Submitted to: Cryobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2006
Publication Date: 2/17/2007
Citation: Livingston, D.P., Herman, E.M., Premakumar, R., Tallury, S. 2007. Using arabidopsis thaliana as a model to subzero acclimation in small grains. Cryobiology. 54:154-163. Interpretive Summary: Arabidopsis is a common weed that is routinely used as a model plant to evaluate the genetic basis of various responses of crop plants to environmental stresses. In this research we wanted to see if Arabidopsis would respond to an acclimation to freezing stress that occurs in crop plants at below freezing temperatures (-3°C), called "subzero-acclimation". This is in contrast to freeze-stress acclimation that occurs at above freezing temperatures or "cold-acclimation". We found that Arabidopsis responds very well to subzero-acclimation. Its freezing tolerance went from a killing temperature of -13°C in fully cold-acclimated plants to -16°C in subzero-acclimated plants. We also found numerous proteins that were synthesized during subzero acclimation while plants were frozen for 3 days at -3°C. When we compared the internal anatomy of Arabidopsis with that of a common winter cereal crop (oats) using a light microscope we found several significant differences between the two. The central portion of the crown of Arabidopsis is made up of a number of very large cells and seems to have little function except to provide physical support to the growing tip. In winter cereals the central portion of the crown contains numerous water and sugar conducting vessels and is crucial to the plant. Freezing damage to this part of the plant was more extensive than the growing tip which was the same as has been found with winter cereals. Despite the clear anatomical differences between Arabidopsis and winter cereals Arabidopsis the fact that it does take advantage of acclimation at below freezing temperatures indicates that it would probably make a good model plant to study subzero-accimation.
Technical Abstract: The possibility of using Arabidopsis as a model plant to investigate cold-acclimation at subzero temperatures was evaluated by determining the extent to which Arabidopsis undergoes subzero-acclimation and by observing similarities to winter cereals in tissue damage following controlled freezing. Plants were grown and frozen under controlled conditions and percent survival was evaluated by observing regrowth after freezing. Two dimensional gels of plants that had been exposed to cold-acclimation were compared to those exposed to subzero-acclimation for 1 and 3 days. Paraffin embedded sections of plants were triple stained and observed under light microscopy. The LT50 of non-acclimated Arabidopsis decreased from about -6°C to about -13°C after 7 days of cold-acclimation at 3°C. Plants did not become more freezing tolerant beyond that achieved at 7d of cold-acclimation even up to 28d. However, after exposing cold-acclimated plants to -3'C for 3 days (subzero-acclimation) the LT50 was lowered an additional 3 degrees. Two dimensional gel analysis with differentially labeled proteins of proteome showed numerous protein changes from 1d to 3d of subzero-acclimation that were correlated with the acquisition of maximum acclimation. Histological observations of plants taken 1 week after freezing showed damage in the vascular tissue of roots and leaf axels but no damage to meristematic regions. The crown region of Arabidopsis was distinctly different than that of winter cereal crops and at least from a histological point of view, begs the question of whether this species is a valid model to understand freezing in crop plants. Despite clear histological differences in crown anatomy between Arabidopsis and winter cereals, defining the underlying mechanisms of subzero-acclimation in Arabidopsis may provide an experimental platform to extend improvements in winter hardiness to economically important crop species.