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The presence of the chlorophyll cycle in chlorophyll b-containing cyanobacteria implicated by the in vitro activity assay
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| Title: | The presence of the chlorophyll cycle in chlorophyll b-containing cyanobacteria implicated by the in vitro activity assay |
| Other Titles: | In vitroにおける活性測定によって示された、クロロフィルbを合成するシアノバクテリアにおけるクロロフィルサイクルの存在 |
| Authors: | HYUNSEOK, LIM Browse this author |
| Keywords: | Chlorophyll cycle | | 7-hydroxymethyl chlorophyll a reductase (HCAR) | | Chlorophyll b reductase (CBR) | | Prochlorothrix hollandica | | Acaryochloris RCC1774 |
| Issue Date: | 25-Mar-2020 |
| Publisher: | Hokkaido University |
| Abstract: | In plants, chlorophyll a and b are interconvertible by the action of three enzymes – chlorophyllide a oxygenase, chlorophyll b reductase (CBR), and 7-hydroxymethyl chlorophyll a reductase (HCAR). These reactions are collectively referred to as the chlorophyll cycle. In plants, this cyclic pathway ubiquitously exists and plays essential roles in acclimation to different light conditions at various developmental stages. In contrast, only a limited number of cyanobacteria species produce chlorophyll b, and these include Prochlorococcus, Prochloron, Prochlorothrix, and Acaryochloris. In this study, we investigated a possible existence of the chlorophyll cycle in chlorophyll-b synthesizing cyanobacteria. First, we selected CBR and HCAR homologues from Prochlorothrix hollandica and Acaryochloris RCC1774 genomes and tested whether their gene products show CBR or HCAR activity in vitro by overexpressing them in Escherichia coli. All of these proteins show CBR and HCAR activity in vitro, respectively, indicating that both cyanobacteria possess the chlorophyll cycle. It is also found that CBR and HCAR homologues exist only in the chlorophyll b-containing cyanobacteria that habitat shallow seas or fresh water, where light conditions change dynamically, while they are not found in Prochlorococcus species that usually habitat environments with fixed lighting. Thus, it is hypothesized the chlorophyll cycle also contributes to light acclimation in cyanobacteria. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第13949号 |
| Degree Level: | 博士 |
| Degree Discipline: | 生命科学 |
| Examination Committee Members: | (主査) 准教授 田中 亮一, 教授 内藤 哲, 教授 加藤 敦之 |
| Degree Affiliation: | 生命科学院（生命科学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/80054 |
| Appears in Collections: | 課程博士 (Doctorate by way of Advanced Course) > 生命科学院(Graduate School of Life Science)
学位論文 (Theses) > 博士 （生命科学）
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