Item – Theses Canada

OCLC number
Kyriakopoulou, Garyfallia,1965-
Molecular cloning of three different Achlya ambisexualis hsp70 cDNAs, and changes in the accumulation of hsp70 transcript populations during hyphal branching.
Ph. D. -- University of Toronto, 1998
Ottawa :National Library of Canada = Bibliothèque nationale du Canada,[1999]
4 microfiches.
Includes bibliographical references.
In the filamentous fungus 'Achlya ambisexualis' sexual differentiation is regulated by a set of steroid hormones. During vegetative growth, the hyphae of the organism appear smooth with occasional large branches. In response to the 'Achlya' steroid hormone antheridiol, numerous specialized lateral branches form that subsequently differentiate into gamete bearing structures. Hormone-induced branching is accompanied by changes in a number of transcript populations encoding different HSP70 heat shock proteins. Using both homologous and heterologous hsp70 probes, three different ' A. ambisexualis' hsp70 cDNAs were cloned and characterized. Analyses of the predicted amino acid sequences suggested that these cDNAs, encoded respectively: a cytoplasmic HSP70 protein, an endoplasmic reticulum HSP70 protein and a novel HSP70 protein; This latter HSP70 has a unique N-terminal extension that does not conform to known targetting motifs. The level of the hsp70 transcript population represented detected by this latter hsp70 cDNA was increased when cell cultures were depleted of glucose or treated with agents such as tunicamycin or calcium ionophore A23187. The above treatments have been reported to regulate hsp70 genes that encode proteins localized to the endoplasmic reticulum, or mitochondria. However, the HSP70 protein encoded by these transcripts has a unique N-terminal extension that does not conform to known organelle targetting signals and the ultimate cell location of this protein is not known as yet. The level of each of the three HSP70 transcript populations is altered during branching and differentiation by the hormone antheridiol. Similar changes in the levels of these populations were observed when hyphae underwent vegetative branching i.e. branching not related to sexual differentiation. These results suggest that common morphogenetic events take place during branching in both vegetative and sexually differentiating mycelia and that these events appear to require HSP70 chaperones.