|Stipanovic, Robert - Bob|
Submitted to: Phytoparasitica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/9/2007
Publication Date: 8/5/2007
Citation: Golubinko, Z., Akhunov, A., Beresneva, Y., Khashimova, N., Mustakimoval, E., Ibragimov, F., Abdurashidova, N., Stipanovic, R.D. 2007. Induction of peroxidase as a disease resistance response in resistant (Hibiscus trionum) and susceptible (Althea armeniaca) species in the family Malvaceae. Phytoparasitica. 35:401-413. Interpretive Summary: Cotton producers in the U.S. and Uzbekistan suffer substantial losses due to the wilt pathogen, Verticillium dahlia. Cotton is a member of the Malvaceae Family. Hibiscus trionum, a member of the Family Malvaceae that grows wild in Uzbekistan, was highly resistant to this pathogen, while Althea armeniaca, which is also a member of the Malvaceae, was highly susceptible to this pathogen. Information on why these plants differ in resistance to the pathogen could provide guidance for increasing cotton’s resistance to this pathogen. It was found that both the resistant and the susceptible plants produce chemicals (peroxidases) that protect the plant from attack by microorganisms. However, the resistant plant produces them quicker and in larger amounts than the susceptible plant. Thus, the resistant plant is already producing these compounds in just one hour, while the susceptible plant has not begun to ramp up production at the end of 18 hours. Furthermore, when the resistant plant is attacked by the pathogen one of the chemicals it produces actually attaches itself to the cell wall of the pathogen, while the susceptible plant fails to produce this type of chemical when it is attacked. The ability of the chemical to directly attach itself to the pathogen could be one reason why the resistant plant is more successful in warding off attack. This same phenomena may be important in cotton’s resistance to Verticillium dahliae.
Technical Abstract: Pathogen induced biosynthesis of peroxidase in two wild species of Malvaceae, Hibiscus trionum and Althea armeniaca was studied. After inoculation with the fungal pathogen Verticillium dahliae, peroxidase activity increased more rapidly in the resistant plant (H. trionum) than in the susceptible plant (A. armeniaca). Increased peroxidase activity was noted within one to five hours after inoculation of H. trionum, and decreased after 18 hours. After 5 days, the levels were not different from that of the mock inoculated control. In A. armeniaca, peroxidase activity was only marginally different from the mock inoculated control, even after 18 hours, but it was significantly higher after 5 days. Electrophoretic analysis of inoculated tissue extracts showed the occurrence of two new peroxidase isoforms in H. trionum. A chitin affinity chromatography column showed that one of these was a chitin binding peroxidase isozyme; its concentration increased significantly after inoculation. The ability of the peroxidase to bind with chitin in the cell wall of the pathogen may facilitate its destruction. New isoforms also occurred in A. armeniaca, but they did not bind to chitin. The concentration of the two chitin binding peroxidase isozymes in A. armeniaca did not increase after inoculation.