Differential esterase activity in leaves and roots of Centaurea ragusina L. as a consequence of salinity

Background and Purpose: Centaurea ragusina L. is an endemic Croatian plant species adapted to life in arid and salt-affected environments. Esterase activity (EST) and isoesterase patterns of C. ragusina plants cultured in vitro under saline and osmotic conditions were determined with an aim to evaluate the potential value of esterase activity as a biomarker of salt/osmotic stress as well as physiological significance of EST variations. Material and Methods: Rooted plantlets grown on MS ½ nutrient media supplemented with 150, 300, 450 or 600 mM NaCl or 300 mM mannitolwere investigated after 5, 10 and 15 days. Esterase activity was determined using either 1- or 2-naphthylacetate as substrates. Results and Conclusion: Esterase activities in shoots increased under low saline and mannitol treatments and decreased in response to increased saline treatments. The highest salt and concentration and mannitol stimulated EST activity in roots. In total, twelve and fourteen esterase isoenzymes were resolved in C. ragusina leaves and roots, respectively. Both salt and mannitol induced new esterase isoenzyme (EST11) while mannitol specifically induced two more (EST4-5); otherwise some bands were weakly expressed or even disappeared as a result of salinity in C. ragusina leaves. Two new isosterases (EST10-11) were resolved in mannitol- and salt-treated roots and four (EST2, EST12-14) only in salt-treated roots. Presented results demonstrate that esterase activities and their isoenzymic patterns could serve as useful bioindicators of salinity