Douglas-fir develops a megagametophyte regardless of the pollination state of the ovule, whereas many other conifers develop a megagametophye in response to polli- nation. Megagametophytes in unfertilized ovules degrade two weeks following fertil- ization of the surrounding population. This is mediated by programmed cell death (PCD). Pollinated and unpollinated megagametophytes were dissected from Douglas- fir cones and extracted for RNA, which was then used as input for sequencing. A transcriptome was assembled from this data and expression levels were calculated. The data were fitted to quadratic regressions to produce coexpression groups. There is no clear upregulation of PCD effectors in the unpollinated megagametophyte. Po- tential regulators of megagametophyte fate are present in the data. Some are as- sociated with ABA signalling and proanthocyanadin biosynthesis while others share similarity to known regulators of PCD. Seed development processes are represented in the expression data, which support current knowledge of conifer seed development and provide targets for research. / Graduate / 0369 / 0309 / 0817 / igboyes@gmail.com

The family Megastigmidae (Hymenoptera: Chalcidoidea), one of the hymenopteran parasitoid families, is unique in containing many species with phytophagous larval feeding strategy. A number of species of different genera are seed-feeders and the genus Bortesia is even capable of inducing galls. The family Megastigmidae is found mainly in the Australian region but a few genera/species groups are widespread throughout different areas, mainly in the Oriental and the Holarctic region. The main goal of this study was to map phylogenetic relationships among genera and clarify the following: the overall number of transitions between a parasitoid and a phytophagous way of life, the ancestral feeding strategy of the family, the evolution of feeding strategies in the genus Megastigmus, and the geographical area of origin of the family. The questions were tested based on a phylogeny reconstructed by a state-of-the-art method - sequencing of "Ultra-Conserved Elements (UCEs)" - using 100 specimens of Megastigmidae from 11 out of 12 currently valid genera selected taking into consideration their feeding strategy and biogeographical origin. The final dataset contains 1210 loci (570,000 base pairs in length) and most nodes are supported by bootstrap value 100. The results show that the family can be divided into 3...

Conifer seed-infesting chalcids of the genus Megastigmus (Hymenoptera: Torymidae) are important forest pests. At least one species, M. spermotrophus Wachtl, has been shown to be able to manipulate the seed development of its host, Douglas-fir (Pseudotsuga menziesii) in remarkable ways, such as redirecting unfertilized ovules that would normally abort. The mechanism of host manipulation is currently unknown. Microbial associates and venoms are two potential mechanisms of host manipulation. Microbial associates are emerging as an important player in insect-plant interactions. There is also evidence that venoms may be important in gall-induction by phytophagous wasps. PCR and 16S rRNA pyrosequencing was used to characterize the microbial associates of Megastigmus and transcriptomic sequencing was used to identify putative venoms that were highly expressed in female M. spermotrophus. The common inherited bacterial symbionts Wolbachia and Rickettsia were found to be prevalent among several populations of Megastigmus spp. screened using a targeted PCR approach. A member of the Betaproteobacteria, Ralstonia, was identified as the dominant microbial associate of M. spermotrophus using 16S rRNA pyrosequencing. The transcriptome of M. spermotrophus was assembled de novo and three putative venoms were identified as highly expressed in females. One of these putative venoms, Aspartylglucosaminidase, (AGA) appears to have originated through gene duplication within the Hymenoptera and has been identified as a major venom component of two divergent parasitoid wasps. AGA was identified as a promising candidate for further investigation as a potential mechanism of early host manipulation by M. spermotrophus. / Graduate / 0353 / 0410 / 0715 / apaulson@shaw.ca