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Molecular and physiological studies of Pisum mutants

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Batge, SL (2000) Molecular and physiological studies of Pisum mutants. PhD thesis, University of Tasmania.

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Abstract

The characterisation of developmental mutants generates insights into plant
growth processes. This thesis presents a molecular investigation of three
phytochrome A mutants of Pisum sativum L. (garden pea), and a study of the
influence of abscisic acid (ABA) on seed development in the gibberellin (GA)-
deficient mutant lh-2.
Phytochromes are plant biliproteins which sense red (R, 600 - 700 nm) and far-red
(FR, 700 - 760 nm) light and act in concert with other photoreceptors to influence
developmental processes, such as germination, seedling de-etiolation, daylength
perception and transition to flowering, in response to environmental cues. Two
allelic mutants at the funl locus are deficient in phytochrome A. Point mutations
have now been identified within the PHYA structural gene of both fun1-1 and
fun1-2. These cause premature stop codons, predicted to result in production of a
truncated and inactive phytochrome A protein in the mutant plants. This is
consistent with the demonstration that fun1-2 plants lack immunodetectable
PHYA, and with the previously described phenotypes. Co-segregation between
the fun1-2 mutant phenotype and the identified molecular lesion confirms that the
funl mutant phenotype is the direct result of disruption to the PHYA structural
gene. The funl mutants can now be used confidently in future rigorous analyses
of the physiological and developmental roles of the phytochrome family in pea.
The AF05 mutant phenotype is similar to that described for transgenic
phytochrome A-overexpressing lines in other species. Results presented in this
thesis indicate that there is no mutation in the PHYA gene of this mutant, either in
the coding region or promoter. Possible explanations for the phenotype are
discussed.
In Arabidopsis and tomato, phytochrome A mediates a FR-light induced block of
greening when seedlings are transferred from FR to white light. This response is
considered with regard to the phytochrome A mutants of pea. Gibberellin (GA)-deficient lh-2 mutant plants of pea are dwarf in stature and show
increased seed abortion and decreased seed weight, compared with seeds of the
wild type. This aberrant seed development is associated with reduced levels of
active GA, and with an accumulation of abscisic acid (ABA) in young seeds.
Hormonal influence on seed development was investigated by construction of an lh-2 wil double mutant. The wi/ mutation blocks ABA biosynthesis, and reduces
ABA levels in young seeds by 10-fold, such that introduction of the wi/ mutation
reduces the endogenous ABA levels in young lh-2 seeds. However, this fails to
rescue the seeds from abortion. This indicates that the effects of lh-2 on seed
development are not mediated through increased ABA levels, and is consistent
with previous evidence that GAs are the controlling factor underlying the lh-2
seed phenotype in pea.

Item Type: Thesis (PhD)
Keywords: Gibberellins, Peas
Copyright Holders: The Author
Copyright Information:

Copyright 2000 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2000. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:49
Last Modified: 11 Mar 2016 05:54
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