Enhancing rice callus regeneration by extracellular products of Tolypothrix tenuis (Cyanobacteria)

Abstract

Cyanobacteria produce a wide array of substances with activity in many biological systems. The aim of the present research was to compare the effect of differently treated extracellular products (EP) from Tolypothrix tenuis (Cyanobacteria) on rice plantlet regeneration as well as on the pigments, protein, total free porphyrin contents, and 5-aminolevulinate dehydratase (ALA-D) activity in rice callus during differentiation. Rice embryo calli were regenerated in Murashige & Skoog medium supplemented with EP with protein (EPp) or without protein (EPnp) or autoclaved (EPa), as well as with benzyladenine (BA) and benzyladenine + naphthaleneacetic acid (BA + NAA). At day 75, calli percentage regeneration were: EPnp (84%), EPp (58%), BA + NAA (45%), BA (44%), EPa (40%). The same trend was found for chlorophyll a, b, total and carotenoid contents. Protein content in BA, BA + NAA and EPnp treatments was 35% higher than in EPp and EPa. Total free porphyrin was similar in all treatments. ALA-D activity in BA, EPp and EPa treatments was 28% higher than in BA + NAA and EPnp. The extracellular bioactive substance(s) from T. tenuis would contain a mixture of thermolabile plant growth regulators that replaced and improved the effects of synthetic plant growth regulators on rice callus organogenesis. Calli were rhizogenic in all the regeneration media tested. The pigment content of the calli was related to percentage regeneration but not to the total free porphyrin and ALA-D activity.