Identification of a Chlamydomonas reinhardtii gene (LTS3) important for the regulation of chlorophyll biosynthesis in the dark

Elena Chekunova1, Nataliya Savelieva1, and Bernhardt Grimm2

1) Department of Genetics, St.Petersburg State University, 7-9 Universitetskaya Nab. St. Petersburg, 199034, Russia 2) Institut fuer Biologie/Pflanzenphysiologie, Humboldt Universitaet, Philipstrasse 13, D-10115 Berlin, Germany

Unlike angiosperms, the green alga Chlamydomonas reinhardtii can synthesize chlorophyll in the dark. The genetic control of light-independent chlorophyll biosynthesis (CB) in Chlamydomonas has been investigated using two lts3-mutants (brc-1 and lts3) defective in the dark reaction of CB at a stage prior to protochlorophyllide to chlorophyllide conversion. The mutants in the heterotrophic conditions accumulate protoporphyrin IX (PP), MgPP, MgPPME and protochlorophyllide. After illumination they turn green. The mutant phenotype has been studied at the levels of pigment contents, activity of CB enzymes, and expression of the genes encoded of these enzymes. The nuclear LTS3 gene has been identified after positional cloning using a Chlamydomonas BAC library. It encodes a protein with a GATA1 domain. The mutant alleles carry alterations in the gene region coding for the GATA domain structure. We propose that the LTS3 encoded GATA-transcription factor activates the expression of certain genes encoding chlorophyll biosynthesis enzymes in the dark, e.g., the genes for Mg-chelatase and glutamate-1-semialdehyde aminotransferase. Supported by RFBR: 09-04-01646a.

e-mail address of presenting author: elena_chekunova@mail.ru