Expression of heat shock proteins (HSPs) is a ubiquitous plant response under heat stress and is mainly regulated at the transcriptional level by heat shock factors (HSFs) that when activated recognize the heat shock elements (HSE) in the promoter region of' the HSPs, activating their transcription. ASCORBATE PEROXIDASE2 (APX2) was the first gene that was not a HSP but was heat dependent and HSF de'pendent. The mutant altered APX2 e.\pressiollll -1 (alxll -1) when exposed to heat stress showed higher HSPs, HSFs, APX2 expression and hydrogen peroxide (H20 2) levels than the wild type (WT). Expression of APX2 and H202 levels were still visible in alx11-1 under heat stress when placed in the dark or treated with 3-(3,4-dichlorophenyl)-I, I-dimethyl urea (DCMU), which is a specific inhibitor of photosystem II (PSII) . In addition no differences in photosynthetic electron flux were observed under heat stress. H20 2 production and signalling from other sources was considered for induction of heat related genes, for example from NADPH oxidases in the plasma membrane. In alxl 1-1, abscisic acid (ABA) signalling was considered to be linked to H20 2 production and signalling in the induction of heat related genes. Expression of the Hsa32 encoding a novel HSP like 32 kDa protein, Hsa32 which is considered necessary for acquired but not for basal thermotolerance, was highly expressed in the WT compared to the mutant. Screening of the F2 population from the cross between alxl1-l and the Landsberg erecta showed that the alx11-l mutation responsible for the altered expression in APX2 is a single recessive locus. Therefore it was suggested that aLd 1 mutation in Arabidopsis negatively regulates ABA mediated production of H20 2 under heat stress which in turn could affect the expression of HSPs necessary for basal thermotolerance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:495544 |
| Date | January 2008 |
| Creators | Vidigal, Patricia E. D. |
| Publisher | University of Essex |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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