Carter, Anthony D. (2013) Cell-type specific comparative analysis of lateral root and nodule development at phenotypic and genomic levels. PhD thesis, University of Warwick.

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Abstract

Nodules and lateral roots are both key organs for the uptake of nutrients by
plants. During nodulation, leguminous plants form root nodules, housing symbiotic
Rhizobial bacteria able to fix atmospheric nitrogen, allowing the plant to utilise it.
Lateral roots are formed by all plants and allow the root system to be extended laterally,
increasing the region of soil from which nutrients may be taken up. Formation
of lateral roots and nodules share developmental features such as single cell-type
origins of the primordia, and hormonal and nutrient regulatory mechanisms, so it
is hypothesised that the evolution of nodulation co-opted elements of pre-existing
genetic mechanisms of lateral root formation.
To test this hypothesis, Arabidopsis thaliana (non-legume) genes similar to
known Medicago truncatula (legume) nodulation genes were screened for phenotypic
effects. Mutants of Arabidopsis NODGS and a GRAS-domain SCR-like transcription
factor were found to confer lateral root phenotypes, suggesting evidence for the
co-option hypothesis. The mutants were examined further using cell-type specific
transcriptomics through Fluorescence-Activated Cell Sorting (FACS) to identify genomic
components underlying the possible co-option. For the purposes of future
research, the translation of FACS transcriptomics to Medicago was evaluated, validating
microarray probe design for the most recent genome annotation but also
highlighting challenges faced in analysing more complex plant roots.
The GRAS-domain SCR-like transcription factor mutant was found to modulate
lateral root development through pathways involving the phytohormone gibberellic
acid (GA). Treatment with GA rescued some components of the GRASdomain
SCR-like transcription factor phenotype, indicating a potential role for the
gene in activating GA biosynthesis.
A second mutant, of NODGS, was also found to affect lateral root development
with some dependence on nitrate level. Existing knowledge suggested a role in
root morphogenesis and flagellin-triggered signalling, and this work implies a level
of cell-type specificity in gene function.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QH Natural history > QH426 Genetics Q Science > QK Botany Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	Arabidopsis thaliana -- Genetics, Legumes -- Genetics, Transcription factors, Roots (Botany) -- Formation
Official Date:	May 2013
Dates:	Date Event May 2013 Submitted
Institution:	University of Warwick
Theses Department:	Systems Biology Doctoral Training Centre
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Gifford, Miriam; Burroughs, Nigel John
Extent:	x, 252 leaves : illustrations, charts.
Language:	eng

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