Transcriptional Response of Cold-Acclimated Winter Wheat to Potentially Damaging Temperatures.

The ability of cold-acclimated wheat plants to survive freezing to several degrees below 0°C varies among wheat genotypes. While the transcriptional regulation of the cold acclimation process above 0°C has been studied extensively, very little is known of the changes in gene expression that may occur as the temperature decreases to potentially damaging levels well below 0°C. Using microarray and quantitative real - time PCR analysis, this study evaluated transcriptomic variation of cold-acclimated winter wheat plants as the temperature was lowered to -10°C, and then was either maintained at -10°C or was lowered further to -12°C. Expression levels of a total of 423 genes were significantly altered in these treatments; genes upregulated outnumbered those downregulated by about a 9: 1 ratio. Many of the most strongly responsive genes apparently were involved in transcription regulation or signal transduction. Most genes responded similarly in the very freezing tolerant cultivar Norstar and in the moderately freezing tolerant Tiber, but some genes responded in opposite fashion in the two cultivars. These results suggested that wheat crowns actively adapt as the temperature declines below 0°C to potentially damaging levels, and that genetic variation for this ability exists among cultivars.