An unbiased approach elucidates variation in ( S )-(+)-linalool, a context-specific mediator of a tri-trophic interaction in wild tobacco

Abstract

Plant volatile organic compounds (VOCs) mediate many interactions, and the function of common VOCs is especially likely to depend on ecological context. We used a genetic mapping population of wild tobacco, Nicotiana attenuata, originating from a cross of 2 natural accessions from Arizona and Utah, separated by the Grand Canyon, to dissect genetic variation controlling VOCs. Herbivory-induced leaf terpenoid emissions varied substantially, while green leaf volatile emissions were similar. In a field experiment, only emissions of linalool, a common VOC, correlated significantly with predation of the herbivore Manduca sexta by native predators. Using quantitative trait locus mapping and genome mining, we identified an (S)-(+)-linalool synthase (NaLIS). Genome resequencing, gene cloning, and activity assays revealed that the presence/absence of a 766-bp sequence in NaLIS underlies the variation of linalool emissions in 26 natural accessions. We manipulated linalool emissions and composition by ectopically expressing linalool synthases for both enantiomers, (S)-(+)- and (R)-(−)-linalool, reported to oppositely affect M. sexta oviposition, in the Arizona and Utah accessions. We used these lines to test ovipositing moths in increasingly complex environments. The enantiomers had opposite effects on oviposition preference, but the magnitude of the effect depended strongly both on plant genetic background, and complexity of the bioassay environment. Our study reveals that the emission of linalool, a common VOC, differs by orders-of-magnitude among geographically interspersed conspecific plants due to allelic variation in a linalool synthase, and that the response of a specialist herbivore to linalool depends on enantiomer, plant genotype, and environmental complexity.

Allelic differences of clustered terpene synthases contribute to correlated intra-specific variation of floral and herbivory-induced volatiles in a wild tobacco

“…To examine this, we further measured the floral volatiles of the 25 genotypes and compared the emissions of ( E )-β-ocimene, linalool and ( E )-α-bergamotene emission in the HIPVs and floral volatiles. We found that linalool, which was found in both floral volatiles and HIPVs, showed no correlation among the different genotypes, consistent with a recent study (He et al ., 2019). However, the variations of ( E )-α-bergamotene and ( E )-β-ocimene emission in HIPVs and floral volatiles were significantly correlated (Figure 1; ( E )-β-ocimene: R 2 = 0.23, P = 0.021; ( E )-α-bergamotene: R 2 = 0.50, P < 0.001).…”

Identification of Semiochemicals from Cowpea, Vigna unguiculata, for Low-input Management of the Legume Pod Borer, Maruca vitrata

“…Interestingly, in this case, S. frugiperda moths were attracted by conspecificinduced plant volatiles, especially DMNT, which highlights the fact that HIPVs play different roles in different plant-insect interactions, i.e. the effect of plant volatiles is contextdependent (He et al 2019).…”

Strigolactone signaling regulates specialized metabolism in tobacco stems and interactions with stem-feeding herbivores

“…Three additional suites of transgenic lines in which the key components of the SL and KAR signaling pathways, including D14, CCD7, and KAI2 genes (S2A and S2B Fig), were silenced by RNAi were generated (Fig 1A and 1C). For each silencing construct, we selected two independent transgenic lines, which harbored a single complete insertion of the inverted repeat RNAi construct, as verified by several NanoString probes (S2C-S2E Fig) [42]. A transgenic line transformed with an empty vector (EV) was used as control plants [11].…”

“…T 2 plants were used in all experiments. The number of insertion copies as well as the fidelity of the insertion (over-reads and truncations) were evaluated by NanoString [42]. In brief, DNA extracted from individual transgenic plants was used for NanoString to detect the content of inserted fragments according to the designed probes.…”

“…A published single-copy insertion of the stably transformed line (ago8) was used as a positive control. The single and complete T-DNA insertion in both max2#1 and max2#2 plants was validated by using NanoStrings nCounter technology as described in [42]. Briefly, TNOS+LB_1, hptII_3, PNOS_1, P35S_1, and T35S_1 (blue) are used to evaluate single and complete T-DNA insertions.…”