Poster abstracts
Poster number 29 submitted by Lily Schumacher
Characterizing force transfer across Arabidopsis LINC complexes
Lily A. Schumacher (Biophysics Graduate Program), Norman R. Groves (Department of Molecular Genetics, The Ohio State University), Bronson Frank (Department of Biomedical Engineering, The Ohio State University), Daniel E. Conway (Department of Biomedical Engineering, The Ohio State University), Iris Meier (Department of Molecular Genetics, The Ohio State University)
Abstract:
The nucleus is a highly dynamic organelle that moves and changes during development and in response to the environment. For example, nuclear dynamics are critical for neuron and ear hair development in animals, as well as root symbiosis and male fertility in plants. Nuclear dynamics are mediated by Linker ofNucleoskeletonand Cytoskeleton (LINC) complexes, which consist of Sad1/UNC-84 (SUN) proteins and Klarsicht/ANC-1/Syne Homology (KASH) proteins, which span the nuclear envelope. KASH proteinsinterface with the cytoskeleton via their cytoplasmic domains and bindSUN proteins via their KASH domain. In C. elegans, disulfide bonds are required for nuclear anchorage, while a shorter KASH domain is required for nuclear migration. Plant KASH domains are shorter, cannot form disulfide bonds, and have a different C-terminal motif. Two Arabidopsis KASH proteins act in different functional contexts: SINE1 plays a role in stomatal closure, while WIP1 is required for root hair nuclear elongation and nuclear migration in pollen tubes. We hypothesize that individual KASH domains are specific to their LINC complex roles due to different force requirements.
We show that the SINE1 KASH domain isrequiredfor SINE1 function in stomata and the WIP1 KASH domain for WIP1 function intrichoblasts, but that KASH domains are interchangeable for nuclear movement in pollen tubes. Molecular modeling showed that SINE1 has two distinct binding modes depending on its interaction partner, SUN1 or SUN2, while WIP1 binds very similarly to both. To examine whether this differential requirement for specific KASH domains may indicate a different tolerance of SUN-KASH interactions to force, we developed a SINE1 FRET tension sensor. This sensor perceives more force than a force insensitive control and we are examining these force differences in the biologically relevant context. Novel use of KASH tension sensors in plants will establish quantitative biophysical measurements of plant nuclear forces.
Keywords: LINC Complex, FRET, Plant Biology