Evidence of cyclical light/dark-regulated expression of freezing tolerance in young winter wheat plants

Abstract

The ability of winter wheat (Triticum aestivum L.) plants to develop freezing tolerance through cold acclimation is a complex rait that responds to many environmental cues including day length and temperature. A large part of the freezing tolerance is conditioned by the C-repeat binding factor (CBF) gene regulon. We investigated whether the level of freezing tolerance of 12 winter wheat lines varied throughout the day and night in plants grown under a constant low temperature and a 12-hour photoperiod. Freezing tolerance was significantly greater (P<0.0001) when exposure to subfreezing temperatures began at the midpoint of the light period, or the midpoint of the dark period, compared to the end of either period, with an average of 21.3% improvement in survival. Thus, freezing survival was related to the photoperiod, but cycled from low, to high, to low within each 12-hour light period and within each 12-hour dark period, indicating ultradian cyclic variation of freezing tolerance. Quantitative real-time PCR analysis of expression levels of CBF genes 14 and 15 indicated that expression of these two genes also varied cyclically, but essentially 180° out of phase with each other. Proton nuclear magnetic resonance analysis (1H-NMR) showed that the chemical composition of the wheat plants' cellular fluid varied diurnally, with consistent separation of the light and dark phases of growth. A compound identified as glutamine was consistently found in greater concentration in a strongly freezing-tolerant wheat line, compared to moderately and poorly freezing-tolerant lines. The glutamine also varied in ultradian fashion in the freezing-tolerant wheat line, consistent with the ultradian variation in freezing tolerance, but did not vary in the less-tolerant lines. These results suggest at least two distinct signaling pathways, one conditioning freezing tolerance in the light, and one conditioning freezing tolerance in the dark; both are at least partially under the control of the CBF regulon.

Zoysiagrass (Zoysia spp.) accessions differ in nitrogen cycling during a simulated seasonal senescence

“…This demonstrates the complexity of regulation of senescence and acclimation as affected by the sensitivity to environmental signals and the relative importance of temperature and photoperiod (Malyshev et al, 2014;Van Esbroeck et al, 2004). Evidence of combined regulation of freezing tolerance was reported in winter wheat by Skinner et al (2018). Further research in turfgrass is needed on these topics.…”

Genome‐wide association analysis of freezing tolerance in soft red winter wheat

“…We additionally included another winter wheat cultivar Norstar as a highly freezing-tolerant control (Grant, 1980). This line was developed in Saskatoon, Canada, and has been used in several studies investigating the genetic basis of freezing tolerance Mahfoozi et al, 2006;Skinner et al, 2018).…”