Trichomes are specialized epidermal structures that function as physical and chemical deterrents against arthropod herbivores. Aerial tissues of cultivated tomato (Solanum lycopersicum) are populated by several morphologically distinct trichome types, the most abundant of which is the type VI glandular trichome that produces various specialized metabolites. Here, the effect of the hairless (hl) mutation on trichome density and morphology, chemical composition, and resistance to a natural insect herbivore of tomato was investigated. The results show that the major effect of hl on pubescence results from structural distortion (bending and swelling) of all trichome types in aerial tissues. Leaf surface extracts and isolated type VI glands from hl plants contained wild-type levels of monoterpenes, glycoalkaloids, and acyl sugars, but were deficient in sesquiterpene and polyphenolic compounds implicated in anti-insect defence. No-choice bioassays showed that hl plants are compromised in resistance to the specialist herbivore Manduca sexta. These results establish a link between the morphology and chemical composition of glandular trichomes in cultivated tomato, and show that hl-mediated changes in these leaf surface traits correlate with decreased resistance to insect herbivory.
Bibliographical noteFunding Information:
We thank Erin Beach for assistance with plant growth and trichome density measurements, Guanghui Liu for performing genetic crosses, Tony Schilmiller for assistance with GC-MS analysis, and Ewa Danielewicz for expert assistance with SEM. We also thank members of the tomato trichome group for helpful discussions during the course of this work. We acknowledge the C.M. Rick Tomato Genetics Resource Center (University of California at Davis) for kindly providing tomato seed stocks. This research was supported by grants from the National Science Foundation (DBI-0604336) and the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy (grant DE-FG02-91ER20021).
- Acyl sugar
- Plant defence
- Plant-insect interaction
- Secondary metabolite