Understanding plant cell lipid signaling is critical for understanding the regulation of many aspects of plant physiology. Phosphoinositides (PIs) play critical roles in plant responses to stress, vascular development, guard cell dynamics and cell growth and morphology. Plants have evolved novel mechanisms of PI signaling and novel PI modifying pathways that are distinct from those in animals and yeast. Studies undertaken in this project will lead to new insights into the function of PIs in plants cells and new tools and methods that will greatly enhance study of plant PI signaling, and ultimately lead to the development of novel approaches for engineering plants with greater tolerances to abiotic and biotic stresses.
Primarily through their interactions with proteins, PIs regulate functions including vesicle trafficking and membrane/cytoskeleton interactions. PI accumulation is regulated in part by the action of PI phosphatases, including the Sac-domain proteins. Sac-domain proteins are conserved across eukaryotes, but a novel distinct family member, SAC9, is found only in plants and green algae. Plant and algal SAC9 proteins have many conserved differences from the other Sac-domain proteins, including the other Sac-domain proteins found in plants. Dr. Williams's group's initial studies have demonstrated that SAC9 is important for regulation of both PtdIns(4,5)P2 levels and actin cytoskeleton distribution in plants. Further characterization of the novel SAC9 protein, and phenotypes of sac9 mutant plants, will both inform studies on Sac-domain proteins across eukaryotes, and contribute to an understanding of the interactions between PIs, the actin cytoskeleton and plant cell functions. This project will (1) characterize the activity and cellular localization of AtSAC9 through in vitro and in vivo expression; (2) characterize the roles of the plant-specific C-terminal domain and SAC9-specific WW domain in AtSAC9 function and cellular distribution; (3) examine SAC9 function in vivo through transient and inducible expression studies; and (4) test our model of SAC9 function by examining co-localization of SAC9, PtdIns(4,5)P2 and actin filaments using fluorescent proteins and immunolocalization.
Broader Impact Both principal investigators have extensive experience and demonstrated success conducting research with undergraduates, and believe that providing exciting research opportunities to undergraduates in the classroom and the research lab is instrumental for bringing them into the science pipeline. Drs. Williams and Dewald have developed ways that ensure the undergraduates in their laboratories will be trained technically in sophisticated approaches and will participate in research design and execution. The research will be carried out principally by undergraduate students at both Harvey Mudd College (HMC) and Utah State University (USU). One graduate student at USU will collaborate with the undergraduates and participate in undergraduate teaching. This project builds on an ongoing and successful collaboration that has involved undergraduates at both HMC and USU.
