Pathogen-induced proteins with inhibitory activity toward Phytophthora infestans.
A bioassay using Phytophthora infestans was developed to determine whether inhibitory proteins are induced in pathogen-inoculated plants. Using this bioassay, AP24, a 24-kilodalton protein causing lysis of sporangia and growth inhibition of P. infestans, was purified from tobacco plants inoculated with tobacco mosaic virus. Analysis of the N-terminal amino acid sequence identified AP24 as the thaumatin-like protein osmotin II. The sequence was also similar to NP24, the salt-induced protein from tomato. Subsequently, we purified a protein from tomato plants inoculated with P. infestans that had inhibitory activities identical to those of the tobacco AP24. The N-terminal amino acid sequence of this protein was also similar to those of osmotin and NP24. In general, both the tobacco and tomato AP24 caused lysis of sporangia at concentrations greater than 40 nanomolar and severely inhibited hyphal growth at concentrations greater than 400 nanomolar. Because both proteins were induced by pathogen inoculation, we discussed the possible involvement of these proteins as a plant defense mechanism.
Woloshuk
C P
CP
MOGEN International NV, Leiden, The Netherlands.
Meulenhoff
J S
JS
Sela-Buurlage
M
M
van den Elzen
P J
PJ
Cornelissen
B J
BJ
D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D001681:Biological Assay; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000187:drug effects*; D010935:Plant Diseases; D010940:Plant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D010944:Plants / Q000382:microbiology*; D010947:Plants, Toxic; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000382:microbiology; D014027:Tobacco Mosaic Virus / Q000472:pathogenicity; D014774:Virulence
D000935:Antifungal Agents; D010940:Plant Proteins; C073139:osmotin protein, Nicotiana tabacum