Christer Löfstedt

Sex pheromones are environmentally friendly alternatives to traditional insecticides for pest control. The high synthesis cost, however, has restricted large-scale application. Plant-based biofactories provide a promising, sustainable route for cost-effective production that could facilitate the broader use of pheromone-based pest control. Mating disruption of the yellow peach moth, Conogethes punctiferalis –a serious pest of fruit trees and field crops in East Asia–can be achieved using ( E )-10-hexadecenal and ( Z )-10-hexadecenal, two components of its sex pheromone. To enable rational reconstruction of the biosynthetic pathway towards these unusual fatty acid derivatives in heterologous production systems, we first elucidated their biosynthesis by combining in vivo labeling experiments, transcriptomics and functional characterization of candidate desaturase and reductase genes using Nicotiana benthamiana and yeast expression systems. We identified a rare Δ10 fatty acyl desaturase that catalyzes the production of both ( E )- 10- and ( Z )-10-hexadecenoic acids, along with a downstream fatty acyl reductase with higher activity on the E isomer. We further introduced this Δ10 desaturase together with an acyl-ACP thioesterase-1 into Camelina sativa to redirect seed lipid metabolism towards the accumulation of the pheromone precursor fatty acids. After four generations of selection, we obtained stably inherited Camelina lines accumulating up to 4.7% of target fatty acids in total seed lipids, with individual seeds containing up to 8.3 μg, without significant effects on plant growth or seed viability. These findings demonstrate how elucidating moth pheromone biosynthetic pathways can support the development of sustainable biotechnological production systems for pheromone-based pest management.

Sex pheromones are eco‐friendly agents to control pest insects. Yet, the cost of synthetic pheromone production has restricted their use essentially to high value crops. Plant‐based bioproduction of pheromone compounds offers a promising and sustainable alternative, opening up for the deployment of pheromone‐mediated pest control also in row crops. The rice leaffolder Cnaphalocrocis medinalis uses C18 pheromone compounds and is a major rice pest in South China. We demonstrate that the fatty acid precursor of the main C18 pheromone component of Cnaphalocrocis medinalis , ( Z )‐13‐octadecenal, can be biotechnologically produced using the oilseed crop Camelina sativa . First, we used deuterium‐labelling to establish an elongation‐based pathway for pheromone precursor formation from hexadecanoic (palmitic) acid via desaturation to ( Z )‐11‐hexadecenoic acid and elongation to ( Z )‐13‐octadecenoic acid. Using transient expression in Nicotiana benthamiana , we identified a minimal pathway consisting of a ∆11 desaturase ( CmedDES1 ), an elongase ( CmedELO1 ), and a fatty acyl reductase ( CmedFAR2 ) for the heterologous biosynthesis of long‐chain monounsaturated C18 precursors in planta . Co‐expression of the insect desaturases CmedDES1 or CsupYPAQ with the Camelina elongase CsaKCS1 in Nicotiana benthamiana resulted in higher production of Z13‐18 products compared to co‐expression with insect elongases. We finally engineered Camelina sativa seeds through seed‐specific co‐expression of the Z11‐16‐forming insect desaturase CsupYPAQ and CsaKCS1 elongase, enabling the accumulation of C18 fatty acid pheromone precursors. Our study paves the way for sustainable production of the sex pheromone of Cnaphalocrocis medinalis and other C18 monounsaturated pheromone precursors for crop protection.

Sex pheromones are eco-friendly agents to control pest insects. Yet, the cost of synthetic pheromone production has restricted their use essentially to high value crops. Plant-based bioproduction of pheromone compounds offers a promising and sustainable alternative, opening up for the deployment of pheromone-mediated pest control also in row crops. The rice leaffolder Cnaphalocrocis medinalis uses C18 pheromone compounds and is a major rice pest in South China. We demonstrate that the fatty acid precursor of the main C18 pheromone component of C. medinalis , ( Z )-13-octadecenal, can be biotechnologically produced using the oilseed crop Camelina sativa . First, we used deuterium-labelling to establish an elongation-based pathway for pheromone precursor formation from hexadecanoic (palmitic) acid via desaturation to ( Z )-11-hexadecenoic acid and elongation to ( Z )-13-octadecenoic acid. Using transient expression in Nicotiana benthamiana , we identified a minimal pathway consisting of a Δ11 desaturase ( CmedDES1 ), an elongase ( CmedELO1 ), and a fatty acyl reductase ( CmedFAR2 ) for the heterologous biosynthesis of long-chain pheromone monounsaturated C18 precursors in planta. Co-expression of the insect desaturases CmedDES1 or CsupYPAQ with the Camelina elongase CsaKCS1 in Nicotiana benthamiana resulted in higher production of Z13-18 products compared to co-expression with insect elongases. We finally engineered Camelina sativa seeds through seed-specific co-expression of the Z11-16-forming insect desaturase CsupYPAQ and CsaKCS1 elongase, enabling the accumulation of C18 fatty acid pheromone precursors. Our study paves the way for sustainable production of the sex pheromone of C. medinalis and other C18 monounsaturated pheromone precursors for crop protection.

Currant, and in particular blackcurrant, Ribes nigrum , is widely grown in Europe. It is the host of a number of pest insects, but their occurrence and the damage they cause vary geographically. In northern Europe, three lepidopteran species, the currant shoot borer ( Lampronia capitella ), the currant clearwing ( Synanthedon tipuliformis ), and the currant bud moth ( Euhyponomeutoides albithoracellus ), are particularly damaging and sometimes cause decreased plant vigour and drastic yield losses. With fewer insecticides approved for use and with an increased interest in organic production of currants, the need for alternative methods to control these moths is urgent. We here applied pheromone‐based mating disruption in small and sometimes well isolated plantations in Finland, Norway and Sweden against the three pests using 15–25 g of active ingredients and 300 dispensers per ha. A strong trap shutdown effect, up to 100%, was recorded for the currant clearwing and the currant bud moth, but no effect on the most widespread species, the currant shoot borer, was noted. After 1 year of treatment, however, it was not possible to detect any significant effect on the damage level or on the future adult population size of the pests. We conclude that for the currant clearwing and the currant bud moth, mating disruption is likely to work with higher pheromone doses or modified dispenser density, whereas the reason behind the lack of effect on the currant shoot borer needs to be addressed by new experiments and observations of behaviour.

The currant bud moth, Euhyponomeutoides albithoracellus , the currant shoot borer, Lampronia capitella and the currant clearwing, Synanthedon tipuliformis , are destructive pests on currants in the Nordic countries, but detailed information about their relative abundance in commercial crop fields is lacking. We used pheromone‐baited monitoring traps to analyse the presence and flight period of the three species in 28 commercial black currant fields in Finland, Norway and Sweden during 4 years. We also estimated moth‐induced damage in the same fields and analysed within‐ and between‐generation relationships of catches and damage to find patterns to predict current and future pest pressures. At least two of the species were found at all sites. The shoot borer was the most widespread and abundant species, followed by the clearwing, which was relatively common at all sites except in northern Sweden, whereas the bud moth was not detected at all in Norway and southern Sweden. Geographic variation in flight phenology was observed for both the shoot borer and the clearwing. We found a significant positive correlation in all between‐year analyses of damage and in most between‐year analyses of catches, but a less consistent pattern when relating catches to damage within and between generations. Combining catch and damage data may be a useful tool to predict future overall infestation levels of the three pests in black currant fields in the Nordic countries.

Regeneration of Norway spruce, Picea abies, forests is to a large extent depending on the production of seeds from high quality plus trees in orchards. However, the seed yield is variable and unpredictable due to weather, pest insects and diseases. Thus, more knowledge is needed to improve planning of harvest and mitigation of pests and diseases to secure future forest regeneration. In this study, we used pheromone traps and cone inventory to document the phenology and population trends of three important lepidopteran seed and cone consumers, viz. the spruce seed moth, Cydia strobilella, the spruce coneworm, Dioryctria abietella and the cloaked pug, Eupithecia abietaria, in six south Swedish orchards over 6 years. The flight period of C. strobilella was concentrated in May, whereas D. abietella had an extended flight period from May to October, and E. abietaria mainly flew in June and early July. Population densities measured by trap catch and cone density fluctuated between years and orchards, despite these were located within 74 km of each other. For C. strobilella, but not for D. abietella, there was a significant relationship between the number of males captured per trap and the number of larvae per ha or the proportion of infested cones in the subsequent generation. No significant relationships occurred between larval density and trap catch the following year (within generation) for any of the species. Notably, the trap catches were high also after years almost void of breeding material, that is, cones. Our results indicate that we still lack information on several parameters essential for reliable predictions of population trends, such as prolonged diapause, winter survival and the presence and abundance of natural enemies.

The sense of smell is a central sensory modality of most terrestrial species. However, our knowledge of olfaction is based on vertebrates and insects. In contrast, little is known about the chemosensory world of spiders and nothing about how they perform olfaction despite their important ecological role. The orb-weaving spider Argiope bruennichi lends itself to an in-depth study on olfaction as it is one of the few spider species whose volatile sex pheromone, emitted by females to attract males, is known. We combined ultrastructural and electrophysiological analyses and found that previously overlooked sensilla with wall pores are abundant on all walking legs of A. bruennichi males. We compared the ultrastructure of these wall-pore sensilla with those known to perform olfaction in insects, exploring similarities and differences. Electrophysiological single sensillum recordings demonstrated that the wall-pore sensilla in A. bruennichi respond highly sensitive and in a concentration-dependent manner to the sex pheromone. Our study demonstrates male-specific sensilla for detecting signaling females, whereas females and subadult males are devoid of wall pore sensilla. In a preliminary comparative morphological analysis using 19 species from 16 spider families, we found that wall-pore sensilla occur in male spiders from most, but not in basally branching clades or in Salticids, suggesting that wall-pore sensilla evolved at least once within spiders and were lost at least once. This research significantly expands our knowledge of the sensory ecology of spiders, will stimulate studies on the diversity and function of sensilla, as well as studies on the evolution of olfaction in arthropods.

Aphids cause massive agricultural losses through direct damage or as pathogen vectors. Control often relies on insecticides, which are expensive and not selective. An interesting alternative is to use aphid sex pheromones nepetalactone (NON) and nepetalactol (NOL) to interfere with aphid mating or attract aphid predators. Here, we explore production of these compounds in plants, as their precursors can be derived from mevalonate (MVA) and methylerythritol phosphate (MEP) pathways. By introducing six genes, including a major latex protein‐like (MLPL) enzyme, we engineered a functional nepetalactol biosynthetic pathway into plants. Transient expression of these enzymes in N. benthamiana caused production of nepetalactone, without the need for external supplementation with substrates. Targeting all six enzymes into the chloroplast appeared to result in higher NON yields than just chloroplast‐targeting the first two enzymes. We could not detect NOL, suggesting it is rapidly oxidised to NON. In addition, we produced NON in stably transformed Camelina sativa (Camelina) lines. Interestingly, the specific NON enantiomer was different in N. benthamiana compared to in Camelina, indicating the value of different platforms for producing specific isoforms. This opens possibilities for using plants as green factories of pheromones for baits or as pheromone dispensers that interfere with insect behaviour.