In order to maximize growth and development, photosynthetic organisms sense and respond to changes in their photoenvironment. Many cyanobacteria possess the ability to alter the protein composition of their light-harvesting complexes in response to changes in the prevalent colors of light in their environment. This process is termed complementary chromatic adaptation (CCA) and, in Fremyella diplosiphon, is most responsive to red and green illumination. CCA is controlled by a photosensory biliprotein, RcaE (regulator of chromatic adaptation). To increase knowledge about the molecular basis of CCA, the goals of this project are: (1) to investigate the biosynthesis of RcaE; (2) to elucidate the molecular mechanism by which RcaE perceives red and green light; and (3) to characterize the downstream effectors to which RcaE transmits the perceived light signal. Molecular genetic and biochemical approaches will be employed to accomplish these goals. As RcaE is one of only a few members of the prokaryotic class of phytochrome-related proteins closely linked to a discrete physiological phenomenon, elucidation of the RcaE regulatory gene network that controls growth and development in response to light is expected to provide insight into the mechanisms of operation of biliprotein-regulated photomorphogenesis in photosynthetic systems.
Broader Impacts: In addition to the training of graduate students and postdoctoral scholars, broader impacts of the research will include an influence on undergraduate science majors and students from underrepresented groups, including women and participants in the Charles Drew Science Enrichment Program at Michigan State University. A training component of the research will be designed, in part, to develop the ability of these students to think analytically and critically. This career development plan also includes the utilization of instructional methods that enhance students' critical thinking skills, scientific literacy, and technical proficiency. The educational focus incorporates the use and evaluation of active learning pedagogies in an undergraduate biochemistry survey course.
Intellectual Merit: In order to maximize growth and development, photosynthetic organisms sense and respond to changes in their external environment. Sensing the environmental changes that occur is vitally important as these organisms mostly have limited abilities to move. Thus, they must sense and respond to external changes to maximize their abilities to utilize light for energy production during the process of photosynthesis, while simultaneously minimizing the potential damaging impacts of excess light or ultraviolet light exposure. Such decisions require that these organisms balance their energy supply to attribute energy to perceiving the wavelengths, brightness, direction and duration of light with the demands for energy for initiating genetic and physiological changes to respond to the light available and other required metabolic activities. Many cyanobacteria possess the ability to alter the protein composition of their light-harvesting complexes in response to changes in the prevalent colors of light in their environment. This process is termed complementary chromatic adaptation (CCA) and, in the organism Fremyella diplosiphon which was the focus on our studies, is most responsive to red and green illumination. CCA is controlled by a light-responsive protein, RcaE (regulator of chromatic adaptation), which is activated or turned "on" in response to light exposure. To increase knowledge about the molecular basis of CCA, the goals of this project were to investigate (1) when and how RcaE is synthesized in the cell, (2) to understand the biochemical means by which the protein perceives red and green light and (3) to investigate how the activated protein transfers the light status signal to other cellular components to impact the pigmentation and cellular shape of the organism in response to changes in external light. Genetic and biochemical approaches were employed to accomplish these goals. We observed a number of abundance and protein activity changes that are impacted by red and green light and characterized their specific association with the ability of the organism to increase photosynthesis in response to external light variations. We also identified and characterized genes and proteins involved in determining the shape of the organism in response to light and showed that the organism controls its shape in response to both color and brightness of external light to increase the likelihood of minimizing damage and synthesizing enough energy through photosynthesis to match growth and development to the external light conditions. As RcaE is one of only a few members of the prokaryotic class of phytochrome-related proteins closely linked to a discrete physiological phenomenon, elucidation of the RcaE regulatory gene network that controls growth and development in response to light is providing insight into the mechanisms of operation of biliprotein-regulated light-dependent changes in growth and development more generally in photosynthetic systems, including plants which serve the bases for providing food and fuel. Broader Impacts: In addition to the training of graduate students and postdoctoral scholars, broader impacts of the research included an influence on undergraduate science majors and students from underrepresented groups, including women and participants in undergraduate research support and research programs to promote the integration and success of students of color at Michigan State University. A training component of the research facilitated the development of the ability of these students to think analytically, critically, and independently. This career development plan also included the utilization of instructional methods that enhance students' critical thinking skills, scientific literacy, and technical proficiency.
