Poster abstracts
Poster number 46 submitted by Anna Newman-Griffis
Identification and characterization of Medicago truncatula LINC complex components with potential functions in root symbioses
Anna Newman-Griffis (Department of Molecular Genetics and Center for RNA Biology, The Ohio State University), Katherine Beigel (Department of Molecular Genetics, The Ohio State University), Iris Meier (Department of Molecular Genetics and Center for RNA Biology, The Ohio State University)
Abstract:
Symbiotic interactions with soil-dwelling microbes are vital for the fitness of many plant species, including leguminous crops such as soybean. Legumes can form symbioses with both rhizobia and arbuscular mycorrhizal fungi (AMF). Observations since the 1950s have implied, but never definitively established, that nuclear movement is involved in the initiation of both these symbioses. Recently, our lab has shown that nuclear envelope (NE)-spanning complexes comprised of outer nuclear membrane KASH proteins and inner nuclear membrane SUN proteins (known as LINC complexes) are involved in nuclear movement and positioning in Arabidopsis thaliana. These proteins interact in the nuclear envelope lumen through the C-terminal tail of KASH proteins and the SUN domain of SUN proteins. Arabidopsis is susceptible neither to rhizobia nor to AMF, so to translate our work on LINC complexes to the study of symbiosis, we must identify analogous proteins in a new model system.
To determine whether plant LINC complexes are involved in nuclear movement in root-microbe symbioses, we have adopted a reverse genetic approach in the model legume Medicago truncatula. Using the bioinformatic tools developed to identify KASH proteins in Arabidopsis, we have identified Medicago genes that encode 9 putative KASH proteins and one putative SUN protein. A bona fide KASH protein must localize to the NE, interact with SUN proteins in a KASH tail- and SUN domain-dependent manner, and require SUN interaction for NE localization. To validate the putative KASH proteins, we have performed localization and co-immunoprecipitation experiments designed to establish whether they satisfy these criteria. Thus far we have shown that 6 KASH proteins and the SUN protein localize to the NE in Nicotiana benthamiana leaf epidermal cells. All 6 KASH proteins interact with Arabidopsis SUN in a SUN domain-dependent manner in co-immunoprecipitation experiments. Furthermore, two of the six have been shown to depend upon their KASH tails to localize properly and bind Arabidopsis SUN. We are continuing our analysis on the SUN protein and remaining KASH proteins. Our data suggest that the Medicago genome encodes bona fide KASH and SUN proteins, and that these proteins can function as part of a LINC complex in planta.
Keywords: Plant Biology, Symbiosis, Cell Biology