Abstract
BackgroundLight and temperature are the key abiotic modulators of plant gene expression. In the present work the effect of light under low temperature treatment was analyzed by using microarrays. Specific attention was paid to the up and down regulated genes by using promoter analysis. This approach revealed putative regulatory networks of transcription factors behind the induction or repression of the genes.ResultsInduction of a few oxidative stress related genes occurred only under the Cold/Light treatment including genes encoding iron superoxide dismutase (FeSOD) and glutathione-dependent hydrogen peroxide peroxidases (GPX). The ascorbate dependent water-water cycle genes showed no response to Cold/Light or Cold/Dark treatments. Cold/Light specifically induced genes encoding protective molecules like phenylpropanoids and photosynthesis-related carotenoids also involved in the biosynthesis of hormone abscisic acid (ABA) crucial for cold acclimation. The enhanced/repressed transcript levels were not always reflected on the respective protein levels as demonstrated by dehydrin proteins.ConclusionCold/Light up regulated twice as many genes as the Cold/Dark treatment and only the combination of light and low temperature enhanced the expression of several genes earlier described as cold-responsive genes. Cold/Light-induced genes included both cold-responsive transcription factors and several novel ones containing zinc-finger, MYB, NAC and AP2 domains. These are likely to function in concert in enhancing gene expression. Similar response elements were found in the promoter regions of both the transcription factors and their target genes implying a possible parallel regulation or amplification of the environmental signals according to the metabolic/redox state in the cells.
Highlights
MethodsPlant material and growth conditions Arabidopsis thaliana ecotype Col-0 seeds were germinated in 50% vermiculite/50% soil and grown in controlledenvironment chambers at 23°C and under 100 μmol photons m-2 s-1 (8-hour-photoperiod) for 8 weeks
Light and temperature are the key abiotic modulators of plant gene expression
Physiological consequences of the cold treatments on Arabidopsis photosynthetic apparatus Eight-week old Arabidopsis plants were transferred from normal growth temperature (23°C, 60% relative humidity) directly to low temperature (3°C, 60% relative humidity) under normal growth light (100 μmol photons m-2 s-1) or to darkness for eight hours
Summary
Plant material and growth conditions Arabidopsis thaliana ecotype Col-0 seeds were germinated in 50% vermiculite/50% soil and grown in controlledenvironment chambers at 23°C and under 100 μmol photons m-2 s-1 (8-hour-photoperiod) for 8 weeks. Cold treatments for 8 hours were performed at 3°C (measured from the bottom of the leaf using digital thermocouple). To allow full CO2 assimilation before the treatments, plants were transferred after 2 hours of the beginning of light period directly from growth temperature to the low temperature treatment. The cold treatments were performed either in the light (100 μmol photons m-2 s-1) or in the dark. The dark treatment at 23°C for 8 hours was performed after 2 hours of the beginning of light period. 2 to 3 g of leaf material from 4–6 individual plants was collected and directly frozen in liquid nitrogen
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