Leaves of the Arabidopsis maltose exporter1 mutant exhibit a metabolic profile with features of cold acclimation in the warm.
BACKGROUND
Arabidopsis plants accumulate maltose from starch breakdown during cold acclimation. The Arabidopsis mutant, maltose excess1-1, accumulates large amounts of maltose in the plastid even in the warm, due to a deficient plastid envelope maltose transporter. We therefore investigated whether the elevated maltose level in mex1-1 in the warm could result in changes in metabolism and physiology typical of WT plants grown in the cold.


RESULTS
Grown at 21 °C, mex1-1 plants were much smaller, with fewer leaves, and elevated carbohydrates and amino acids compared to WT. However, after transfer to 4 °C the total soluble sugar pool and amino acid concentration was in equal abundance in both genotypes, although the most abundant sugar in mex1-1 was still maltose whereas sucrose was in greatest abundance in WT. The chlorophyll a/b ratio in WT was much lower in the cold than in the warm, but in mex1-1 it was low in both warm and cold. After prolonged growth at 4 °C, the shoot biomass, rosette diameter and number of leaves at bolting were similar in mex1-1 and WT.


CONCLUSIONS
The mex1-1 mutation in warm-grown plants confers aspects of cold acclimation, including elevated levels of sugars and amino acids and low chlorophyll a/b ratio. This may in turn compromise growth of mex1-1 in the warm relative to WT. We suggest that elevated maltose in the plastid could be responsible for key aspects of cold acclimation.
Australian Research Council Centre of Excellence in Plant Energy Biology, The University of Western Australia, Perth, Western Australia, Australia ; Institute of Biological, Environmental & Rural Sciences, Aberystwyth University, Aberystwyth, United Kingdom.
Sarah J
SJ
Purdy
John D
JD
Bussell
Christopher P
CP
Nunn
Steven M
SM
Smith
D000064:Acclimatization; D000596:Amino Acids / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D003080:Cold Temperature; D008320:Maltose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D010858:Pigmentation; D018515:Plant Leaves / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D018520:Plant Shoots / Q000254:growth & development
D000596:Amino Acids; D029681:Arabidopsis Proteins; C000590716:MEX1 protein, Arabidopsis; D026901:Membrane Transport Proteins; D002734:Chlorophyll; D008320:Maltose; D000077194:Chlorophyll A