ABSTRACT: Transcriptional and metabolomic analysis of Ascophyllum nodosum mediated freezing tolerance in Arabidopsis thaliana

This is an abstract of a scholarly scientific article originally published in BMC Genomics on November 21, 2012. Read the full article by clicking on the image below.

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Background: We have previously shown that lipophilic components (LPC) of the brown seaweed Ascophyflum
nodosum (ANE) improved freezing tolerance in Arabidopsis tha/iana. However, the mechanism(s) of this induced
freezing stress tolerance is largely unknown. Here, we investigated LPC induced changes in the transcriptome and metabolome of A. tha/iana undergoing freezing stress.

Results: Gene expression studies revealed that the accumulation of proline was mediated by an increase in the
expression of the pro line synthesis genes PSCS I and P5CS2 and a marginal reduction in the expression of the
proline dehydrogenase (ProOH) gene. Moreover, LPC application significantly increased the concentration of total
soluble sugars in the cytosol in response to freezing stress. Arabidopsis sfr4 mutant plants, defective in the
accumulation of free sugars, treated with LPC. exhibited freezing sensitivity similar to that of untreated controls. The 1 H NMR metabolite profile of LPC-treated Arabidopsis plants exposed to freezing stress revealed a spectrum
dominated by chemical shifts (6) representing soluble sugars, sugar alcohols, organic acids and lipophilic
components like fatty acids, as compared to control plants. Additionally, 2D NMR spectra suggested an increase in the degree of unsaturation of fatty acids in LPC treated plants under freezing stress. These results were supported by global transcriptome analysis. Transcriptome analysis revealed that LPC treatment altered the expression of 1113 genes (5%) in comparison with untreated plants. A total of 463 genes (2%) were up regulated while 650 genes (3%) were down regulated.

Conclusion: Taken together, the results of the experiments presented in this paper provide evidence to support
LPC mediated freezing tolerance enhancement through a combination of the priming of plants for the increased accumulation of osmoprotectants and alteration of cellular fatty acid composition.

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