An ecogenomic analysis of herbivore‐induced plant volatiles in Brassica juncea

Upon herbivore feeding, plants emit complex bouquets of induced volatiles that may repel insect herbivores as well as attract parasitoids or predators. Due to differences in the temporal dynamics of individual components, the composition of the herbivore‐induced plant volatile (HIPV) blend changes with time. Consequently, the response of insects associated with plants is not constant either. Using Brassica juncea as the model plant and generalist Spodoptera spp. larvae as the inducing herbivore, we investigated herbivore and parasitoid preference as well as the molecular mechanisms behind the temporal dynamics in HIPV emissions at 24, 48 and 72 h after damage. In choice tests, Spodoptera litura moth preferred undamaged plants, whereas its parasitoid Cotesia marginiventris favoured plants induced for 48 h. In contrast, the specialist Plutella xylostella and its parasitoid C. vestalis preferred plants induced for 72 h. These preferences matched the dynamic changes in HIPV blends over time. Gene expression analysis suggested that the induced response after Spodoptera feeding is mainly controlled by the jasmonic acid pathway in both damaged and systemic leaves. Several genes involved in sulphide and green leaf volatile synthesis were clearly up‐regulated. This study thus shows that HIPV blends vary considerably over a short period of time, and these changes are actively regulated at the gene expression level. Moreover, temporal changes in HIPVs elicit differential preferences of herbivores and their natural enemies. We argue that the temporal dynamics of HIPVs may play a key role in shaping the response of insects associated with plants.     

稻飞虱卵期寄生蜂稻虱缨小蜂引诱剂的筛选与田间试验(英文)

植食性昆虫的天敌能够利用虫害诱导的挥发物进行有效的寄主或猎物定位。为了开发稻飞虱卵期天敌稻虱缨小蜂Anagrus nilaparvatae Pang et Wang的引诱剂,分别在室内和室外检测了多种褐飞虱诱导的水稻挥发物组分对褐飞虱卵期天敌稻虱缨小蜂的引诱作用。Y型嗅觉仪实验结果表明,5种单一化合物,Z-3-己烯乙酸酯,1-戊烯基-3-醇,Z-3-己烯醛,芳樟醇和水杨酸甲酯,以及3种混合物,水杨酸甲酯+Z-3-己烯醛,Z-3-己烯醛+Z-3-己烯乙酸酯+芳樟醇,水杨酸甲酯+Z-3-己烯醛+Z-3-己烯乙酸酯+芳樟醇,对稻虱缨小蜂具有明显引诱作用。田间试验表明,3种单一化合物,Z-3-己烯乙酸酯,Z-3-己烯醛和芳樟醇,以及一种混合物,水杨酸甲酯+Z-3-己烯醛+Z-3-己烯乙酸酯+芳樟醇,能明显提高稻虱缨小蜂对褐飞虱卵的寄生作用。这些结果对于改善褐飞虱治理具有重要的意义。     

Plant apocarotenoids: from retrograde signaling to interspecific communication

Carotenoids are isoprenoid compounds synthesized by all photosynthetic and some non-photosynthetic organisms. They are essential for photosynthesis and contribute to many other aspects of a plant's life. The oxidative breakdown of carotenoids gives rise to the formation of a diverse family of essential metabolites called apocarotenoids. This metabolic process either takes place spontaneously through reactive oxygen species or is catalyzed by enzymes generally belonging to the CAROTENOID CLEAVAGE DIOXYGENASE family. Apocarotenoids include the phytohormones abscisic acid and strigolactones (SLs), signaling molecules and growth regulators. Abscisic acid and SLs are vital in regulating plant growth, development and stress response. SLs are also an essential component in plants’ rhizospheric communication with symbionts and parasites. Other apocarotenoid small molecules, such as blumenols, mycorradicins, zaxinone, anchorene, β-cyclocitral, β-cyclogeranic acid, β-ionone and loliolide, are involved in plant growth and development, and/or contribute to different processes, including arbuscular mycorrhiza symbiosis, abiotic stress response, plant–plant and plant–herbivore interactions and plastid retrograde signaling. There are also indications for the presence of structurally unidentified linear cis-carotene-derived apocarotenoids, which are presumed to modulate plastid biogenesis and leaf morphology, among other developmental processes. Here, we provide an overview on the biology of old, recently discovered and supposed plant apocarotenoid signaling molecules, describing their biosynthesis, developmental and physiological functions, and role as a messenger in plant communication.     

Volatile flavour components of mango fruit

An essence of fresh Venezuelan mango fruit obtained by well-established procedures possessed the characteristic aroma of the fruit. It was analysed by GC/MS using both EI and Cl. The fruit produced a relatively small quantity of aroma volatiles (ca 60 μg/kg fresh fruit), less than that obtained from many similar tropical fruits. Terpene hydrocarbons comprised ca 68% of the sample, eight monoterpenes contributing ca 54% and four sesquiterpenes contributing ca 14%. Important constituents included α-pinene, car-3-ene, limonene, γ-terpinene, α-humulene, β-selinene, acetophenone, benzaldehyde and a dimethylstyrene. Car-3-ene (26%) was the major constituent, and on odour evaluation of separated components at an odour port during GC, the peak due to this compound was described as having an aroma of mango leaves. This compound has not previously been detected among mango volatiles. The only other component providing mango aroma was a dimethylstyrene, and this too is a new mango volatile.     

六种同域分布雌雄异株榕树挥发物多样性与系统发育一致性

植物花挥发物是维持昆虫-植物传粉互作的重要化学信号,其组成的多样性对于理解传粉昆虫与植物相互作用的形成、维持和进化具有重要意义。榕树与其传粉榕小蜂是一种专性的互惠共生关系,榕树为榕小蜂提供繁殖场所,榕小蜂为榕树传粉。而榕果雌花期（接收期）释放的特异性挥发物是维持双方相互作用的关键媒介。本研究以西双版纳地区同域分布的6种雌雄异株榕树为研究对象,用固相微萃取和气相色谱质谱联用仪对雌花期榕果的挥发物组成进行了分析。共发现77种化合物,包含脂肪酸类衍生物6种、单萜类化合物16种、倍半萜类衍生物50种和芳香族化合物5种,不同化合物对挥发物距离差异性的贡献率依次是：对甲基苯甲醚（4-methylanisole,2.15）、β-罗勒烯（β-Ocimene,0.84）和喜沙木烯（Prezizaene,0.73）。不同物种间挥发物组成有显著的差异,且挥发物的差异与榕树系统发育距离具有正相关性,但同一物种不同性别间的挥发物组成上没有显著的差异。本研究中发现雌雄异株榕树挥发物组成具有多样性高、种内性别间相似、种间差异大,系统发育一致性的特点,上述特点在榕树物种分化以及维持雌雄异株榕树繁殖的化学通讯机制中可能发挥着关键作用。     

一种南海海绵(Acanthella sp.)的化学成分研究

从中国南海海绵(Acanthella sp．)中分离得到了11个有机化合物。应用现代波谱技术和X-衍射分析,确定其结构分别为( )-α-amuurolene(I),(1R,6S,7S,10S)-10-isothiocyanato-4-amorphene(Ⅱ),acanthene B(Ⅲ),isothiocyanate 1(Ⅳ),( )-10(R)-isothiocyanatoalloaromadendrane(V),axisordtrile-3(Ⅵ),kalihinene(Ⅶ),kalihiolA(Ⅷ),胆甾醇(Ⅸ),麦角甾醇(Ⅹ)和麦角甾-6,22-二烯-5,8-环二氧-3-醇(Ⅵ)。其中化合物Ⅱ-Ⅷ是首次从中国海洋生物中分离得到的异腈萜类化合物。     

Identification and characterization of CYP79D6v4, a cytochrome P450 enzyme producing aldoximes in black poplar (Populus nigra)

After herbivore feeding, poplar trees produce complex volatile blends containing terpenes, green leaf volatiles, aromatics, and nitrogen-containing compounds such as aldoximes and nitriles. It has been shown recently that volatile aldoximes released from gypsy moth (Lymantria dispar) caterpillar-damaged black poplar (Populus nigra) trees attract parasitoids that are caterpillar enemies. In western balsam poplar (P. trichocarpa), volatile aldoximes are produced by 2 P450 monooxygenases, CYP79D6v3 and CYP79D7v2. A gene fragment with high similarity to CYP79D6/7 was recently shown to be upregulated in herbivore-damaged leaves of P. nigra. In the present study we report the cloning and characterization of this gene, designated as CYP79D6v4. Recombinant CYP79D6v4 was able to convert different amino acids into the corresponding aldoximes, which were also found in the volatile blend of P. nigra. Thus, CYP79D6v4 is most likely involved in herbivore-induced aldoxime formation in black poplar.     

Floral volatiles controlling ant behaviour

1 . Ants show complex interactions with plants, both facultative and mutualistic, ranging from grazers through seed predators and dispersers to herders of some herbivores and guards against others. But ants are rarely pollinators, and their visits to flowers may be detrimental to plant fitness.
2 . Plants therefore have various strategies to control ant distributions, and restrict them to foliage rather than flowers. These 'filters' may involve physical barriers on or around flowers, or 'decoys and bribes' sited on the foliage (usually extrafloral nectaries - EFNs). Alternatively, volatile organic compounds (VOCs) are used as signals to control ant behaviour, attracting ants to leaves and/or deterring them from functional flowers. Some of the past evidence that flowers repel ants by VOCs has been equivocal and we describe the shortcomings of some experimental approaches, which involve behavioural tests in artificial conditions.
3 . We review our previous study of myrmecophytic acacias, which used in situ experiments to show that volatiles derived from pollen can specifically and transiently deter ants during dehiscence, the effects being stronger in ant-guarded species and more effective on resident ants, both in African and Neotropical species. In these plants, repellence involves at least some volatiles that are known components of ant alarm pheromones, but are not repellent to beneficial bee visitors.
4 . We also present new evidence of ant repellence by VOCs in temperate flowers, which is usually pollen-based and active on common European ants. We use these data to indicate that across a wide range of plants there is an apparent trade-off in ant-controlling filter strategies between the use of defensive floral volatiles and the alternatives of decoying EFNs or physical barriers.     

Great tits (Parus major) flexibly learn that herbivore‐induced plant volatiles indicate prey location: An experimental evidence with two tree species

1. When searching for food, great tits (Parus major) can use herbivore‐induced plant volatiles (HIPVs) as an indicator of arthropod presence. Their ability to detect HIPVs was shown to be learned, and not innate, yet the flexibility and generalization of learning remain unclear.
2. We studied if, and if so how, naïve and trained great tits (Parus major) discriminate between herbivore‐induced and noninduced saplings of Scotch elm (Ulmus glabra) and cattley guava (Psidium cattleyanum). We chemically analyzed the used plants and showed that their HIPVs differed significantly and overlapped only in a few compounds.
3. Birds trained to discriminate between herbivore‐induced and noninduced saplings preferred the herbivore‐induced saplings of the plant species they were trained to. Naïve birds did not show any preferences. Our results indicate that the attraction of great tits to herbivore‐induced plants is not innate, rather it is a skill that can be acquired through learning, one tree species at a time.
4. We demonstrate that the ability to learn to associate HIPVs with food reward is flexible, expressed to both tested plant species, even if the plant species has not coevolved with the bird species (i.e., guava). Our results imply that the birds are not capable of generalizing HIPVs among tree species but suggest that they either learn to detect individual compounds or associate whole bouquets with food rewards.