Intellectual merit. Red and blue light regulate seedling de-etiolation and stomatal aperture in natural environments. The signal transduction cascades that link the perception of light to the de-etiolation and stomatal opening responses are still largely unknown, and hypersensitive to red and blue (hrb) mutants are of particular interest. The hrb mutants were initially isolated for their short hypocotyl phenotype under red and blue light. The hrb mutants are also more resistant to dehydration and show reduced water loss and blue light-regulated stomatal aperture. The HRB1 gene has been cloned and the hrb2 and hrb3 mutations have been mapped to chromosomes 2 and 4, respectively. HRB1 is a nuclear ZZ-type zinc finger protein and physically interacts with phosphatase 7 or PP7, a previously identified positive regulator of blue light signaling in the nucleus. HRB1 is phosphorylated in vivo and is involved in a protein complex mostly in its de-phosphorylated form. The goal of this project is to study the function of HRB1 and PP7 and their interaction in the control of de-etiolation and stomatal aperture under blue light. The studies on these genetic and biochemical interactions will bring novel insights into HRB1 function and the network structure of the light signaling machinery.
Broader impacts. This research will provide opportunities for undergraduates, graduate students, and postdoctoral fellows to gain significant research experiences and to develop their ability to critically analyze and solve scientific problems. A diverse group of undergraduates will include African Americans and Hispanics drawn from academic courses and from a campus-wide life science summer undergraduate research program. A specific training plan has been designed for the undergraduates, ranging from physiological, genetic, to molecular studies. This project will also support undergraduate education through seminars at small and research-limited undergraduate institutions and recruitment of students at these institutions to perform summer research at the University of Minnesota. On an even broader level, the proposed studies will open new possibilities to engineer plants to survive desiccation by controlling stomatal function and hence CO2 uptake and the loss of water through transpiration.
The intellectual merit of the work Stomatal pores are situated in the leaf epidermis to allow CO2 uptake and the loss of water through transpiration. The pore apertures are regulated by blue and red light. The signal transduction cascades that link the perception of light signals to stomatal opening responses are still largely unknown. We identified three Arabidopsis hypersensitive to red and blue or hrb mutants on the basis of their short hypocotyl phenotype. The three mutants also showed reduced water loss and stomatal aperture under blue light. The goals of this project are to study the interaction between two light signaling components, HRB1 and PP7, in the control of stomatal aperture under blue light. We have investigated the in vivo interaction of HRB1 with PP7 through pull-down and co-localization or FRET assays, and the genetic interaction of HRB1 with PP7. We have also studied the biological consequence of HRB1 and PP7 interaction, the influence of light and PP7 on the association of HRB1 with a protein complex, and the HRB1-containing protein complex. We published two research articles and one review article, with one graduate student as the leading author in 2011 and 2012. Our studies on the proposed genetic and biochemical interactions of the two key players will bring novel insights into their function and the network structure of the light signaling machinery. HRB1 belongs to a ZZ-type zinc finger protein family and PP7 belongs to 2C-type phosphatases. The studies on the function of HRB1 and PP7 and their interaction would greatly enhance our understanding on their homologs in many other organisms including humans. The broader impacts of the work This project brings researchers at different stages of their career development, including undergraduates, graduate students, postdoctoral associate, and research scientist. This grant provided opportunities for us to mentor graduate students as our next-generation scientists and provided the exposure of undergraduates to science and technology. They performed various physiological, genetic, and biochemical experiments, gained significant experiences in molecular biology, and developed their ability to critically analyze and solve scientific problems. The postdoctoral associate and the graduate student vigorously presented their research results in national conferences and regular lab meeting or journal club. They actively participated in in our plant biological science graduate program seminar series, and delivered a few lectures in PBS 5412 plant physiology, one of the courses that I taught. To actively engage in undergraduate education, I recruited a junior, Honglin Li, to our lab as an undergraduate researcher in regular semesters since 2012. We have designed a specific training plan for her and she has been ever since involved in various physiological and molecular experiments. We also trained another undergraduate student, Hannah Spaulding, from Luther College in the summer of 2012, and Milton Torres, from University of Puerto Rica in the summer of 2013. Our discovery on the role of HRB1 and HRB2 in the control of stomatal aperture would largely impact agricultural practice and bioengineering of our future crops.
