Triacylglycerol (TAG) production in the microspore derived (MD) cell suspension culture ofBrassica napus L. cv Jet Neuf was enhanced when the sucrose concentration in the growth medium was increased from 2 to 14 % (w/v). mRNA differential display by polymerase chain reaction was used to examine gene expression in cells grown at different sucrose concentrations in order to identify mRNAs which could be associated with oil formation. The anchored primer, T12AA, was used to screen one subset, representing approximately one twelfth of the transcript population, isolated from cultures grown in media supplemented to 2, 6 and 14 % (w/v) sucrose. Analysis of this mRNA subset revealed thirteen cDNAs which appeared to be upregulated as the sucrose concentration was increased. Cloning and sequencing revealed multiple cDNA fragments for each signal detected by differential display. RT-PCR analysis of sixteen different cDNAs revealed that eight encoded mRNAs which were upregulated in parallel to the increase in media sucrose. Comparison of the eight upregulated cDNAs to other sequences in GenBank revealed the following: (1) BSS8A had a 100% identity with the last 25 amino acids of an acyl carrier protein from Arabidopsis thaliana, (2) BSS1A displayed homology to a number of sequences of unknown function, (3) BSS1 IB displayed weak but significant homology to a number of sequences of unknown function, (4) BSS13A displayed homology to four members of the thioredoxin family from ,4. thaliana and (5) four Had no significant homology to previously reported sequences which makes them potential candidates to encode lipogenic enzymes. These results indicate that differential display of mRNA may be a simple and rapid method for the identification of sucrose-modulated gene expression changes in this system and for the characterization of novel sequences potentially encoding lipogenic proteins. / xxi, 256 leaves : ill. ; 28 cm.

This study investigated whether participation in the Partnership for Research and Education in Plants (PREP), a long-term authentic plant research project, in conjunction with explicit verses implicit instruction can change high school students' conceptions of the nature of science (NOS). The participants included a total of 134 students comprised of three groups from 10 total classes over the course of two academic years. Participants in four classes (two each year) participated in PREP and received explicit instruction on NOS. Participants in four other classes (two each year) participated in PREP and received implicit only instruction on NOS. Additionally, two classes (one each year) of high-achieving freshmen participated in PREP and received explicit instruction on NOS. This third group was used as a comparative group to the other two groups, due to their high achievement in middle school math and science. The treatment for all three groups spanned 8 weeks and included participation in an authentic plant research project. An open-ended questionnaire (modified Views of Nature of Science - VNOS), in conjunction with semi-structured interviews, was used to assess students' conceptions before and after the intervention. Results showed that all three groups improved their conceptions of NOS equally. The high-achieving group began with significantly higher-scoring views prior to the completion of the intervention, and improved to the same degree as the other two groups. A comparison of the explicit group to the implicit only group showed that there was no significant difference in their improvement, as both groups improved equally. Implications for the teaching and learning of NOS are discussed.

Diacylglycerol acyltransferase (DGAT), an integral membrane protein of the endoplasmic reticulum, catalyses the final step in the sn-glycerol-3-phosphate pathway leading to triacylglycerol. Although DGAT has been cloned from a variety of species, including the major oilseed crop of Canada, canola (Brassica napus), little is known about the structure/function of the enzyme. BnDGAT1 is the major isoform of type I DGAT (DGAT-I) in microspore-derived cell suspension cultures of B. napus L. cv Jet Neuf, with the possible existence of a truncated form of BnDGAT1 known as BnDGAT2. In order to gain some insight into the topology of the enzyme, type I DGAT from B. napus was investigated using two approaches: (1) in vitro translation in the presence of microsomes and (2) immunochemical analyses of microsomes isolated from cell suspension cultures, both in combination with proteolytic mapping. Difficulties were encountered with the in vitro translation approach, possibly due to proper incorporation of the polypeptide into microsomal vesicles. Two cytocolic regions were identified in BnDGAT1, and one cytosolic region in putative BnDGAT2, using the immunochemical approach, thus providing some insight into the topology of B. napus DGAT-I. The results here support and nine and eight membrane-spanning topology for BnDGAT1 and BnGAT2, respectively. / xvii, 194 leaves ; 29 cm.

M.Sc. (Zoology) / Please refer to full text to view abstract