Mechanisms of signal transduction which controls carbon-dioxide fixation

Several chimeric constructs were generated by fusing series of 5'-upstream region of CAHl to the arylsulfatase reporter gene （ars）。Some Chlamydomonas cells transformed with the chimeric constructs expressed the reporter gene in res\to changes in the external CO D22-D2 concentration。5'上游区域被分成两个部分; a part function as a silencer in high-CO y D22 y D2 condition and the other part function as an enhancer in low-CO y D22 y D2 condition.Seven high-CO y D22 y D2-requiring mutants， which cannot grow as wild type Chamydomonas does in air level of CO y D22 y D2（0.04%）， were solated by gene tagging。It's indicated that these mutants carried lesions in genes related to the carbon concentrating Mechanism （CCM） or the signal transduction between sensing changes of environmental CO-D22-D2 concentration and induction of CCM-related genes。根据使用一个索引的PAC基因组学图书馆，两个突变体是互补的。突变C1是一个突变体，它是一个未累积的非有机碳（Ci）进入细胞，由一个含有20 kb基因组DNA的PAC克隆体补充。以下建议是，与运输相关的基因可能会在DNA片段中编码。另一个突变体C16，在低CO D22和D2中没有定义CCM相关基因的DNA片段，被转化为NIT 1固定位点的闪烁序列和转化者恢复了CCM相关基因的索引。克隆的DNA片段编码了一个基因，其中没有显示任何先前已知的基因的显著同源性。

Several chimeric constructs were generated by fusing series of 5'-upstream region of CAHl to the arylsulfatase reporter gene (ars) driven by βィイD22ィエD2-tublin minimal promoter. Some Chlamydomonas cells transformed with the chimeric constructs expressed the reporter gene in response to changes in the external COィイD22ィエD2 concentration. The 5'-upstream region is divided into two parts ; a part functions as a silencer in high-COィイD22ィエD2 condition and the other part functions as an enhancer in low-COィイD22ィエD2 condition.Seven high-COィイD22ィエD2-requiring mutants, which cannot grow as wild type Chlamydomonas does in air level of COィイD22ィエD2(0.04%), were isolated by gene tagging. It was indicated that these mutants carried lesions in genes related to the carbon concentrating mechanism (CCM) or the signal transduction pathway between sensing changes of environmental COィイD22ィエD2 concentration and induction of CCM-related genes. By using an indexed PAC genomic library, two mutants were complemented. The mutation of a mutant C1, which accumulate less inorganic carbon (Ci) into the cell, was complemented by a PAC clone containing 20-kb of genomic DNA. This suggests that Ci-transport related genes could be encoded within this DNA fragment. Another mutant C16, which does not induce CCM-related genes in low-COィイD22ィエD2, was transformed by a DNA fragment which correspond to the flanking sequences of the NIT1 insertional locus and the transformants recovered the induction of CCM-related genes. The cloned DNA fragment encoded a gene which does not show significant homology with any previously known genes.