Most metazoans contain nuclear proteins called lamins that are, in part, responsible for the structural organization of the nucleus. These proteins contain a central coiled-coiled domain that is flanked by globular N- and C-terminal domains. Lamins line the interior of the nuclear envelope forming a scaffolding meshwork. These proteins function to maintain nuclear integrity, chomosome organization and have been implicated in several human diseases. Surprisingly, in plants, no direct sequence homologs of lamins have been found. However, a potential structural analog of lamins was discovered in Daucus carota called NMCP (Nuclear Matrix Constituent Protein). In Carrot, NMCP was shown to localize exclusively at nucleoplasm side of the nuclear envelope. Even though, NMCP is not a sequence homolog it shares the same tripartite structure of lamins and nuclear localization. Since structure is strongly related to function, the NMCP proteins are a good candidate for lamin proteins in plants. Four NMCP genes exist in the flowering plant Arabidopsis thaliana and in previous research, the NMCP1,2 double mutant (nmcp1-1 nmcp2-1) was shown to display a dwarf phenotype and reduced nuclear size. The NMCP genes are therefore important for nuclear structure and morphology of plants and are of much scientific interest.
The main focus of my project was to further characterize the role of the Arabidopsis NMCP proteins on nuclear size and structure. Because genetic redundancy poses a problem in the study of the NMCP genes may, I set out to construct and characterize triple mutant combinations. One such triple mutant nmcp1-1 nmcp3-1 nmcp4-1 was severely dwarfed at the whole plant level and had reduced fertility. This triple mutant also had reduced nuclear size. These results advance idea that the NMCP proteins are important for normal nuclear structure and organization in plants.
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Natural Sciences Learning Center
Washington University - Biology
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