Honours Thesis Proposal.
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Below is a proposal that I have submitted for my honours thesis for the 2000-2001 fall/winter terms. But first, some background information. Essentially I will use a combination of genetics, molecular biology, and cell biology to study self-incompatibility in a homostylous mutant from a distylous species (genus: Turnera; family: Turneraceae). A "style" is a structure in a flower that contains stigmas which have receptors for pollen. Thus, a "distylous" species is defined as one that has two different lengths of styles (i.e. short and long). The anthers in this type of species are also present as different lengths (i.e. short anthers in long-styled plants, and long anthers in short-styled plants). These different morphs are associated with a self-incompatibility response (i.e. shorts can cross with longs, and longs with shorts, but shorts can not cross with shorts nor can longs cross with longs). Pollen that is transferred to a style germinates and form "pollen tubes", which grow down the style and eventually reach the ovules for fertilization. Fertilization, however, may be inhibited at any of several steps through the self-incompatibility response in order to promote outcrossing (or to prevent inbreeding) -- for example, by inhibiting pollen tube growth. My due date for the written component is in April of 2001, and I'll have to defend my thesis some short time after that. Until then, I won't include anything more about my thesis except for the proposal shown below.
The inheritance of self-compatibility, homostyly, and a style-specific polygalacturonase I will investigate the inheritance patterns of a self-compatible mutant homostyle that arose as a spontaneous somatic mutation from an otherwise short-styled plant. The mutant has been crossed to a number of long- and short- styled plants. I will study the occurrence of self-compatibility in long-, short- and homostyled progeny from these crosses. Controlled pollinations will be performed, and styles will be fixed and stained with aniline blue. Fluorescence microscopy will be used to determine whether pollen tubes have reached the base of the styles (i.e. are compatible) or have not (i.e. incompatible). Using these data, I will test the recombinant hypothesis for the origin of this self-compatible mutant. I will also investigate whether a short-styled specific polygalacturonase is responsible for self-incompatibility. Some of the progeny in the above crosses are unusual in that some of the homostyles have unexpected expression of the polygalacturonase. Using western blotting, I will investigate the presence or absence of the polygalacturonase in styles and determine (as above) whether it is associated with self-incompatibility. An in vitro system for pollen germination will be attempted. If a reliable system can be developed, pollen tube physiology will be investigated through impalement studies and dye microinjection, and/or by the addition of the polygalacturonase to see if it inhibits tube growth in this in vitro system.
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