Acid phosphatases (APases; E.C. 3.1.3.2) catalyze the hydrolysis of phosphate (Pi) from Pi monoesters and anhydrides within the acidic pH range. Induction of intracellular and secreted purple acid phosphatases (PAPs) is a widespread plant response to nutritional Pi-deficiency. The probable function of intracellular APases is to recycle Pi from expendable intracellular organophosphate pools, whereas secreted APases likely scavenge Pi from the organically bound Pi that is prevalent in most soils. Although the catalytic function and regulation of plant PAPs have been described, their physiological function in plants has not been fully established. Recent biochemical and proteomic studies indicated that AtPAP26 is the predominant intracellular (vacuolar) and a major secreted purple APase isozyme upregulated by Pi-starved (-Pi) Arabidopsis thaliana. The in planta function of AtPAP26 was assessed by molecular, biochemical, and phenotypic characterization of a homozygous Salk T-DNA insertion mutant. Loss of AtPAP26 expression resulted in the elimination of AtPAP26 transcripts and 55-kDa immunoreactive AtPAP26 polypeptides, correlated with a 9- and 5-fold decrease in extractable shoot and root APase activity, respectively, as well as a 40% reduction in secreted APase activity of –Pi seedlings. The results corroborate previous findings implying that AtPAP26 is: (i) the principal contributor to Pi starvation inducible APase activity in Arabidopsis, and (ii) controlled post-transcriptionally mainly at the level of protein accumulation. Total shoot free Pi level was about 40% lower in –Pi atpap26 mutants relative to wild-type controls, but unaffected under Pi-sufficient conditions. Moreover, shoot, root, inflorescence, and silique development of the atpap26 mutant was impaired during Pi deprivation, but unaffected under Pi-replete conditions, or during nitrogen or potassium-limited growth, or oxidative stress. The results suggest that the hydrolysis of Pi from organic-phosphate esters by AtPAP26 makes an important contribution to Pi-recycling and scavenging in –Pi Arabidopsis. / Thesis (Master, Biology) -- Queen's University, 2009-09-01 09:46:39.302
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/5325 |
| Date | 18 November 2009 |
| Creators | Hurley, Brenden A |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | 1127934 bytes, application/pdf |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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