REVIEW ARTICLE Oligosaccharin—a new systemic factor in the acquisition of freeze tolerance in winter plants ALEKSEY I. ZABOTIN 1 , TATYANA S. BARISHEVA 1 , IRINA A. LARSKAYA 1 , TATYANA E. TOROSHINA 1 , OKSANA V. TROFIMOVA 1 , MICHAEL G. HAHN 2 & OLGA A. ZABOTINA 3 1 Institute of Biochemistry & Biophysics, Russian Academy of Sciences, Kazan, Russia, 2 University of Georgia, Complex Carbohydrate Research Center, Athens, GA, USA, and 3 Kazan State University, Department of Biochemistry, Kazan, Russia Abstract The acquisition of freeze tolerance in winter plants involves, among other cellular responses, activated catabolism of cell wall polysaccharides, thereby liberating oligosaccharides. One of these was identified as an oligosaccharin (physiologically active fragment) that most likely originates from hemicelluloses. Treatment of winter wheat seedlings with the oligosaccharin at 28C increased their freeze tolerance by *30%. Results obtained to date suggest that the oligosaccharin acts as an endogenous and systemic signaling molecule during cold adaptation. Abbreviations: LT 50 , temperature at which the efflux of 50% of the total electrolyte in the tissue occurs, which is equivalent to a 50% lethality of the seedlings; OS, oligosaccharin Key words: Cell wall, freeze-tolerance, cold hardening, oligosaccharin, Triticum aestivum L. Freeze tolerance of winter plants Plants are sessile organisms that rely on diverse mechanisms to assimilate the nutrients required for their growth, and to combat potential pathogens and accommodate to changes in their environment. An equally diverse number of signals, including the ‘classic’ plant hormones such as auxin, abscisic acid and ethylene, as well more recently identified signals such as salicylic acid, jasmonate and oligosaccharins play roles in the induction of the various responses of plants to their environment. Frost hardening is one adaptation to their environment that some temperate plant species, including such economically important crops as winter wheat and rye, are capable of undergoing. In nature, this adaptation process typically proceeds over the course of the fall and early winter and depends on the rate of decrease in the average daily temperature (Kacperska-Palacz, 1978). The gradual natural process of fall frost hardening can be reproduced in the laboratory over a much shorter time period (3 – 4 weeks) by using a two-phase acclimation procedure. This involves first exposing the plants to low non-freezing temperatures (*28C) for 5 – 7 days. After this phase, plants can survive mild frost conditions down to *7 68C. Further exposure of the ‘acclimated’ plants to sub- zero temperatures above the ice-nucleation tempera- ture of the tissue is required to achieve the level of frost tolerance exhibited by fully hardened plants (i.e., down to – 258C). Particularly the first phase of adaptation is essential for full expression of freeze tolerance and has been the focus of considerable research, since plant metabolism undergoes the most dramatic changes during this phase. Cell wall modifications during first stage of cold hardening The acquisition of freeze tolerance in winter plants is a complex process that involves diverse physiological and biochemical changes in all cellular compart- Correspondence: Olga A. Zabotina, Kazan State University, Department of Biochemistry, Kazan, Russia Current address: University of California-Riverside, Department of Botany, Batchelor Hall, Riverside, CA 92521, USA. Tel.: (951) 827-2486. E-mail: zabotina@ucr.edu Plant Biosystems, Vol. 139, No. 1, March 2005, pp. 36 – 41 ISSN 1126-3504 print/ISSN 1724-5575 online # 2005 Societa ` Botanica Italiana DOI: 10.1080/11263500500060601