Stresses: Freezing, heat, drought, salinity, flooding, xenobiotics
Cold stress:
        -cold intolerance in some plants
        -cold acclimatization needed in cold tolerant plants
Approaches:
        A) Manipulating known physiological traits:
                1) Osmoprotectant synthesis in Plants:
                        quaternary  amines(betaines), amino acids, sugar alcohols (e.g. mannitol)
        a) glycine betaine:  E. coli choline dehydrogenase into tobacco and potato
                        b) proline p5cs gene from moth bean into tobacco
                        c)  E. coli mannitol -1P dehydrogenase into Arabidopsis
                2) antifreeze proteins:
                        antifreeze proteins in flounder, seeds, carrots (26 species of                                         plants)
                        -neutralize ice nucleators and so inhibit ice recrystalization
                        e.g carrot protein in tobacco- cell extracts depressed .35-.6C
                        but no evidence for freezing protection in field. Cold-induced

        B)  Non-deductive approaches:
                1) Cold-induced genes:COR genes in Arabidopsis
                        over expression of selected COR genes 
                                -spinach CAP160 and CAP85 -cold induced genes
                                -constitutively expressed in tobacco- no change in chilling                                                    tolerance
                2) Genetics
                        Arabidopsis: esk mutants- mutants that display more freezing                                            tolerance than wt with no acclimatization       
                                -wt: non acclimate. -5.5C, w/ acclimatization -12.5C
                                -esk mutants: nonacclimat -6.8 - -10.6,  w/ acclimat -14.8C
                                -phenotypes of esk1 
                                        - 10x higher proline
                                        -see only subset of COR genes turned on 
                                        -growth inhibited at normal temperatures
        
                3) Engineering through regulation
                        Altering transcription factor can activate whole set of genes                                                   rather than just one or two genes at one time
                        -DRB1a transcriptional regulator that binds a drought-induced                                   and cold-induced element (DRE)
                        -DREB1a expression on two types of promoters:
                                1) CaMV 35S- cold stress tolerant but produced stunted                                          plants
                                2) stress-induced promoter from rd29A
                                -with stress, shows hyper induction of some COR genes
                                -see increased tolerance to freezing, drought and salinity

Links:
Description of the physiology of cold acclimatization in Arabidopsis Plant Physiology 120: 391-400
Arabidopsis esk mutants paper Proc. Natl. Acad. Sci (USA) vol 95 pp 7799.
Expression of choline oxidase (makes glycinebetaine) from Arthrobacter in Arabidopsis. Plant J. 22: 449-453

Warren Lab, UK - Database of dehydration/freezing/salt stress associated genes
                        -description of mutant studies and pictures

News article- engineering cold tolerance in grapes for Canada
List of references (with abstracts) for cold-tolerance

Last revised:April 30,  2001- Straney