Crwn Family Proteins Regulate Nuclear Organization And Nuclear Function In Arabidopsis Thaliana
CRWN FAMILY PROTEINS REGULATE NUCLEAR ORGANIZATION AND NUCLEAR FUNCTION IN ARABIDOPSIS THALIANA Haiyi Wang Ph. D. Cornell University  : The molecular components and processes that shape and organize nuclei in plant cells are poorly understood. This thesis describes genetic, cytological, and biochemical studies of CRWN (CROWDED NUCLEI) proteins, which are required for proper nuclear structure in the flowering plant, Arabidopsis thaliana. These plant-specific proteins feature a long coiled-coil motif, with a conserved C-terminal domain. CRWN proteins are expressed primarily in proliferating tissues, and are located at the nuclear periphery. CRWN1 and CRWN4 belong to a nuclear fraction resistant to high salt and mild detergent extraction. I hypothesize that CRWN proteins are structural components of plant nuclei. Genetic analysis of the whole family of crwn mutants in Arabidopsis thaliana revealed a variety of phenotypic changes, including altered nuclear shape, reduced nuclear size, and heterochromatin aggregation or dispersion, mildly decreased endopolyploidy levels, and increased nuclear DNA density. In addition, some crwn mutants were dwarfed with early flowering times, shorter internodes, heavier branches, and delayed senescence. A subsequent mRNA-seq profiling in representative crwn mutants illustrated genome-wide transcriptional mis-regulation, and identified candidate genes responsible for phenotypic changes in crwn mutants. I propose that the loss of CRWN proteins primarily alters nuclear organization, leading to alterations in gene expression. Phylogenetic analysis partitioned this protein family into CRWN1-like and CRWN4like sub-categories, and non-redundant morphological alterations observed in crwn1 versus crwn4 mutants further support this idea. Nonetheless, the transcriptomic data uncovered shared profiles of mis-expressed loci regulated by CRWN1-like and CRWN4-like genes. Moreover, regulatory relationships among CRWN paralogs exist on both the mRNA and protein level. A physical interaction between CRWN1 and CRWN4 proteins was demonstrated by immunoprecipitation experiments. These findings suggest that different CRWN proteins function together to maintain nuclear organization in plants.
CRWN; nuclear organization; epigenetics
Richards, Eric Jean
Nasrallah, June Bowman; Liu, Jun; Pawlowski, Wojciech
Ph. D., Plant Biology
Doctor of Philosophy
dissertation or thesis