Transcriptional profile of the spring freeze response in the leaves of bread wheat (Triticum aestivum L.)

Measurement of the electrolyte leakage rates in wheat leaves indicated that there was no significant difference in susceptibility to -5 degrees C spring freeze stress among five bread wheat cultivars at the floret primordium-differentiating stage of spike development. A global transcriptional profile was created using the Affymetrix Wheat GeneChip microarray for one wheat cultivar (Yumai 34) under -5 degrees C freeze stress. After assaying genes with significant regulation at 1 and 3 days after -5 degrees C freeze stress, we identified 600 genes that were previously annotated as showing changes in expression of at least than two-fold at one or both of the time points. Among these genes, we further analysed 102 genes whose expression levels changed at least eight-fold after 1 or 3 days of freeze stress. These genes encoded an ice recrystallization protein, cold-related proteins, CBF transcription factors, calcium-dependent protein kinases, Na+/H+ antiporters, aquaporins, and many metabolic enzymes. The results of this study were compared with those of a previous study on the sub-freeze hardening response in wheat and spring freeze stress in wheat and barley. Many genes, including those encoding WCOR413, LEA, glycine-rich RNA-binding protein, ferritin, aquaporin 2, and a pathogen-induced protein, showed similar expression levels in these studies. Spring freeze stress is a complex phenomenon involving physiological mechanisms and multiple genes that had not been previously characterised.