Nitrogen starvation triggers signal transduction pathways that result in Chlamydomonas reinhardtii entering a cycle of sexual reproduction. A second signal cascade is triggered by blue light and results in the completion of gametogenesis. Two photoreceptors that respond to the blue region of the spectrum have been identified in C. reinhardtii and are encoded by the phototropin and cryptochrome genes Phot and CPH1, respectively. In April 21 early edition of the Proceedings of the National Academy of Sciences, Kaiyao Huang and Christoph F. Beck from the University of Freiburg, Germany, examined the role of phototropin in the control of the sexual life cycle of C. reinhardtii. They showed that diminished phototropin levels affect all three light-dependent stages of the sexual life cycle of this alga (PNAS, DOI:10.1073/pnas.0931459100, April 21, 2003).

Huang and Beck generated a Phot RNA interference (RNAi) knockdown mutant with transformants expressing only...

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