Jasmonate (JA) is a lipid-derived hormone that regulates diverse aspects of plant immunity and development. An amino acid-conjugated form of JA, jasmonoyl–isoleucine (JA–Ile), stimulates binding of the F-box protein coronatine-insensitive 1 (COI1) to, and subsequent ubiquitin-dependent degradation of, jasmonate ZIM domain (JAZ) proteins that repress transcription of JA-responsive genes. The virulence factor coronatine (COR), which is produced by plant pathogenic strains of Pseudomonas syringae , suppresses host defense responses by activating JA signaling in a COI1-dependent manner. Although previous data indicate that COR acts as a molecular mimic of JA–Ile, the mechanism by which JA–Ile and COR are perceived by plant cells remains unknown. Here, we show that interaction of tomato COI1 with divergent members of the JAZ family is highly specific for JA–Ile and structurally related JA conjugates and that COR is ≈1,000-fold more active than JA–Ile in promoting this interaction in vitro . JA–Ile competes for binding of COR to COI1–JAZ complexes, demonstrating that COR and JA–Ile are recognized by the same receptor. Binding of COR to the COI1–JAZ complex requires COI1 and is severely impaired by a point mutation in the putative ligand-binding pocket of COI1. Finally, we show that the C-terminal region of JAZ3 containing the highly conserved Jas motif is necessary and sufficient for hormone-induced COI1–JAZ interaction. These findings demonstrate that COI1 is a critical component of the JA receptor and that COR exerts its virulence effects by functioning as a potent agonist of this receptor system.

We identified a cis -prenyltransferase gene, neryl diphosphate synthase 1 ( NDPS1 ), that is expressed in cultivated tomato ( Solanum lycopersicum ) cultivar M82 type VI glandular trichomes and encodes an enzyme that catalyzes the formation of neryl diphosphate from isopentenyl diphosphate and dimethylallyl diphosphate. mRNA for a terpene synthase gene, phellandrene synthase 1 ( PHS1 ), was also identified in these glands. It encodes an enzyme that uses neryl diphosphate to produce β-phellandrene as the major product as well as a variety of other monoterpenes. The profile of monoterpenes produced by PHS1 is identical with the monoterpenes found in type VI glands. PHS1 and NDPS1 map to chromosome 8, and the presence of a segment of chromosome 8 derived from Solanum pennellii LA0716 causes conversion from the M82 gland monoterpene pattern to that characteristic of LA0716 plants. The data indicate that, contrary to the textbook view of geranyl diphosphate as the “universal” substrate of monoterpene synthases, in tomato glands neryl diphosphate serves as a precursor for the synthesis of monoterpenes.

Summary: Plant trichomes come in a variety of shapes, sizes and cellular composition. Some types, commonly called glandular trichomes, produce large amounts of specialized (secondary) metabolites of diverse classes. Trichomes are implicated in a variety of adaptive processes, including defense against herbivores and micro‐organisms as well as in ion homeostasis. Because trichomes protrude from the epidermis and can often be easily separated from it and harvested, the mRNAs, proteins and small molecules that they contain are unusually accessible to analysis. This property makes them excellent experimental systems for identification of the enzymes and pathways responsible for the synthesis of the specialized metabolites found in these structures and sometimes elsewhere in the plant. We review the literature on the biochemistry of trichomes and consider the attributes that might make them highly useful targets for plant metabolic engineering.

Compounds of the terpenoid class play numerous roles in the interactions of plants with their environment, such as attracting pollinators and defending the plant against pests. We show here that the genome of cultivated tomato (Solanum lycopersicum) contains 44 terpene synthase (TPS) genes, including 29 that are functional or potentially functional. Of these 29 TPS genes, 26 were expressed in at least some organs or tissues of the plant. The enzymatic functions of eight of the TPS proteins were previously reported, and here we report the specific in vitro catalytic activity of 10 additional tomato terpene synthases. Many of the tomato TPS genes are found in clusters, notably on chromosomes 1, 2, 6, 8, and 10. All TPS family clades previously identified in angiosperms are also present in tomato. The largest clade of functional TPS genes found in tomato, with 12 members, is the TPS-a clade, and it appears to encode only sesquiterpene synthases, one of which is localized to the mitochondria, while the rest are likely cytosolic. A few additional sesquiterpene synthases are encoded by TPS-b clade genes. Some of the tomato sesquiterpene synthases use z,z-farnesyl diphosphate in vitro as well, or more efficiently than, the e,e-farnesyl diphosphate substrate. Genes encoding monoterpene synthases are also prevalent, and they fall into three clades: TPS-b, TPS-g, and TPS-e/f. With the exception of two enzymes involved in the synthesis of ent-kaurene, the precursor of gibberellins, no other tomato TPS genes could be demonstrated to encode diterpene synthases so far.