 | | | | | Alternation of generations in land plants; Vegetative phase change in maize | | We have taken an integrative approach to identify genes that control the switching between gametophyte and sporophyte development.
(1) Fern genes responsible for the commitment to the apogamy pathway will be identified. A fern was chosen for this step because both generations are free living in this taxon, providing an experimental advantage, and because ferns are located between bryophytes and seed plants in the land plant phylogeny. We have established an experimental system in which sporophytes generate directly from gametophytes bypassing sexual reproduction (a process called apogamy) in Ceratopteris richardii. The developmental window during which gametophyte tissues are committed to the apogamy pathway well before any morphphological changes can be detected, has been defined. Using this system, a combination of the "suppression subtractive hybridization" cloning method and microarray analysis has been employed to identify genes whose alteration of expression correlates with apogamy commitment.
(2) The homologs of these genes will be sought in the seed plant Arabidopsis and the broyophyte Physcomitrella patens. Both are model plants with nearly all the resources available for this study. This will at once circumvent the drawbacks of ferns (large genome and not transformable) and broaden the scope both up and down the land plant phylogeny.
(3) Functional studies of the genes will be performed. Their temporal and spatial expression will be studied by in situ method in all three species. Knockout mutants of the genes will be sought or be created in Arabidopsis and in P. patens. The phenotypes of these mutants will be studies and compared between the two model plants and, for a subset of these genes, with C. richardii. For those genes whose expression correlates negatively with apogamy commitment, overexpressors will be created and their effects examined.
These results will provide necessary materials and a framework for future study of the biochemical functions and interactions of the gene products in switching from one generation to the other during apogamy and in normal life cycle. It will also form a foundation for future study of the evolution of alternation of generations in land plants.
| | | Selected Publications | | | Cordle, A.R., Irish, E.E., and Cheng, C.-L. (2007). Apogamy induction in Ceratopteris richardii. Int. J. Plant Sci 168: 361-369. | | | Escamilla, L.L.E., Chen, W. Card, M.L., Shih, M.-S., Cheng , C.L., and Poulton, J.E. (2006). Arabidopsis thaliana β-glucosidases BGLU45 and BGLU46 hydrolyse monolignol glucosides. Phytochemistry 67: 1651-1660. | | | Xu, Z., Escamilla, L.L.E., Zheng L., Lalgondar, M., Bevan, D.R., Mohamed, A., Cheng, C.-L., Shih, M.-C., Poulton, J.E., and Esen, A. (2004) Functional genomic analysis of Arabidopsis thaliana glycoside hydrolase family 1. Plant Mol. Biol.55: 343-367. | | | Cao, D., Froehlich, J.E., Zhang, H., and Cheng, C.-L. (2003) A photomorphogenesis defective mutant cr88 encodes a chloroplast Hsp90. Plant J 33: 107-118. | | | Stanislaus M.A. and Cheng, C.-L. (2002) Genetically engineered self-destruction: an alternative to herbicides for cover crop systems. Weed Sci. 50: 794-801. | | | Cao, D., Lin, Y., and Cheng, C.-L. (2000) Genetic interactions between chlorate resistant mutant cr88 and photomorphogenic mutants cop1 and hy5. Plant Cell 12: 199-210. |
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