Author:
Chivasa Stephen,Berry James O.,ap Rees Tom,Carr John P.
Abstract
Thermogenesis in Arum species is induced by salicylic
acid (SA) and caused by activation of the alternative respiration pathway and
the alternative oxidase (AOX), resulting in heat production. The enzymes
phosphoenolpyruvate carboxylase (PEPCase) and
NAD-dependent malic enzyme (NAD-ME) also show dramatic increases in activity
during thermogenesis and are essential for heat generation. In this current
study, we characterized the timing and localization of changes in levels of
AOX, NAD-ME, and PEPCase polypeptide accumulation, and changes in
Ppc and Me mRNA accumulation, in
various Arum tissues during prethermogenic development
and during thermogenesis. In addition, changes in ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco) gene expression were analysed at the level
of rbcL protein and mRNA accumulation. AOX, PEPCase, and
NAD-ME all increased only in clubs during development, increasing
5–6-fold by the latest prethermogenic stage and remained at this level.
The induction of thermogenesis did not cause any changes in levels of AOX,
indicating that SA does not affect levels of the enzyme itself, but instead
must act to stimulate activity. Reported increases in NAD-ME activity during
club development correlated closely with mRNA and protein accumulation,
whereas PEPCase activity appears to be determined by post-transcriptional and
post-translational processes. Interestingly, Rubisco protein and mRNA were
found in relatively abundant amounts in clubs during early developmental
stages, and disappeared rapidly as the thermogenic enzymes began to increase
in abundance. The induction of thermogenesis by a synthetic inducer of plant
pathogen resistance, 2,6-dichloroisonicotinic acid, as well as the involvement
of SA and AOX in both processes, reinforces evidence for a link between
mechanisms controlling disease resistance in all plants and thermogenic
induction in Arum.
Subject
Plant Science,Agronomy and Crop Science
Cited by
15 articles.
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