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Title: The role of membrane proteins in Arabidopsis seedling development
Author: Jerram, Jonathan
ISNI:       0000 0001 3590 3486
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2007
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Plants have evolved sophisticated mechanisms to perceive changes in their environment and adapt their developmental program. Light is one of the most important factors and is most dramatically illustrated by seedling development. The transition from the dark-grown seedling to the photoautotrophic seedling is called de-etiolation and is accompanied by extensive changes in seedling morphology. Associated with this is a re-distribution of photoassimilates and other vital compounds and it is likely that changes in morphology require changes in the expression of a wide variety of transporter genes. To identify genes that are regulated by phytochrome A (phyA) during far-red light (FR) induced de-etiolation a transcriptomics approach was used. Transporter genes from a range of transport classes were identified using both the Arabidopsis Membrane Transporter (AMT) array (Maathius et at., 2003) and data from previously published array datasets including Wang et al. (2002). Examples of FR-light induced genes included the monosaccharide transporter STP 1, a Ca2 + ATPase, ACA2, the auxin transporter PIN4, a putative anthocyanin transporter ANM2 and two genes of unknown function, the Niemann-Pick C disease-like protein and FRIMP 1. Three FR-light repressed candidate transporter genes were also selected, RANI an ATP-dependent copper transporter, CAT4 an amino acid transporter and AHA2 an W-ATPase. Most of the genes were confirmed as being FR-light regulated by FR-light using RT -PCR and real-time PCR. The expression of some genes, including STPI was also shown to be mediated by other wavelengths of light including blue and red-light. To further study the role of these candidate genes in seedling de-etiolation insertional TDNA mutants were obtained and characterised. The stp 1, aca2, cat4 and aha2 mutants were obtained and interesting phenotypes were shown in some of these mutants. This included a reduced apical hook curvature and a reduction in hypocotyl elongation in the dark-grown cat4 mutant and a smaller aca2 seedling when grown in blue and white-light. A gene of unknown function was also established as being FR-light induced and termed FRIMP (Ear-red !jlduced Membrane ~rotein). Thejrimpi mutant had a number of phenotypic characteristics including the epinastic curling of the leaves, elongated petioles and an elongated hypocotyl in the FR-light grown seedling. A homolog to FRIMPl, termed FRIMP2 was revealed by protein sequence analyses and the phenotype ofjrimp2 was less severe thanjrimpi but also has an unusual leaf shape. The induction of FRIMP 1 in the FRlight grown phyA seedling indicated another photoreceptor other than phy A is important in perceiving FR-light. This is a unique expression profile. The FRIMP proteins may act directly as components of a light signalling pathway between phytochrome and other effector proteins. Alternatively they might transport a signalling molecule or may be receptors for such a molecule. The transcriptomics approach was successful in identifying FR-light responsive genes and indicated that membrane proteins are important in mediating light-regulated seedling development and changes in morphology.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available