Abstract
The relationship between Mg-protoporphyrin IX (Mg-Proto IX) signals and plant’s tolerance to cold stress is investigated. Arabidopsis seedlings grown for 3 weeks were pretreated with 2 mM glutamate (Glu) and 2 mM MgCl2 for 48 h at room temperature to induce Mg-Proto IX accumulation. Then cold stress was performed at 4°C for additional 72 h. Glu + MgCl2 pre-treatments alleviated the subsequent cold stress significantly by rising the leaf temperature through inducing Mg-Proto IX signals. The protective role of Glu + MgCl2 treatment was greatly compromised in the mutants of Mg-Proto IX synthesis, Mg-Proto IX signaling, and cyanide-resistant respiration. And the enhancement of cold-responsive gene expression was greatly compromised in the mutants of Mg-Proto IX synthesis, Mg-Proto IX signaling and ABA signaling, but not in the mutant of cyanide-resistant respiration. Cold stress promoted cyanide-resistant respiration and leaf total respiration exponentially, which could be further induced by the Glu + MgCl2 treatment. Mg-Proto IX signals also activate antioxidant enzymes and increase non-enzymatic antioxidants [glutathione but not ascorbic acid (AsA)] to maintain redox equilibrium during the cold stress.
Highlights
Magnesium (Mg) is one of the essential macronutrients for plants
Mg-Proto-IX-signal-induced CNresistant respiration plays a key role in heat production during the cold stress
The reduced glutathione is involved in Mg-Proto-IX-signal-mediated cold tolerance
Summary
Magnesium (Mg) is one of the essential macronutrients for plants. Mg is an irreplaceable constituent of the chlorophyll (Chl) and regulates over 300 enzyme activities (especially for ATPases, protein kinases, glutathione synthase, phosphatases, and RNA polymerases), which are involved in ion absorption and transport (da Silva et al, 2014). Mg2+ is the cofactor of a large number of important enzymes and plays a key role in the stabilization of DNA and RNA. The most prominent example of enzyme reactions where Mg2+ is irreplaceable, are the processes associated with the phosphorylation-dephosphorylation cycle and energy transfer between ATP and ADP (Maathuis, 2009)
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