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Investigation of the genetic and molecular mechanisms patterning leaf morphogenesis

Posted on:2011-05-23Degree:Ph.DType:Dissertation
University:University of California, DavisCandidate:Koenig, Daniel PaulFull Text:PDF
GTID:1443390002465518Subject:Biology
Abstract/Summary:
Leaf shape is one of the most spectacularly diverse morphological features of plants. One of the most common variations in morphology seen amongst leaves is the degree to which the blade is dissected into smaller units. Simple leaves are composed of a single unbroken blade, that may be partially dissected to form lobes or serrations. Compound leaves are further dissected such that distinct blade units are produced termed leaflets. Here, I describe an investigation of the developmental and genetic basis for natural variation in leaf morphology.;The first section focuses on the plant phytohormone auxin and the development of compound leaves in tomato. Auxin is found to be an important patterning signal during early leaf development, delineating the initiation of both leaflets and blade. This is accomplished by active transport of auxin by the tomato PIN1 protein to the sites of lateral growth in leaves. The repression of growth between leaflets is accomplished by the activity of the tomato AUX/IAA gene ENTIRE. These results reveal a simple mechanism by which compound leaf patterning can be accomplished. The tomato JAGGED otholog, LYRATE, acts within the context of this auxin model to promote cell division.;The second part deals with natural variation in leaf complexity between wild tomato species. Several QTL mapping experiments are presented that identify a large number of genetic loci that control natural variation in leaf complexity. Interesting parallel morphological alterations appear to have utilized a major locus on the long arm of chromosome 6. This work lead to the cloning of one of these QTL, Pts, that is responsible for variation between Galapagean tomato species. PTS is a member of a novel class of KNOX genes which act by influencing the interactions between the canonical KNOX transcription factors and the BEL-like transcription factors. Also described is the identification of the tomato classical mutant bipinnata which encodes one such BEL-like gene, and phenocopies the Pts mutant. Mutations in this pathway might be selected over evolutionary time because they lack pleiotropic effects.
Keywords/Search Tags:Leaf, PTS, Genetic, Patterning, Variation
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