UVB radiation and 17‐hydroxygeranyllinalool diterpene glycosides provide durable resistance against mirid (Tupiocoris notatus) attack in field‐grown Nicotiana attenuata plants

Abstract

Depending on geographical location, plants are exposed to variable amounts of UVB radiation and herbivore attack. Because the role(s) of UVB in the priming and/or accumulation of plant defence metabolites against herbivores are not well understood, we used field-grown Nicotiana attenuata plants to explore the effects of UVB on herbivore performance. Consistent with previous reports, UVB-exposed plants accumulated higher levels of ultraviolet (UV)-absorbing compounds (rutin, chlorogenic acid, cryptochlorogenic acid and dicaffeoylspermidine). Furthermore, UVB increased the accumulation of jasmonic acid, jasmonoyl-L-isoleucine and abscisic acid, all phytohormones which regulate plant defence against biotic and abiotic stress. In herbivore bioassays, N. attenuata plants experimentally protected from UVB were more infested by mirids in three consecutive field seasons. Among defence metabolites measured, 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) showed strongly altered accumulation patterns. While constitutive HGL-DTGs levels were higher under UVB, N. attenuata plants exposed to mirid bugs (Tupiocoris notatus) had still more HGLDTGs under UVB, and mirids preferred to feed on HGLDTGs-silenced plants when other UVB protecting factors were eliminated by UVB filters. We conclude that UVB exposure not only stimulates UV protective screens but also affects plant defence mechanisms, such as HGL-DTGs accumulation, and modulates ecological interactions of N. attenuata with its herbivores in nature.

The HERBIVORE ELICITOR-REGULATED1 Gene Enhances Abscisic Acid Levels and Defenses against Herbivores in Nicotiana attenuata Plants

“…S5), the levels of CHA and DCS were rather similar or even lower in 48-h WOS-treated leaves compared with untreated controls. Differences in the accumulation patterns between CP and DCS (or CHA) were already noticed in several other independent studies (Kaur et al, 2010;Onkokesung et al, 2012;Dinh et al, 2013;Woldemariam et al, 2013). This suggests that simulated herbivory attack maintains, in a NaHER1-dependent manner, the higher levels of the "semiconstitutive" DCS (and possibly CHA) metabolites in the naturally aging leaves that can be considered as another part of the N. attenuata defense strategy.…”

“…cDNA synthesis, real-time quantitative PCR (qPCR), and calculation of relative transcript abundances of genes of interest were performed as described (Pfaffl et al, 2002;Dinh et al, 2013). The primer sequences used for qPCR (SYBR Green assays) are listed in Supplemental Figure S16.…”

Transcriptome profiling reveals differential gene expression of detoxification enzymes in a hemimetabolous tobacco pest after feeding on jasmonate-silenced Nicotiana attenuata plants

“…[36]. However, when single defense compounds were silenced, both DTGs [32, 37] and TPIs [38] emerged as clear determinants of T. notatus host choice.…”

Geranyllinalool Synthases in Solanaceae and Other Angiosperms Constitute an Ancient Branch of Diterpene Synthases Involved in the Synthesis of Defensive Compounds

“…Several studies have found negative correlation between total leaf HGL-DTG content and the mass of the larvae that feed on them (Jassbi et al, 2008;Dinh et al, 2013). Eleven HGL-DTGs that differ in sugar moieties and number of malonylesters have been isolated from Nicotiana attenuata.…”