Light and Life; Light-Dependent DNA Processes in Marine Cyanobacteria
出版項
2020
說明
1 online resource (226 pages)
文字
text
無媒介
computer
成冊
online resource
附註
Source: Dissertations Abstracts International, Volume: 82-03, Section: B
Advisor: Bauer, Carl;Hangarter, Roger P
Thesis (Ph.D.)--Indiana University, 2020
Includes bibliographical references
Marine Synechococcus are a group of globally widespread and ecologically significant cyanobacteria that live in widely varying light conditions of oceanic waters. Cyanobacteria are photosynthetic organisms, and consequently their survival is restricted to the upper photic zone of the water column that is penetrated by light wavelengths to varying depths. Higher energy wavelengths penetrate the deepest with the exception of ultraviolet (UV) radiation that scatters through the water column not penetrating as deep as blue light. Lower energy red-shifted wavelengths are attenuated close to the surface. As is true of most cyanobacteria, marine Synechococcus have developed strategies to utilize the available light for efficient photosynthesis as well as for the repair of DNA damaged by UV radiation exposure.I have discovered that Synechococcus RS9916 (9916) can repair UV-induced DNA damage in a light-dependent manner, and that its genome encodes multiple distinct photolyase enzymes that can repair UV-induced DNA damage. Photolyases are enzymes that use the energy from blue light to repair the abnormal bonds formed between adjacent pyrimidine dimers. All currently analyzed marine Synechococcus strains and high-light Prochlorococcus ecotypes contain multiple photolyase genes, leading me to hypothesize this is a widely used DNA repair strategy for cyanobacteria living in UV-rich marine waters.RS9916 is also capable of undergoing chromatic acclimation, a process by which the light-harvesting photosynthetic antenna pigments can be changed to maximize the use of the wavelengths of light that are most abundant in the immediate environment. Chromatic acclimation offers cyanobacteria a survival advantage in fluctuating light environments as compared to similar organisms that cannot undergo chromatic acclimation. RS9916 Type IV chromatic acclimation is mediated by genes encoded within a small five kb genomic island. My research demonstrates that a short 165-bp gene on this genomic island, fciC, encodes a small protein that is essential for the transcriptional regulation of this process. I found that when blue light is more abundant than green light, FciA upregulates fciC, which then allows FciC to serially upregulate the transcription of two other genes encoded on the genomic island that are responsible for the changes to the chromophore composition of newly made phycobilisomes. We are now beginning to understand how Type IV Chromatic Acclimation is regulated in marine cyanobacteria
Electronic reproduction. Ann Arbor, Mich. : ProQuest, 2021
