FIG 4.

Induction of R. etli virE promoter activity by extracts from host and nonhost plant species. The level of expression of the lacZ reporter under the control of the R. etli virE promoter (R. etli virEprom-lacZ) was determined by measuring the β-galactosidase activity in the cell culture of wild-type R. etli carrying p42a supplemented with identical volumes of ethanol (mock-induced control), AS, and ethanolic extracts of the roots and shoots of plantlets from the indicated species. All data represent average values from three independent experiments with the indicated standard deviations. Asterisks indicate the statistical significance (*, P < 0.05; **, P < 0.01) of the difference between the experimental data for noninduced control and AS-induced cells, as determined by the two-tailed Student's t test.