| Description: | The role of carotenoids in plant biology is well-established, as is their importance to human health. While much has been learned about the molecular biology of the genes encoding enzymes of carotenoid biosynthesis in plants, we still lack a clear understanding of the regulatory factors that modulate the process of carotenogenesis. Further insight into the identity of such factors should reveal strategies for modifying carotenoid content and composition in crops. This would be invaluable for reducing the incidence of human health problems such as vitamin A deficiency that are, to a significant extent, caused by a reliance on staple crops that are poor sources of carotenoids. To gain a better understanding of the regulation of carotenogenesis, we are characterizing the semi-dominant Or gene of cauliflower (Brassica oleracea). This gene causes various non-photosynthetic tissues to accumulate up to 500 times more beta-carotene than is normally found in comparable tissues of wildtype plants, thus turning them orange. We have been unable to associate the Or gene with any particular gene of either the non-mevalonate pathway or of carotenoid biosynthesis. Given that large microarrays for most plant species will not be forthcoming in the immediate future, plant biologists must seek to explore such resources in related species. We expect Arabidopsis microarrays to be useful for gene discovery in related species such as the ecomomically important Brassica species. We propose to use Arabidopsis microarrays to examine global gene expression in tissues of Or vs. wildtype cauliflower. Comparable probe RNA shall be isolated from the periphery of expanding curd tissue (the edible part), where beta-carotene deposition is particularly significant in Or plants, and virtually absent in wildtype. We will isolate RNA from our standard experimental line that is homozygous for the Or gene, and the parent cultivar from which it arose, Extra Early Snowball, or another related cultivar. We expect that this experiment will identify transcripts whose expression is significantly altered in the Or homozygous line, thus identifying candidate genes for further studies and uncovering concerted shifts in gene expression patterns that may reveal a mode of action for Or. Furthermore, this experiment will serve as a benchmark for evaluating the utility of species-specific microarrays as a tool for gene discovery in related species. |
NASCArrays Information at The BAR
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