Identification And Functional Characterization Of Plant Small Secreted Proteins During Arbuscular Mycorrhizal Symbiosis

Plant small secreted proteins (SSPs) are sequences of 50 – 250 amino acids in size which are transported out of cells to fulfill multiple functions related to plant growth and development and response to various stresses. With the development of more accurate and affordable genome sequencing technology, an increasing number of SSPs have been predicted using diverse computational tools based on machine learning. Although experimentally validated plant SSPs are still limited, some studies have reported that plant SSPs can be induced and involved in mutualistic relationships between plants and microbes. In Chapter I, known SSPs and their functions in various plant species are reviewed. Additionally, current computational tools and experimental methods that have been widely applied to identify plant SSPs are summarized. A new, robust, and integrated pipeline to discover plant SSPs is proposed. Furthermore, strategies for elucidating the biological functions of SSPs in plants are discussed in Chapter I. Chapter II presents predicted SSPs from 60 plant species and elucidates the evolutionary convergence of changes in SSP sequences. Furthermore, the expression of SSPs induced by arbuscular mycorrhizal fungi (AMF) which correspond to the convergent abilityfor different plants to form mutualistic association with AMF are explored. Overall, this study provides insightful ideas to understand functions of plant SSPs that occur during symbiosis between plants and fungi.