Improved bioassay method for plant transformation inhibitors

A convenient and quantitative bioassay method for evaluating the efficiency of plant transformation by Agrobacterium tumefaciens is important to searc h plant transformation inhibitors, possible biochemical probes for study on its mechanism. Our previously reported method, in which the plant transfor mation had been detected by the expression of beta-glucuronidase in transfo rmed plants, was improved. The difference between the previous and the impr oved methods is the use of suspension-cultured cells of Ageratum conyzoides as the host plant instead of Nicotiana tabacum BY-2; this alteration of th e host enabled us to measure the beta-glucuronidase activity in plant cells not only fluorometrically but also colorimetrically. The enzyme activity e xpressed in the cells of A. conyzoides was nearly 100 times higher than tha t of N. tabacum BY-2, and was enough for detection by colorimetric measurem ent. The method, therefore, is useful for a convenient determination of inh ibitory activity against plant transformation.