Mammalian anti-apoptotic gene Bcl-xL promotes tolerance of photooxidative stress in the green alga Chlamydomonas reinhardtii
Julian N. Rosenberg1, Wipawee Dejtisakdi2, Stephen M. Miller2, Michael J. Betenbaugh1, and George A. Oyler3,4
1) Deptartment of Chemical & Biomolecular Engineering, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218
2) Department of Biological Sciences, University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
3) Advanced Technology Laboratory, Johns Hopkins University, 800 Wyman Park Dr, Baltimore, MD 21218
4) Department of Biochemistry, University of Nebraska-Lincoln, 1901 Vine Street, Lincoln, NE 68588
Whether in the context of a multicellular organism or a microbial population, programmed cell death (PCD) is characterized by the organized self-destruction of individual cells that may pose a threat to the integrity of the group. This altruistic behavior, more specifically defined as apoptosis, is triggered by a number of environmental stresses, including photooxidative cellular damage. B-cell lymphoma-extra large (Bcl-xL) protein is a strong mammalian cell death inhibitor that intervenes in the signal transduction pathway of apoptosis; yet, PCD is a well-conserved evolutionary trait in both animals and plants alike. For biotechnological purposes, the exploitation of microalgae for recombinant protein and biofuel production could benefit from improved cell viability during periods of high irradiance. In an attempt to overcome this obstacle to productivity, C. reinhardtii was genetically transformed with a codon-optimized fusion of Venus and Bcl-xL. Venus is an improved variant of yellow fluorescent protein; positive transformants were verified by genomic PCR. Nuclear expression of Bcl-xL, driven by the C. reinhardtii hsp70/rbcS2 tandem promoter and confirmed with RT-PCR, was shown to enhance the ability of C. reinhardtii to survive conditions of stress induced by reactive oxygen species generated with the photosensitizing dye Rose Bengal.
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