ULTRASTRUCTURE, IMMUNOCYTOCHEMISTRY, AND BIOINFORMATICS OF SPORE DEVELOPMENT IN THE MOSS PHYSCOMITRELLA AND THE HORNWORT DENDROCEROS

Spores are single-celled dispersal units surrounded by a wall of the highly resistant biopolymer sporopollenin. All land plants produce spores. Spore development is described in <italic>Physcomitrella patens</italic>, a moss with single-celled spores, and <italic>Dendroceros</italic>, a hornwort with multicellular spores. Correlated light, fluorescence and immuno-electron microscopy localizes callose in the aperture of developing spores in the model moss <italic>Physcomitrella</italic>. Twelve copies of callose synthase genes were annotated bioinformatically and compared with Arabidopsis callose synthase genes. This study identifies a suspect gene involved in moss spore exine development. Unicellular spores of <italic>Dendroceros</italic> following meiosis remain in tetrads, fill the intercapsular space, and are surrounded by a convoluted, homogeneous electron-opaque outer wall and narrow fibrillar inner wall. No precise pattern of cell division leads to multicellular spores of variable shape and cell number. Evolution of precocious endospory in epiphytic hornworts is a means to protect nascent spores while it develops biochemical and structural machinary to withstand drying. To advance knowledge of genetic control of spore wall development, the sequenced genome of <italic>Physcomitrella</italic> is probed using a bioinformatic approach to decipher the evolution of five selected genes putatively involved in spore wall formation. Those encoding for callose synthase provide the most complete results. Callose involvement in spore development is a plesiomorphic feature of land plants. Phylogenomic analysis of callose synthases in land plants with sequenced genomes revealed a single moss callose synthase basal in a clade containing the only <italic>Arabidopsis</italic> callose synthase implicated in exine development of pollen walls as well as two clades of moss specific callose synthase proteins. A predicted protein-protein interactome was constructed to investigate the protein landscape in <italic>Physcomitrella</italic> for proteins involved in sporogenesis. Orthologous genes were identified between <italic>Physcomitrella</italic>and several other species to map orthologous interactions and predict the first bryophyte interactome. The <italic>Physcomitrella</italic> predicted protein-protein interactome contains 41,936 unique interactions for 4062 different proteins, none of which are associated with sporogenesis. Rather the most conserved interactions among proteins were those associated with metabolic processes. The utility of predicted protein interactions to infer biological roles, providing provisional molecular roadmaps is demonstrated to generate hypotheses for experimental approaches.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Campus Only Dissertation

Discipline thesis:degree_discipline

Plant Biology

Year

2012

Author dc:creator

• Schuette, Scott

Contributors dc:contributor

• Renzaglia, Karen
• Geisler, Matt

• Callose synthase
• Endospory
• Phylogenomic
• Physcomitrella patens
• Predicted protein interactome
• Spore development

Repository record dc:identifier

https://opensiuc.lib.siu.edu/dissertations/499

OAI identifier oai:identifier

oai:opensiuc.lib.siu.edu:dissertations-1499