RNA的[P-32] cDNA探针杂交，15个克隆选择性地与来自静止细胞poly（A）+ RNA的[P-32] cDNA探针反应。这些克隆的交叉杂交鉴定了光诱导（LI）集合中的4个独立序列和未诱导（LR）文库中的2个独立序列。这些CDNAS中的四个对应于在光合作用激活时正或负调节的MRNAS。一个克隆代表在两个转换处短暂积累的mRNA。最后，LI 818 cDNA鉴定了一个新的叶绿素a/b结合（cab）基因家族，其mRNA积累受光和昼夜节律振荡器控制。内源性计时系统控制LI 818 mRNA的积累，使其先于光照开始数小时。另一方面，光影响LI 818 mRNA水平，独立于活跃的光合作用。
In the green unicellular alga Chlamydomonas eugametos, cellular division is readily synchronized by light/dark cycles. Under these conditions, light initiates photosynthetic growth in daughter cells and begins the GI phase. Genes whose expression is regulated upon illumination are likely to be important mechanisms controlling cell proliferation. To identify some of those genes, two CDNA libraries were prepared with poly(A)+ extracted from cells either stimulated with light for 1 h or held in darkness (quiescent cells) during the same period. To restrict our analysis to those genes that are part of the primary response, cells were incubated in presence of cycloheximide. Differential screening of approximately 40 000 clones in each library revealed 44 clones which hybridize preferentially with a [P-32] CDNA probe derived from RNA of light-stimulated cells and 15 clones which react selectively with a [P-32] CDNA probe synthesized from poly(A)+ RNA of quiescent cells. Cross-hybridization of these clones identified 4 independent sequences in the light-induced (LI) collection and 2 in the uninduced (LR) library. Four of these CDNAS correspond to MRNAS that are positively or negatively regulated upon activation of photosynthesis. One clone represents a MRNA that accumulates transitorily at both transitions. Finally, LI818 CDNA identifies a new chlorophyll a/b-binding (cab) gene family whose MRNA accumulation is controlled by light and a circadian oscillator. The endogenous timing system controls LI818 MRNA accumulation so that it precedes the onset of illumination by a few hours. On the other hand, light affects LI818 MRNA levels independently of active photosynthesis.