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Title: Quantitative characterisation of root tip regeneration and tropism in external electric field
Author: Kral, Nicolas
ISNI:       0000 0004 8504 5872
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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We studied two phenomena specific to the root of the Arabidopsis, the effect of weak external electric field on root tip regeneration and root growth. We constructed and validated three experimental tools V-tank, V-box and V-slide that allowed us to subject roots to electric fields, with various imaging capabilities. We observed an increase in root regeneration frequency caused by application of 2.5V/cm weak external electric field. In addition, we observed change in the distribution of auxin and a decreased number of cell divisions in the remaining root stump shortly after electric field treatment. In addition to regenerating roots, we also studied the perturbation caused by electric field in the growing roots of Arabidopsis. Arabidopsis root tip showed electrotropic bend towards cathode in response to external electric field, which we described quantitatively. After testing six different media, our data suggests 0.1-1mA conductance of the media leads to the most dramatic root electrotropism. The data showed asymmetric cell expansion during root electrotropism, suggesting cellular mechanism of root turn. We found out gravitropism and electrotropism does not share the same molecular mechanism. Our data confirmed that functional glr3.4 gene coding for a Ca2 ion channel is necessary for wild type electrotropism, in addition further seven ion channel genes were identified to be potentially necessary for root electrotropism. Membrane depolarisations in root cells were attempted to be observed with fluorescent Voltage Sensitive Dyes. The data showed that membrane depolarisations prior electric field exposure inhibited growing root from responding with electrotropic turn, suggesting the role of membrane voltage maintenance in electrotropism. The observations showed electric field can perturb root regeneration and root growth. The mechanism behind increase in root regeneration frequency is unknown. The mechanism of root electrotropism seen in a growing root is separate to that of gravitropism and it involves Ca2+ channel GLR3.4 and membrane depolarisations.
Supervisor: Sena, Giovanni ; Turnbull, Colin ; Dunsby, Chris Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral