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Vacuolar pyrophosphatases confer anoxia tolerance in rice by pumping protons across the tonoplast

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thesis
posted on 28.03.2022, 01:25 by Qinxiang Liu
Vacuolar pyrophosphatase (V-PPase) is induced by a number of abiotic stresses and is thus thought to play a role in plant adaptation. This thesis reports on the regulation of six V-PPase genes in rice (Oryza sativa L.) coleoptiles under anoxia, using cultivars with varying flood tolerance at the germination stage to test this hypothesis. Quantitative PCR time courses showed that one vacuolar pyrophosphatase (OVP3) was consistently induced by anoxia, particularly in the flood-tolerant cultivar Amaroo where it rose 20-fold in 2 h. Regulation of OVP3 expression under anoxia was investigated by analysis of putative OVP promoters. The putative OVP3 promoter contained more previously identified anoxia-inducible motifs than the promoters of the other five OVP genes. GUS activity in transgenic rice plants transformed with the OVP3 promoter region linked to the GUS reporter gene was induced by anoxia but not by salt or cold: GUS staining was visible mainly in the stele of seminal roots. Transgenic Arabidopsis plants overexpressing AVP1 (an Arabidopsis vacuolar pyrophosphatase) showed increased anoxia resistance as measured by survival and growth rate during the recovery period in air after anoxic treatment. Transgenic rice plants overexpressing OVP3 had higher anoxia tolerance which was supported by reduced solute leakage, more polarised membrane potentials and higher cytosolic pH under anoxia, compared to wild type roots. Membrane potentials of knockouts of the OVP gene family were depolarised under anoxia compared to wild type plants. I conclude that OVP3 is a key gene determining anoxia tolerance in rice seedlings via its effect on membrane properties. The importance of OVP3 is significant as a single gene determinant of anoxia tolerance.

History

Alternative Title

Vacuolar pyrophosphatases confer anoxia tolerance in rice

Table of Contents

1. Literature review -- 2. Bioinformatics: an in silico analysis of vacuolar pyrophosphatases -- 3. Transcript levels of the vacuolar pyrophosphatase genes under anoxia -- 4. Analysis of transcriptional regulation in T₁ seedlings transformed with the OVP3 promoter fused to GUS -- 5. Phenotype of rice transformed with a OVP3 overexpression construct -- 6. Downregulation of OVP genes by double stranded RNA interference -- 7. General discussion

Notes

Bibliography: pages 134-152 "March 2009 This dissertation is submitted for the degree of Doctor of Philosophy in the Macquarie University by Qinxiang Liu"

Awarding Institution

Macquarie University

Degree Type

Thesis PhD

Degree

PhD, Macquarie University, Division of Environmental and Life Sciences, Department of Biological Science

Department, Centre or School

Department of Biological Science

Year of Award

2009

Principal Supervisor

Brian Atwell

Additional Supervisor 1

Rachel A. Burton

Rights

Copyright Qinxiang Liu 2009. Copyright disclaimer: http://mq.edu.au/library/copyright Access to this thesis is restricted to Macquarie University staff and students. Staff and students of Macquarie University should contact researchonline@mq.edu.au to organise access.

Language

English

Extent

1 online resource (ix, 152 pages) illustrations (chiefly colour)

Former Identifiers

mq:71722 http://hdl.handle.net/1959.14/1277429