Isolation and characterisation of chloroplasts from Myrothamnus flabellifolius Welw.

Chloroplasts isolated from the resurrection plant Myrothamnus flabellifolius using trehalose gradients had a higher buoyant density than chloroplasts isolated from another resurrection plant Craterostigma wilmsii. The latter had the same buoyant density as those isolated from the desiccation-sensitive (DS) plant Pisum sativum. The increased buoyant density in M. flabellifolius was ascribed to the unusual ultrastructure of the thylakoid membranes. Standard chloroplast isolation protocols resulted in membrane damage in both resurrection plants. Trehalose rather than sucrose gradients were required for isolation of intact chloroplasts. Immunological studies showed that epitopes related to the desiccation stress protein dsp 21 from Craterostigma plantagineum were present in M. flabellifolius. Several small (10–15 kDa) unique stromal proteins were also present. Polyphenolics, including anthocyanins, accumulated in leaves and chloroplasts of M. flabellifolius during drying. Envisaged functions for these are maintenance of membrane integrity, chlorophyll masking and antioxidant protection. Metal (Ca2+, Cu2+, Fe2+, Mg2+ and Mn2+) concentrations declined and thylakoid membranes separated upon drying. We propose that this might be a mechanism to put a stasis on photosynthesis and minimise photo-oxidation damage under water stress conditions