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The role of polyamine catabolism in Arabidopsis thaliana development and senescence

Alharbi, Basmh 2017. The role of polyamine catabolism in Arabidopsis thaliana development and senescence. PhD Thesis, Cardiff University.
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Plant polyamines (PAs) are involved in several physiological processes and their application delays senescence. PA catabolism via amine oxidase (AO) activity is essential in regulating PA levels and generating compounds essential in the physiological interactions during development and stresses. AOs include polyamine oxidases (PAOs) and copper amine oxidases (CuAOs). In Arabidopsis, CuAOs are encoded by a gene family of ten members. The expression pattern of each AtCuAO gene was investigated in individual Arabidopsis leaves at four developmental stages using real-time PCR (qRT-PCR). Seven members of the family showed distinct patterns of expression during leaf development and senescence. These can be divided into two groups: the first is highly expressed at early stages whereas transcripts of the other group, which includes AtCuAO4, reached maximum levels at senescence. Growth and senescence of three AtCuAO4 over-expression lines and two AtCuAO4 mutants were compared to wild-type (WT) under optimal conditions. Results demonstrated a clear phenotypic response to AtCuAO4 mutation represented by late flowering and delayed senescence, although dark-induced senescence was unaffected. Since previous studies on gibberellic acid (GA)-deficient mutants showed a delay in flowering, mutant lines were treated with gibberellin, which rescued the mutant phenotype. Furthermore, the levels of some GA biosynthetic and flowering transcripts (by qRT-PCR) were lower in the mutants than in WT. Content of PAs both pre-bolting and post-bolting was altered in AtCuAO4 mutation. To avoid functional redundancy between AtCuAOs, two different artificial microRNA (amiRNA) clones were transformed into Arabidopsis. The amiRNAs were predicted to silence several AtCuAOs simultaneously. Artificial microRNA plants showed a wide range of phenotypic variations indicating the potential value of this approach for investigating the function of AtCuAOs. Overall this work suggests the possibility of partial functional redundancy between AtCuAOs an, indirect role of these genes in senescence retardation and a link between PAs and GA signalling.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > QK Botany
Date of First Compliant Deposit: 10 April 2017
Last Modified: 20 Apr 2021 09:46

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