RNASE IN LASALLIA-HISPANICA AND CORNICULARIA-NORMOERICA - MULTIPLICITY OF ELECTROMORPHS AND ACTIVITY CHANGES DURING A HYDRATION-DEHYDRATIONCYCLE

The presence of RNase activity has been detected in the two saxicolous lichen species, Lasallia hispanica (Frey) Sancho & Crespo and Cornicu laria normoerica (Gunn.) DR. Activity was localized in the soluble fra ction and had an acid optimum pH in both species. When proteins from t he soluble fraction of the two lichens were separated by isoelectric f ocusing, multiple electromorpha with RNase activity were detected, L. hispanica RNase was separated into seven bands, characterized by pls 7 , 6.28, 4.58, 4.45, 4.25, 3.95, and 3.47. In C. normoerica four bands were detected, with pls of 6.28, 3.98, 3.57, and 3.39. The molecular m ass of the main RNase of L. hispanica estimated by SDS-PAGE was 31.86 kDa, which corresponds to the 33 kDa estimated for the undenatured RNa se by gel chromatography. Proteins from C. normoerica were resolved by SDS-PAGE in three bands, with estimated molecular mass of 36.07 kDa, 31.86 kDa and 17.13 kDa. In order to improve the detection of RNase ac tivity, gels were incubated after the run (electrophoresis or isoelect ric focusing) in a RNA solution, instead of including the substrate in the gel, In both species, RNase activity increased during hydration a nd decreased during desiccation. This pattern of activity resembles th at of other enzyme activities in lichens, which decrease in response t o water deficits, and is different from the response of other poikiloh ydrous organisms such as bryophytes. These results are discussed in re lation to the mechanisms that lichens have to withstand dehydration.