Mechanisms of signal transduction which controls carbon-dioxide fixation

Several chimeric constructs were generated by fusing series of 5'-upstream region of CAHl to thearylsulfatase reporter gene （ars）驱动程序由β D22 -tublin minimal promoter. Some Chlamydomonascells transformed with the chimeric constructs expressed the reporter gene in response to change inthe external CO - D22 - D2 concentration. the 5'-upstream region is divided into two parts；a part functions as a silencer in high-CO - 22 - D2 condition and the other part functions as anenhancer in low-CO - D22 - D2 condition.Seven high-CO - D22 -requiring mutants，which cannot grow as wild type Chlamydomonas does in air level of CO - D22 - D2(0.04%)，isolated by gene tagging. It was indicated that these mutants carried lesions in genes relatedto the carbon concentrating mechanism (CCM) or the signal transduction pathway between sensingchanges of environmental CO D22 - D2 concentration and induction of CCM-related genes. By using an独立PAC genomic library， two mutants were complemented. The mutation of a mutant C1，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相关的基因可以encoded within this DNA fragment. Another mutant C16，which does not induce CCM-related genes in low-CO - D22 - D2was transformed by a DNA fragment which correspond to the flanking sequences of the NIT1 insertionallocus and the transformants recovered the induction of CCM-related genes. the cloned DNA fragmentencoded a gene which does not show significant homology with any previously known genes。

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.