Biotechnological approach in exploring vegetative desiccation tolerance: from aseptic culture to molecular breeding

What is remarkable about resurrection plants is the ability of vegetative tissues (root, shoot, stem, leaves) to tolerate dehydration of the tissues and then return as functional units on rehydration. This phenomenon made resurrection plants exciting targets for molecular analysis of the poikilohydric ability and drought tolerance. The protective mechanisms of vegetative desiccation tolerance appear to involve three major components, sugars, proteins and antioxidants. According to the recent scientific consensus all three are postulated to be involved in maintaining cellular integrity during the drying phases. The aim of this review is to establish a provisional hierarchy among these stress avoiding mechanisms that are associated with desiccation tolerance. The main reason for ranking these signal metabolites and protective agents is their potential importance in practical applications. Although vegetative desiccation tolerance is a complex trait both genetically and physiologically, there are already examples where outcomes of targeted studies in resurrection plants are going to be directly utilized to engineer crop plants genetically. Here we also show that conventional genetic transformation techniques, via in vitro plant regeneration systems, still represent an unavoidable part of the high-throughput technology chain of molecular breeding.