PT  - JOURNAL ARTICLE
AU  - Hardeep K. Gumber
AU  - Joseph F. McKenna
AU  - Andrea F. Tolmie
AU  - Alexis M. Jalovec
AU  - Andre C. Kartick
AU  - Katja Graumann
AU  - Hank W. Bass
TI  - MLKS2 is an ARM domain and F-actin-associated KASH protein that functions in stomatal complex development and meiotic chromosome segregation
AID  - 10.1101/609594
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 609594
4099  - http://biorxiv.org/content/early/2019/05/13/609594.short
4100  - http://biorxiv.org/content/early/2019/05/13/609594.full
AB  - The linker of nucleoskeleton and cytoskeleton (LINC) complex is an essential multi-protein structure spanning the eukaryotic nuclear envelope. The LINC complex functions to maintain nuclear architecture, positioning, and mobility, along with specialized functions in meiotic prophase and chromosome segregation. Members of the LINC complex were recently identified in maize, an important scientific and agricultural grass species. Here we characterized Maize LINC KASH AtSINE-like2, MLKS2, which encodes a highly conserved SINE-group plant KASH protein with characteristic N-terminal armadillo repeats (ARM). Using a heterologous expression system, we showed that actively expressed GFP-MLKS2 is targeted to the nuclear periphery and colocalizes with F-actin and the endoplasmic reticulum, but not microtubules in the cell cortex. Expression of GFP-MLKS2, but not GFP-MLKS2ΔARM, resulted in nuclear anchoring. Genetic analysis of transposon-insertion mutations, mlks2-1 and mlks2-2, showed that the mutant phenotypes were pleiotropic, affecting root hair nuclear morphology, stomatal complex development, multiple aspects of meiosis, and pollen viability. In male meiosis, the mutants showed defects for bouquet-stage telomere clustering, nuclear repositioning, perinuclear actin accumulation, dispersal of late prophase bivalents, and meiotic chromosome segregation. These findings support a model in which the nucleus is connected to cytoskeletal F-actin through the ARM-domain, predicted alpha solenoid structure of MLKS2. Functional conservation of MLKS2 was demonstrated through genetic rescue of the misshapen nuclear phenotype of an Arabidopsis (triple-WIP) KASH mutant. This study establishes a role for the SINE-type KASH proteins in affecting the dynamic nuclear phenomena required for normal plant growth and fertility.FRAPFluorescence recovery after photobleachingDPIDays post infiltrationODOptical densityMLKS2Maize LINC KASH AtSINE-like2LINCLinker of nucleoskeleton and cytoskeletonNENuclear envelopeINMInner nuclear membraneONMOuter nuclear membrane