Characterization of Negative Regulators of Arabidopsis Trichome Development

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

0091052 Marks The development of hairs, called trichomes, on the leaf surface of Arabidopsis plants is being used as a model to study the control of cell fate and differentiation. The model has both basic and practical attributes. Understanding the basic mechanisms that control cell fate and differentiation in multicellular organisms is a key goal in biological research. Given that the mechanisms that control the cell cycle are similar in plants and non-plants, it is possible that the information obtained in studying trichome development will lead to a better understanding of how other cell types differentiate. The model is of practical importance because the trichomes on many plants form the first line of defense against hostile environmental factors. Many crop plants only have a sparse covering of hairs and the information obtained from this research could lead to new strategies to improve crop plants. In wild type Arabidopsis, leaf trichomes are uniformly spaced over the leaf surface; less than 0.5% of the trichomes develop adjacent to one another. Previous analyses have shown that trichome spacing is not controlled by chance but by a developmentally regulated spacing program. Such analyses indicate that the spacing program involves cell to cell communication that prevents neighboring cells from becoming trichomes. It has been found that the GL1 gene, which is required for trichome initiation, actually inhibits trichome initiation when overexpressed. This inhibition of initiation is not due to co-suppression, as it has been found that 35S::GL1 plants overexpress both GL1 mRNA and protein. It is proposed that overexpression of GL1 results in the production of a leaf-wide lateral inhibition program in which neighboring cells inhibit each other from becoming trichomes. To test this hypothesis, a mutational analysis is being used to identify mutations that can suppress the 35S::GL1 phenotype and increase leaf trichome initiation. One such interesting mutant, called cot, has been extensively characterized. In 35S::GL1 cot plants, many of the cells that surround a trichome enter the trichome pathway. In addition to 35S::GL1 cot, other 35S::GL1 mutants have been identified that can suppress the 35S::GL1 phenotype. These new mutants will be characterized, and the most interesting genes will be targeted for positional cloning. Although the original 35S::GL1 mutant population was isolated from chemically mutagenized seed, to facilitate cloning of subsequently identified mutant genes, a new population of 35S::GL1 mutants is being induced by T-DNA tagging. In addition to the above studies, another gene hypothesized to be a negative regulator will be characterized. This gene, called CPC-like 1 (CPL1), also appears to limit trichome initiation when expressed at high levels. It is predicted that the CPL1 mechanism of inhibition is distinct from the mechanism resulting from GL1 overexpression. This will be tested. Finally, it will be determined if microarray analysis using gene chips can detect genes that are differentially expressed in plants overexpressing either GL1 or CPL1.