An Examination of Leaf Morphogenesis In The Moss, Physcomitrella Patens

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dc.contributor.advisorAshton, Neil
dc.contributor.authorBarker, Elizabeth Io
dc.contributor.committeememberWeger, Harold
dc.contributor.committeememberChapco, William
dc.contributor.committeememberDale, Janis
dc.contributor.externalexaminerCover, David
dc.date.accessioned2012-08-30T14:38:35Z
dc.date.available2012-08-30T14:38:35Z
dc.date.issued2011-08
dc.descriptionA Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy in Biology, University of Regina. xix,324 l. : ill.en_US
dc.description.abstractPhyscomitrella patens is a simple model plant belonging to the bryophytes, which diverged from the tracheophytes approximately 500 million years ago. The leaves of the moss are similar in form to vascular plant leaves although leaves evolved independently in the bryophyte and tracheophyte lineages. Close examination of the morphology of Physcomitrella leaves and investigation of the morphogenetic processes that result in the leaf form and of the hormonal and genetic regulation of those processes will elucidate the evolutionary trajectory of moss leaves. Photomicroscopy and measurement of moss leaves were performed to provide detailed descriptions of leaves in strains of Physcomitrella that exhibited normal and aberrant morphology. Low concentrations of two major phytohormones, auxins and cytokinins, were applied to growing moss cultures to investigate their effects on leaf morphogenesis. A bioinformatic analysis of homologues of vascular plant genes that are involved in leaf development was performed to identify candidate genes that may have been co-opted for regulation of leaf morphogenesis during the early course of plant evolution. The transition from the basal leaf form to the adult form is gradual for all of the heteroblastic features of Physcomitrella leaves with the possible exception of the midrib. Low concentrations of exogenous auxin and cytokinin stimulate cell expansion and cell divisions respectively and auxin may be a key regulator of leaf heteroblasty. Homologues of almost all tracheophyte genes that are known to be involved in leaf morphogenesis are present in the Physcomitrella genome. However, few of the ii Physcomitrella homologues exhibit both a high degree of sequence similarity to the vascular plant genes and high levels of expression in leaves. Of these, class I and class II homeodomain-leucine zipper genes are predicted to play key roles in leaf development in the moss. Other genes may have been co-opted to regulate the processes of cell division, cell expansion and adaxialization/abaxialization of the midrib in bryophyte leaves. Preliminary models of auxin-cytokinin activity and of genetic and hormonal regulation of leaf morphogenetic processes in Physcomitrella provide testable hypotheses for further investigation.en_US
dc.description.authorstatusStudenten
dc.description.peerreviewyesen
dc.description.uriA Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy *, University of Regina. *, * p.en
dc.identifier.tcnumberTC-SRU-3530
dc.identifier.thesisurlhttp://ourspace.uregina.ca/bitstream/handle/10294/3530/Barker_Elizabeth_184020055_PhD_BIOL_SPRING2012.pdf
dc.identifier.urihttps://hdl.handle.net/10294/3530
dc.language.isoenen_US
dc.publisherFaculty of Graduate Studies and Research, University of Reginaen_US
dc.subject.lcshPhyscomitrella patens--Morphogenesis
dc.subject.lcshMosses--Morphogenesis
dc.subject.lcshPlant morphogenesis
dc.titleAn Examination of Leaf Morphogenesis In The Moss, Physcomitrella Patensen_US
dc.typeThesisen
thesis.degree.disciplineBiologyen_US
thesis.degree.grantorUniversity of Reginaen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophy (PhD)en_US
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