Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/24/2004
Publication Date: 9/24/2004
Citation: Herman, E.M., Rotter, K., Chen, S., Livingston, D.P. 2004. Enhancement of freezing tolerance by frost temperature involves complex biological mechanisms [abstract].
Technical Abstract: Previously-cold-acclimated plants can acquire an additional 3-5 C of freezing tolerance in LT50 tests when exposed to a frost temperature of -3 C for 12-18 h. This treatment replicates the overnight frost that occurs in the weeks leading to over-wintering by freezing-tolerant plants. This additional acquired freezing tolerance is termed second phase (2PH) to differentiate it from cold acclimation acquired at cold non-freezing temperatures. Using wheat as a model, we have obtained results indicating that 2PH resulting from -3 C exposure is accompanied by complex biological changes. Cold acclimation does not appear to induce shifting of intracellular water to extracellular space. In contrast, 2PH does induce the movement of intracellular water to extracellular space, differentiating the 2PH response from cold acclimation. Using a variety of assays, including DNA arrays, RT-PCR, 2D gels with mass spectroscopy identification of proteins, and electron microscopy, changes have been observed to occur as a consequence of 2PH and the acquisition of added freezing tolerance. Many unknown and stress-related genes are up-regulated by 2PH, while many genes related to photosynthesis and plastids are among those that are down-regulated. Protein changes resulting from 2PH are more subtle than those resulting from cold acclimation and many of the protein changes appear to be a loss of specific proteins rather than the appearance of new proteins. Second-phase freezing tolerance results in alterations of organelle structure, including the Golgi. The results obtained indicate that the overt 2PH effect of enhanced freezing tolerance after 12-18 h at -3 C exposure is correlated with a wide diversity of changes, indicating that the additional 2PH-acquired freezing tolerance is likely the result of complex processes.