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UBC Theses and Dissertations

Molecular phenotyping of cell wall development in the Arabidopsis thaliana primary stem Hall, Hardy Craig


Plant cell walls are sophisticated, dynamic structures that play a vital role in coordinating the directional growth of plant tissues. The rapid elongation of the inflorescence stem in the model plant Arabidopsis thaliana is accompanied by radical changes in cell wall structure and chemistry, but the study of the underlying mechanisms has been hampered by difficulties in sampling discrete developmental states along the developing stem. I have created a novel sampling approach that allows me to sample stem tissues representing specific and distinct developmental phases (elongation rate increase, maximum growth rate, and growth cessation) from individual plants, by use of time-lapse imagery and computational analysis of growth kinematic profiles. This high-resolution growth context enables the harvest of pooled, developmentally-matched samples that I then used for transcriptome profiling of growth-characterized stem segments, and for immunohistochemical analysis of growth-associated cell wall epitopes in specific cell types within stem crosssections. The resulting transcript profiles have identified dozens of genes, both known and novel, whose expression is coupled to these growth transitions. Unique cell typespecific epitope patterns were observed during the most rapid phase of elongation, providing evidence for structural divergence of cell walls among these cell types despite a common developmental environment of diffuse elongation. This study has thus produced two global perspectives of the cellular events accompanying the transition from early differentiation through maximum anisotropic cell expansion to growth cessation and secondary cell wall maturation, in a single organ. The results collectively provide important hypothesis-generating insights anchored to a precise developmental scaffold of cell wall differentiation established through growth kinematic profiling.

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