title: Induction of Maltose Release by Light in the Endosymbiont Chlorella variabilis of Paramecium bursaria.
abstract: The endosymbiotic green algae of Paramecium bursaria are known to release a photosynthate to the host cells. The endosymbiont Chlorella variabilis F36-ZK isolated in Japan releases maltose under acidic conditions, and such release requires both light and low pH. However, whether photosynthate release is due to light sensing by photoreceptors or is merely a consequence of active photosynthesis is unclear. Herein, we studied the effect of light on maltose release from C. variabilis F36-ZK; we measured maltose release using a combination of 1-phenyl-3-methyl-5-pyrazolone derivative and14C-tracer methods. Blue (450nm) or red (around 600nm) light was most effective to stimulate maltose release. This suggests that the photosynthetic pathway probably participates in maltose release, because the effective wavelength corresponds to the absorption spectrum of chlorophyll. Furthermore, maltose release was slightly affected by addition of a photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, but was abolished by another inhibitor of photosynthesis, 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone, suggesting that electron flow through photosystem I may be more involved in maltose release. Interestingly, starving F36-ZK cells cultured under prolonged dark conditions did not release maltose but retained their photosynthetic capacity. Our results thus show that maltose release is regulated by light and cellular conditions in endosymbiotic Chlorella.
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Aika
authors.initials: A
authors.lastname: Shibata
authors.affiliation: Department of Biotechnology, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Takahashi
authors.affiliation: Department of Biotechnology, College of Life Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kasahara
authors.affiliation: Department of Pharmacy, College of Pharmaceutical Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan. Electronic address: imamura@ph.ritsumei.ac.jp.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Imamura
mesh_terms: D002244:Carbon / Q000378:metabolism; D002708:Chlorella / Q000502:physiology* / Q000528:radiation effects; D007564:Japan; D008027:Light; D008320:Maltose / Q000378:metabolism*; D010247:Paramecium / Q000502:physiology*; D010788:Photosynthesis; D013559:Symbiosis
chemical_list: D008320:Maltose; D002244:Carbon
keywords: Carbon metabolism; Chlorella variabilis; endosymbiosis; maltose; maltose-release.