Quantitative expression of cold-acclimation genes in wheat (Triticum aestivum L.)

Non-Peer ReviewedWinter wheat (Triticum aestivum L.) is seeded in the fall, regrowth resumes in spring, culminating in an early summer harvest. Yield is generally 20-25% higher than spring wheat. However, winter damage/kill can reduce yield. The low fall temperature allows the wheat plant to cold acclimate – a process during which physiological and biochemical changes occur resulting in the plant being able to withstand freezing temperatures. Specific cold regulated (COR) genes, such as Wcs120, are involved in these changes. Expression of COR genes are induced by transcriptional activators, such as WCBF1, in response to low temperature (LT). However, winter damage can still occur due to genetic differences limiting low temperature acclimation. An understanding of this cold acclimation/tolerance process will allow for better breeding strategies to improve winter wheat survival. Thus, the objective of this study was to determine the quantitative expression of some COR genes from field and growth chamber-grown winter and spring wheats using quantitative real-time PCR and establish their correlation, if any, to LT50 values (temperature at which 50% of plants are killed). Winter wheat (Norstar), spring wheat (Manitou) and two near-isogenic lines (Spring Norstar and Winter Manitou derived from reciprocal crosses of the two varieties) were used. Leaves were sampled on three dates (Sept. 29, Oct. 12 and Oct. 26, 2004) for the field grown plants and after 0, 2, 7, 14, 21, 28, 42, 56, 70, 84 and 98 days of LT acclimation for the growth chamber-grown plants. Relative expression of Wcs120 and WCBF1 genes were determined. Initial expression was high for both genes upon exposure to low temperature for all four lines from the growth chamber experiment. Expression decreased upon longer acclimation periods. The winter hardy wheat, Norstar, showed highest relative expression for both genes compared to the three other lines. This research implies that response to LT is very rapid and that accumulated LT tolerance (LT50) and LT tolerance gene translation, as revealed by accumulation of Wcs120, lags considerably