Abstract
Paleoendemic species of the monophyletic genus Ramonda (R. myconi, R. serbica and R.~nathaliae) are the remnants of the Tertiary tropical and subtropical flora in Europe. They are the rare resurrection plants of Northern Hemisphere temperate zone. Ramonda serbica and R. nathaliae are chorologically differentiated in the Balkan Peninsula and occupy similar habitats in calcareous, northward slopes in canyons and mountainsides. They remain well-hydrated during spring, late autumn and even in winter. In summer and early autumn when plants are subjected to drought and thermal stress, their desiccation tolerance comes into operation and they fall into anabiosis. Investigations revealed the permanent presence of ubiquitine and its conjugates, high amounts of oxalic acid and proline. Both species are homoiochlorophyllous. It enables them to rapidly resume photosynthesis upon rehydration, but also makes them susceptible to reactive oxygen species formation. Dehydration induces activation of antioxidative enzymes (ascorbate peroxidase, glutathione reductase, polyphenol oxidase), increase in amounts of AsA and GSH, phenolic acids, dehydrins, sucrose, and inorganic ions. Plasma membranes, characterized by high amount of cholesterol, are subjected to decrease in membrane fluidity mostly on account of increased level of lipid saturation. Cytogenetic analysis revealed that R. nathaliae is a diploid (2n = 48) and probably evolutionary older species, while R. serbica is a hexaploid (2n = 144). Two species live together in only two localities forming hybrid individuals (2n = 96). Polyploidization is the major evolutionary mechanism in the genus Ramonda that together with hybridization ability indicates that these relict species which have preserved an ancient survival strategy are not the evolutionary “dead end.”The species of the genus Ramonda are promising sources of data important for understanding the complex strategy of resurrection plants’ survival, appraised through a prism of their evolutionary and adaptive potential for multiple environmental stresses.
Highlights
The Balkan Peninsula is one of the most important parts within the Mediterranean “hot spot” area and is globally distinguished as a reservoir of biological diversity (Myers et al, 2000)
The desiccation-related effects on level of ubiquitin and its conjugates are poorly understood, our results demonstrate that level of protein ubiquitination is increased during dehydration phase D2 (RWC 55%) and might be the result of higher proteolysis rate by the 26S proteasome caused by more pronounced water depletion (Jovanovicet al., 2010)
We found that considerable amounts of dehydrins were present already in fully hydrated leaves and that some of them were upregulated during dehydration/rehydration cycle (Jovanovicet al., 2011)
Summary
The Balkan Peninsula is one of the most important parts within the Mediterranean “hot spot” area and is globally distinguished as a reservoir of biological diversity (Myers et al, 2000). It harbors several desiccation tolerant and preglacial endemo-relict species of the tropical-subtropical family Gesneriaceae These are the exceptional examples of floristic evolutionary diversification and biogeographical differentiation within South-European eumediterranean and paramediterranean area. Gesneriaceae has predominantly pantropical and pansubtropical distribution with only a small number of species extending to temperate regions Among these are three genera from South Europe. With the exception of Ramonda myconi which inhabits the Iberian Peninsula, all others (R. serbica and R. nathaliae, Haberlea rhodopensis, and Jankaea heldreichii) are spread in the Balkan Peninsula. These Tertiary relict and endemic species are perennial, long-lived, and slow-growing poikilohydric plants.
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