Electrophoretic protein patterns and peroxidase activity related to morphogenesis in Mammillaria gracillis tissue culture

The cactus Mammillaria gracillis Pfeiff. was propagated in vitro on Murashige and Skoog (MS) medium without any growth regulators. At the bases of some plants abundant callus masses developed. Lower agar and higher MS salt concentrations stimulated callus pro­ duction. In the culture, morphologically normal and hyperhydric shoots were regenerated. The growth of crown-gall tumour was induced on disc-like explants of in vitro grown plants infected with Agrobacterium tumefaciens, B6S3 strain. Calli appeared on both in­ fected and control explants. The tumorous tissue grew more intensively than the control. The transformed character of the callus was confirmed by PCR amplification of a gene 6a of T-DNA. Gene expression in cactus shoots (grown in vitro or in pot), callus, hiperhydric and morphologically normal regenerated shoots and crown-gall tumour were analysed at the level of the electrophoretic pattern of soluble proteins. Some tumour-specific poly­ peptides were detected (76, 32-39, and 23 kDa). That of 42 kDa was highly expressed in callus and hyperhydric shoots. A faint 58 kDa band was found in all extracts except in the pot-grown shoot. Relatively high peroxidase activity was detected in callus and shoot regenerants and it was lower in tumour and the lowest in plant shoots.