Unraveling the molecular photobiology of the emerging model fern, Ceratopteris richardii.
Item
-
Title
-
Unraveling the molecular photobiology of the emerging model fern, Ceratopteris richardii.
-
Identifier
-
AAI3187403
-
identifier
-
3187403
-
Creator
-
Bissoondial, Terrence Young.
-
Contributor
-
Adviser: Timothy Short
-
Date
-
2005
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Biology, Molecular | Biology, Cell
-
Abstract
-
A plant's survival depends on its ability to detect and react to light-mediated changes in its environment. One type of photoreceptors that enables a plant to modify its development and structure in response to light is the red light and far-red light photoreceptors, the phytochromes. Although many functions of phytochrome in mosses and angiosperms have been molecularly characterized, the molecular biology of phytochromes in ferns and gymnosperms are obscured by their relatively long lifecycles and the lack of available tools to knockout or knockdown specific target genes. Ceratopteris richardii is a recently evolved polypod that is emerging as a model fern to study the process of photomorphogenesis because of its rapid lifecycle and the ability to reduce the expression of targeted genes in dry spores by RNA interference (RNAi). Previous physiological studies of photomorphogenesis in Ceratopteris richardii have provided circumstantial evidence that phytochromes and cryptochromes (blue light photoreceptors) are involved in the regulation of spore germination and gametophyte development, although no photoreceptors have been molecularly identified. In this study, five phytochrome sequences have been isolated: CrPHY1A, CrPHY1B (partial cDNA), CrPHY2, CrPHY4A and CrPHY4B. CrPHY1B and CrPHY4A have resulted from recent duplications, possibly by retro-transposition and gene conversion or homologous recombination. Phylogenetic analyses show that the PHY1 and PHY2 genes of ferns evolved very early in the history of vascular plant, and that their divergence preceded the separation of ferns from seed plants. During the evolution of the leptosporangiate ferns, a gene duplication occurred coinciding with angiosperm radiation (approximately 260 mya), producing the orthologues PHY2 and PHY4 . Consistent with the phylogenetic analyses, physiological studies demonstrate that the responses mediated by the phytochromes of ferns show limited similarities to those of the phyA and the phyB of angiosperms. The phytochrome multigene family of Ceratopteris richardii act synergistically (perhaps redundantly) and the absolute dosage of the Pfr form of phytochrome regulates germination, cell division, rhizoid formation and chlorophyll production. Gene duplication of phytochromes in ferns and positive selection may have allowed some group of ferns to attain their current diversity as a response to the diversification of flowering plants. Further physiological and molecular studies have also shown that specific cryptochromes (e.g. CrCRY4) act antagonistically to phytochromes to regulate germination and prothallar development, while others may act synergistically with phytochromes to allow for greater development in specific light conditions.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
