|Tumlinson Iii, James|
Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2003
Publication Date: 4/24/2003
Citation: Huang, J., Cardoza, Y.J., Schmelz, E.A., Raina, R., Engelberth, J.E., Tumlinson III, J.H. 2003. Differential volatile emissions and salicylic acid levels from tobacco plants in response to different strains of pseudomonas syringae. Planta. 217:767-775. Interpretive Summary: Plants are often infected by bacteria, which in turn cause plants to respond in unique ways, one of which is production and release of volatile compounds. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS and University of Florida have been examining whether tobacco plants are able to release different types of volatile chemicals in response to attacks by different types of bacteria. They found that tobacco plants not only released many chemicals which were not released by healthy plants, but also, could differentiate between different bacterial attacks by releasing these chemicals in different amounts. This information may be very useful for providing early warning signs of plant infections and may be useful for identifying causative agents of plant disease infections
Technical Abstract: Pathogen-induced plant responses include changes in both volatile and non-volatile secondary metabolites. To investigate the role of bacterial pathogenesis in plant volatile emissions, tobacco plants, Nicotiana tabacum K326, were inoculated with virulent, avirulent, and mutant strains of Pseudomonas syringae. Volatile compounds released by inoculated tobacco plants were collected and analyzed. In the incompatible interactions involving P. syringae pv. maculicola ES4326 (Psm ES4326) or pv. tomato DC3000 (Pst DC3000), infected tobacco plants emitted quantitatively different, but qualitatively similar volatile blends of (E)-beta-ocimene, linalool, methyl salicylate (MeSA), indole, caryophyllene, beta-elemene, alpha-farnesene, and two unidentified sesquiterpenes. Plants treated with the hrcC mutant of Pst DC3000 (hrcC, deficient in the type III secretion system) released small quantities of many of the same compounds found in volatiles from Psm ES4326 or Pst DC3000-infected plants, with the exception of MeSA, which was undetectable or in trace amounts. A different blend, consisting of only MeSA and two unidentified sesquiterpenes was released by plants infected with the virulent P. syringae pv. tabaci (Pstb) in the compatible interaction. Overall, maximum volatile emissions occurred within 36 h post-inoculation in all the treatments except for the Pstb infection that produced peak volatile emissions about 60 h post-inoculation. (E)-beta-Ocimene was released in a diurnal pattern with the greatest emissions during the day and reduced emissions at night. Both avirulent strains, Psm ES4326 and Pst DC3000, induced accumulation of free salicylic acid (SA) within 6 h after inoculation and conjugated SA within 60 h and 36 h respectively. In contrast, SA inductions by the virulent strain Pstb occurred much later and conjugated SA increased slowly for a longer period of time, while the hrcC mutant strain did not trigger free and conjugated SA accumulations in amounts significantly different from control plants. Jasmonic acid, known to induce plant volatile emissions, was not produced in significantly higher levels in inoculated plants compared to the control plants in any treatments, indicating that induced volatile emissions from tobacco plants in response to P. syringae are not linked to changes in JA.