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JXB Advance Access published online on February 4, 2008
Journal of Experimental Botany, doi:10.1093/jxb/erm333
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

Synchronicity of thermogenic activity, alternative pathway respiratory flux, AOX protein content, and carbohydrates in receptacle tissues of sacred lotus during floral development

Nicole M. Grant1, Rebecca E. Miller1,2, Jennifer R. Watling2 and Sharon A. Robinson1,*

1Institute for Conservation Biology, The University of Wollongong, Wollongong, NSW 2522, Australia
2School of Earth and Environmental Sciences, DP312, The University of Adelaide, Adelaide, SA 5005, Australia

* To whom correspondence should be addressed. E-mail: sharonr{at}uow.edu.au

The relationships between heat production, alternative oxidase (AOX) pathway flux, AOX protein, and carbohydrates during floral development in Nelumbo nucifera (Gaertn.) were investigated. Three distinct physiological phases were identified: pre-thermogenic, thermogenic, and post-thermogenic. The shift to thermogenic activity was associated with a rapid, 10-fold increase in AOX protein. Similarly, a rapid decrease in AOX protein occurred post-thermogenesis. This synchronicity between AOX protein and thermogenic activity contrasts with other thermogenic plants where AOX protein increases some days prior to heating. AOX protein in thermogenic receptacles was significantly higher than in post-thermogenic and leaf tissues. Stable oxygen isotope measurements confirmed that the increased respiratory flux supporting thermogenesis was largely via the AOX, with little or no contribution from the cytochrome oxidase pathway. During the thermogenic phase, no significant relationship was found between AOX protein content and either heating or AOX flux, suggesting that regulation is likely to be post-translational. Further, no evidence of substrate limitation was found; starch accumulated during the early stages of floral development, peaking in thermogenic receptacles, before declining by 89% in post-thermogenic receptacles. Whilst coarse regulation of AOX flux occurs via protein synthesis, the ability to thermoregulate probably involves precise regulation of AOX protein, most probably by effectors such as {alpha}-keto acids.

Key words: Alternative oxidase, alternative pathway respiration, Nelumbo nucifera, plant thermogenesis, starch

Received 11 November 2007; Accepted 28 November 2007


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