Protein changes in the shoot-tips of vanilla (Vanilla planifolia) in response to osmoprotective treatments

Cryogenic storage of vanilla shoot-tips represents the safest biotechnological strategy for the long-term conservation of the vanilla germplasm, but successful cryopreservation depends on its tolerance to both dehydration stress imposed by cryoprotective treatments and thermal stress produced by immersion in liquid nitrogen. In this work, we evaluated the impact of various osmoprotective treatments on protein expression patterns in vanilla (Vanilla planifolia) shoot-tips subjected to successive dehydration steps prior to cryopreservation. Two-dimensional electrophoretic protein profiles of shoot-tips dissected from in vitro grown plants and preconditioned on semisolid media with 0.3 M sucrose for one day, and shoot-tips preconditioned, loaded with a solution of 0.4 M sucrose and 2 M glycerol, and subsequently exposed to plant vitrification solution 3 (50% (w/v) sucrose and 50% (w/v) glycerol), were compared with non-treated dissected shoot-tips. We observed an increase in the expression level of six protein spots (fold change exceeding 1.5) and a decrease (fold change not exceeding 0.6) of ten protein spots after preconditionig treatment, whereas the profiles after preconditioning, loading and exposure to vitrification solution showed an increase in the expression level of 21 protein spots and a decrease in the expression level of 13. Most proteins identified were down-regulated and belonged to groups of biosynthesis, folding, and protein degradation. Many others were related to energetic metabolism, defense, and cell structure. These preliminary results contribute to knowledge of the proteome of this species and partially clarify its sensitivity to osmotic dehydration treatments.