Root extract of Boerhaavia diffusa L. induced systemic resistance in tobacco against Tobacco mosaic virus. A 30 kDa
protein was isolated as the active component, called BDP-30 on the basis of the molecular weight and source plant. BDP-30, a
glycoprotein, was found to be temperature and
protease resistant. It was basic, possessing a pI greater than 9.0. In-gel proteolytic digestion of BDP-30 generated two
peptides that possessed the amino acid sequence KLYDIPPLR and KVTLPYSGNYER by LC/MS/MS. Both
peptides shared absolute sequence identity with
trichosanthin, a
ribosome-inactivating protein from Trichosanthes kirilowii, and a 78 percent and 100 percent homology respectively with an RIP from Bryonia dioica,
bryodin. Further, effort was made to look at the fate of TMV in induced resistant Nicotiana tabacum cv. Xanthi, a systemic host of the virus, at specified days after inoculation in control and treated plants. TMV coat
protein (CP) was detected by immunoblot 7 days post inoculation up to 21 days in the control set, but not in treated resistant plants. TMV
RNA was detected by RT-PCR using TMV-CP specific primers. Resistant tobacco did not show presence of TMV
RNA up to 21 days of inoculation. This suggests that BDP-30 may be suppressing TMV replication.