Biochemical Aspects of Glandular Trichome-Mediated Insect Resistance in the Solanaceae

Glandular trichomes of wild Solanaceae produce an array of biochemical defenses against insects. This chapter reviews our knowledge of two of these mechanisms in the wild potato, Solanum berthaultii, and the wild tomato, Lycopersicon pennellii . Ruptured trichomes of S. berthaultii release a highly expressed, epidermis-specific polyphenol oxidase that polymerizes trichome exudate and entraps insects. Glandular trichomes of L. pennellii continuously secrete a viscous mixture of glucose esters which act as insect feeding deterrents. Glucose ester acyl constituents are composed of branched short and medium chain length fatty acids. Biosynthetic investigations reported here show that the branched amino acid biosynthetic pathway is used to form 4 and 5 carbon branched acyl groups which are subsequently elongated by acetate to form the medium chain acyl groups. It appears that, in both species, primary metabolic enzymes have been recruited and modified for trichome-specific insect resistance mechanisms.