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The Scientific World Journal
Volume 2012, Article ID 565047, 9 pages
http://dx.doi.org/10.1100/2012/565047
Research Article

Distinct Mechanisms Regulating Gene Expression Coexist within the Fermentative Pathways in Chlamydomonas reinhardtii

1Department of Crop Plant Biology, University of Pisa, Via Mariscoglio 34, 56124 Pisa, Italy
2PlantLab, Institute of Life Sciences, Scuola Superiore Sant’Anna, Via Mariscoglio 34, 56124 Pisa, Italy
3Institute of Agricultural Biology and Biotechnology, National Research Council, Via Moruzzi 1, 56100 Pisa, Italy

Received 17 February 2012; Accepted 21 March 2012

Academic Editors: H. Acker and E. Tyystjarvi

Copyright © 2012 Larisa Angela Swirsky Whitney et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Under dark anoxia, the unicellular green algae Chlamydomonas reinhardtii may produce hydrogen by means of its hydrogenase enzymes, in particular HYD1, using reductants derived from the degradation of intercellular carbon stores. Other enzymes belonging to the fermentative pathways compete for the same reductants. A complete understanding of the mechanisms determining the activation of one pathway rather than another will help us engineer Chlamydomonas for fermentative metabolite production, including hydrogen. We examined the expression pattern of the fermentative genes PDC3, LDH1, ADH2, PFL1, and PFR1 in response to day-night cycles, continuous light, continuous darkness, and low or high oxygen availability, which are all conditions that vary on a regular basis in Chlamydomonas' natural environment. We found that all genes except PFL1 show daily fluctuations in expression, and that PFR1 differentiated itself from the others in that it is clearly responsive to low oxygen, where as PDC3, LDH1, and ADH2 are primarily under diurnal regulation. Our results provide evidence that there exist at least three different regulatory mechanisms within the fermentative pathways and suggest that the fermentative pathways are not redundant but rather that availability of a variety of pathways allows for a differential metabolic response to different environmental conditions.