Necrotrophic pathogens are fungal and bacterial species that cause diseases by inducing cell death (necrosis) in their plant hosts. In this project, the molecular and cellular mechanisms that regulate host response to necrotrophic pathogens will be studied. The Botrytis-induced kinase (BIK1) gene of Arabidopsis was identified as an important regulator of plant defense responses. Plants lacking BIK1 show increase susceptibility to necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola but show increased resistance to the bacterial pathogen Pseudomonas syringae. These findings suggest that BIK1 controls defense responses to biotrophic and necrotrophic pathogens culminating in distinct responses, making BIK1 an ideal target for investigating the interactions between defense pathways. Antagonistic interactions between defense pathways mediating resistance to biotrophic and necrotrophic pathogens have been established. However, the molecular mechanisms and the genetic control of these antagonistic interactions are still poorly understood. By studying BIK1 function and its signaling intermediates, this project provides new knowledge on cellular factors required to fight infections and how different disease resistance mechanisms interact. The specific objectives in this project are designed to elucidate the functions of BIK1. The genetic interactions between BIK1 and other components of the Arabidopsis defense will be studied to determine the overall role BIK1 in disease resistance. In addition, the components of the BIK1 regulated defense pathway will be identified and their function determined. Knowledge will be generated on plant molecular factors that signal necrotrophic pathogen borne signals and how these signals reach molecular targets to activate or repress disease resistance. This project provides training opportunity at the undergraduate, graduate and post graduate levels to enhance technical skills in the plant sciences. Activities designed to increase public awareness on the role of biotechnology in crop improvement will be presented at community forums. The project will also train students from groups underrepresented in science.
Plants are continually exposed to harsh environmental conditions that affect their productivity. Adverse plant growth conditions as well as plant diseases and pests reduce the quality and quantity of food, feed and fiber that is produced affecting the well-being of societies. To enable them cope with adverse conditions, plant have evolved a range of regulatory proteins that control the activation of coping mechanisms. Plant protein kinases constitute such proteins and are central to the plant’s ability to perceive stress and activate survival mechanisms. This project was focused on understanding the molecular biology of how some members of this protein super family functions to help plants cope with microbial infection in the genetic model plant Arabidopsis and the crop plant tomato. The premise of the projects is that a thorough understanding of the molecular mechanisms will pave the way for designing better plant disease control and environmental stress tolerance strategies to enhance crop productivity. The Arabidopsis Botrytis induced kinases 1 (BIK1) and tomato Protein kinasea 1b (TPK1b) were studied in details. Extensive genetic, molecular, biochemical studies were completed. Overall, a significant progress was made on how BIk1 and TPK1b contribute to plant disease resistance. Specific amino acid residues that are required for specific functions of these kinases are defined. We have also determined the role of phosphorylation for the function of BIK1 and TPK1b. The functional relationship between BIK1 and other genes contributing plant defense were examined delineating genes that antagonize or promote BIK1 function in defense. Further, we have discovered that BIK1 as well as TPK1b contribute to normal plant growth and development as well as plant defense through their contributions to ethylene signaling. Ethylene is a plant hormone emitted during normal physiological processes to promote growth as well as to activate plant stress and disease tolerance mechanisms. Many genes whose functions depend on BIK1 were identified and studied. These results are published in peer reviewed journals. In addition to the technical aspects of this project, the funding provided by NSF helped train graduate students and post-doctoral associate. Undergraduate students were recruited in the form of summer internships and trained in the fundamentals of research techniques in molecular biology and genetics. The goal was encourage students, through this research experience, to purse graduate educations. Indeed, some of the summer interns went on to join graduate schools at various institutions.
