U106141.pdf (9.5 MB)
Analysis of phytochrome function in the genus Nicotiana using mutant and transgenic plants
thesisposted on 2014-12-15, 10:33 authored by Matthew Eric. Hudson
Two allelic mutants of Nicotiana plumbaginifolia have bee isolated, which display a hypocotyl which is long (hlg) when seedlings are grown in continuous white light. This can be accounted for by the decreased response of hypocotyl elongation rate in these mutants to red light. Both mutants are deficient in a phyB-like polypeptide that is immuno-detectable in the wild type; both have wild-type levels of a phyA-like polypeptide. These alleles are inherited in a partially dominant manner, and correspond to single base missense mutations in a gene highly homologous to N. tabacum PHYB, which codes for a phytochrome-B-type photoreceptor. When grown in white light, mature hlg mutants are not elongated with respect to the wild type; they also bolt and flower later. The shade-avoidance responses appear intact in these mutants.;The sensitivity of the Nicotiana plumbaginifolia wild type and hlg mutants to photoperiod were investigated. It was found that the hlg mutant shows later bolting than the wild type under long days, but not under short days. The endogenous rosette-leaf-movement rhythms of the mutants display a much greater amplitude than those of the wild type under long-day conditions, but the two behave indistinguishably under short-day conditions.;The Nicotiana plumbaginifolia pew mutants, which are deficient in phytochrome chromophore, were also investigated. They show diminished sensitivity to both red and far-red light, and flower at an earlier stage. The pew3 mutant may belong to a previously uncharacterised class of phytochrome chromophore mutants.;Finally, tobacco plants were created which overexpress the native PHYA gene under the control of the 35S and native PHYA promoters. Both sets of transgenic plants displayed enhanced far-red sensitivity, and were dwarfed as light-grown adults. However, the reversed shade-avoidance effect characteristic of Avena phyA overexpressers was not seen. The plants overexpressing native PHYA were all delayed in flowering.
Date of award1997-01-01
Awarding institutionUniversity of Leicester