The Basic/Helix-Loop-Helix Transcription Factor Family Gene RcbHLH112 Is a Susceptibility Gene in Gray Mould Resistance of Rose (Rosa Chinensis).

The basic/helix-loop-helix (bHLH) family is a major family of transcription factors in plants. Although it has been reported that bHLH plays a defensive role against pathogen infection in plants, there is no comprehensive study on the bHLH-related defence response in rose (Rosa sp.). In this study, a genome-wide analysis of bHLH family genes (RcbHLHs) in rose was carried out, including their phylogenetic relationships, gene structure, chromosome localization and collinearity analysis. Via phylogenetic analysis, a total of 121 RcbHLH genes in the rose genome were divided into 21 sub-groups. These RcbHLHs are unevenly distributed in all 7 chromosomes of rose. The occurrence of gene duplication events indicates that whole-genome duplication and segmental duplication may play a key role in gene duplication. Ratios of non-synonymous to synonymous mutation frequency (Ka/Ks) analysis showed that the replicated RcbHLH genes mainly underwent purification selection, and their functional differentiation was limited. Gene expression analysis showed that 46 RcbHLHs were differentially expressed in rose petals upon B. cinerea infection. It is speculated that these RcbHLHs are candidate genes that regulate the response of rose plants to B. cinerea infection. Virus-induced gene silencing (VIGS) confirmed that RcbHLH112 in rose is a susceptibility factor for infection with B. cinerea. This study provides useful information for further study of the functions of the rose bHLH gene family.

Two jasmonic acid carboxyl methyltransferases in Gossypium hirsutum involved in MeJA biosynthesis may contribute to plant defense.

Jasmonic acid (JA) and methyl jasmonate (MeJA), the crucial plant hormones, can induce the emission of plant volatiles and regulate the behavioral responses of insect pests or their natural enemies. In this study, two jasmonic acid carboxyl methyltransferases (JMTs), GhJMT1 and GhJMT2, involved in MeJA biosynthesis in Gossypium. hirsutum were identified and further functionally confirmed. In vitro, recombinant GhJMT1 and GhJMT2 were both responsible for the conversion of JA to MeJA. Quantitative real-time PCR (qPCR) measurement indicated that GhJMT1 and GhJMT2 were obviously up-regulated in leaves and stems of G. hirsutum after being treated with MeJA. In gas chromatography-mass spectrometry (GC-MS) analysis, MeJA treatment significantly induced plant volatiles emission such as (E)-ß-ocimene, (Z)-3-hexenyl acetate, linalool and (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), which play vital roles in direct and indirect plant defenses. Moreover, antennae of parasitoid wasps Microplitis mediator showed electrophysiological responses to MeJA, ß-ocimene, (Z)-3-hexenyl acetate and linalool at a dose dependent manner, while our previous research revealed that DMNT excites electrophysiological responses and behavioral tendencies. These findings provide a better understanding of MeJA biosynthesis and defense regulation in upland cotton, which lay a foundation to JA and MeJA employment in agricultural pest control.

Functional characterization of a terpene synthase responsible for (E)-ß-ocimene biosynthesis identified in Pyrus betuleafolia transcriptome after herbivory.

(E)-ß-ocimene, a ubiquitous monoterpene volatile in plants, is emitted from flowers to attract pollinators and/or from vegetative tissues as part of inducible defenses mediated by complex signaling networks when plants are attacked by insect herbivores. Wild pear species Pyrus betuleafolia used worldwide as rootstock generally displays valuable pest-resistant traits and is a promising genetic resource for pear breeding. In the current study, transcriptional changes in this wild pear species infested with a polyphagous herbivore Spodoptera litura and the underlying molecular mechanisms were fully investigated. A total of 3,118 differentially expressed genes (DEGs) were identified in damaged pear leaf samples. Spodoptera litura larvae infestation activated complex phytohormonal signaling networks in which jasmonic acid, ethylene, brassinosteroids, cytokinin, gibberellic acid and auxin pathways were induced, whereas salicylic acid and abscisic acid pathways were suppressed. All DEGs associated with growth-related photosynthesis were significantly downregulated, whereas most DEGs involved in defense-related early signaling events, transcription factors, green leaf volatiles and volatile terpenes were significantly upregulated. The PbeOCS (GWHGAAYT028729), a putative (E)-ß-ocimene synthase gene, was newly identified in P. betuleafolia transcriptome. The upregulation of PbeOCS in S. litura-infested pear leaves supports a potential role for PbeOCS in herbivore-induced plant defenses. In enzyme-catalyzed reaction, recombinant PbeOCS utilized only geranyl pyrophosphate but not neryl diphosphate, farnesyl pyrophosphate or geranylgeranyl diphosphate as a substrate, producing (E)-ß-ocimene as the major product and a trace amount of (Z)-ß-ocimene. Moreover, as a catalytic product of PbeOCS, (E)-ß-ocimene showed repellent effects on larvae of S. litura in dual-choice bioassays. What is more, (E)-ß-ocimene increased mortalities of larvae in no-choice bioassays. These findings provide an overview of transcriptomic changes in wild pears in response to chewing herbivores and insights into (E)-ß-ocimene biosynthesis in pear plants, which will help elucidate the molecular mechanisms underlying pear-insect interactions.

Characterization of a Novel Insect-Induced Sesquiterpene Synthase GbTPS1 Based on the Transcriptome of Gossypium barbadense Feeding by Cotton Bollworm.

When attacked by insect herbivores, plants initiate sophisticated defenses mediated by complex signaling networks and usually release a blend of functional volatiles such as terpenes against infestation. The extra-long staple cotton Gossypium barbadense cultivated worldwide as natural textile fiber crop is frequently exposed to a variety of herbivores, such as cotton bollworm Helicoverpa armigera. However, little is known about insect-induced transcriptional changes and molecular mechanisms underlying subsequent defense responses in G. barbadense. In the current study, transcriptome changes in G. barbadense infested with chewing H. armigera larvae were investigated, and we identified 5,629 differentially expressed genes (DEGs) in the infested cotton leaves compared with non-infested controls. H. armigera feeding triggered complex signaling networks in which almost all (88 out of 90) DEGs associated with the jasmonic acid (JA) pathway were upregulated, highlighting a central role for JA in the defense responses of G. barbadense against target insects. All DEGs involved in growth-related photosynthesis were downregulated, whereas most DEGs associated with defense-related transcript factors and volatile secondary metabolism were upregulated. It was noteworthy that a terpene synthase gene in the transcriptome data, GbTPS1, was strongly expressed in H. armigera-infested G. barbadense leaves. The upregulation of GbTPS1 in qPCR analysis also suggested an important role for GbTPS1 in herbivore-induced cotton defense. In vitro assays showed that recombinant GbTPS1 catalyzed farnesyl pyrophosphate and neryl diphosphate to produce three sesquiterpenes (selinene, α-gurjunene, and ß-elemene) and one monoterpene (limonene), respectively. Moreover, these catalytic products of GbTPS1 were significantly elevated in G. barbadense leaves after H. armigera infestation, and elemene and limonene had repellent effects on H. armigera larvae in a dual-choice bioassay and increased larval mortality in a no-choice bioassay. These findings provide a valuable insight into understanding the transcriptional changes reprogramming herbivore-induced sesquiterpene biosynthesis in G. barbadense infested by H. armigera, which help elucidate the molecular mechanisms underlying plant defense against insect pests.

Modelling the current and future potential distribution of the bean bug Riptortus pedestris with increasingly serious damage to soybean.

BACKGROUND: The bean bug, Riptortus pedestris, has received intense attention in recent years because of its involvement in increasing outbreaks of staygreen syndrome in soybean (Glycine max (L.)), often causing almost 100% loss of soybean yield in China. However, for this pest of great economic importance, potential current and future distribution patterns and their underlying driving factors remain unclear. RESULTS: Maxent modelling under climate, elevation and land-use (including the distribution information of G. max) variables showed that the current potential distribution covered a vast geographic range, primarily including most parts of south, South East and east Asia. Under future environmental scenarios, suitable habitat expanded markedly. Areas that would become highly suitable for R. pedestris were primarily located in north-east China and west India. Five bioclimatic (BIO13, BIO08, BIO18, BIO02 and BIO07) and one land-use (C3 annual crops) predictors contributed approximately 95% to the modelling, and analyses of curve responses showed that to a certain extent, R. pedestris preferred relatively high temperature and precipitation. Our results indicate that a high risk of R. pedestris outbreaks is present in parts of Asia, especially in the soybean-growing regions of China, and this risk will continue in the future. CONCLUSION: The predicted distribution pattern and key regulating factors identified herein could provide a vital reference for developing pest management policies and further alleviate the incidence of staygreen syndrome in soybean. © 2022 Society of Chemical Industry.

Effects of aphid-induced semiochemicals from cover plants on Harmonia axyridis (Coleoptera: Coccinellidae).

BACKGROUND: Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an important natural enemy of aphids. Plant species and plant health conditions can affect the behavior of H. axyridis. To determine plant effects on this lady beetle, we examined beetle responses to four cover crops: coriander (Coriadrum sativum L., Apiales: Apiaceae), marigold (Tagetes erecta L., Asterales: Asteraceae), sweet alyssum (Lobularia maritima L., Brassicales: Brassicaceae), and alfalfa (Medicago sativa L., Fabales: Fabaceae). Our goal was to better understand this predator's ovipositional behavior in response to different plants and its olfactory response to the aphid-induced volatiles from these plants. RESULTS: We found that this lady beetle did not have any significant oviposition preference among the four plant species, but H. axyridis preferred to lay eggs on the lower surface of leaves, regardless of the plant species. H. axyridis females had a significant preference for aphid-infested marigolds, but were not attracted by any of the other three cover plants or marigolds without aphid damage. Compared to the uninfested marigold plants, the emission of 12 compounds significantly increased on the aphid-infested marigolds, and two of them were attractive to H. axyridis under suitable concentrations. CONCLUSION: H. axyridis did not show any significant oviposition preference among the four cover crops. Aphid-infested marigolds can attract H. axyridis. Indole and terpinen-4-ol mediated lady beetle attraction. These synomones have potential for manipulating populations of H. axyridis as a component of conservation biological control. © 2022 Society of Chemical Industry.

Haplotype-resolved genome of diploid ginger (Zingiber officinale) and its unique gingerol biosynthetic pathway.

Ginger (Zingiber officinale), the type species of Zingiberaceae, is one of the most widespread medicinal plants and spices. Here, we report a high-quality, chromosome-scale reference genome of ginger 'Zhugen', a traditionally cultivated ginger in Southwest China used as a fresh vegetable, assembled from PacBio long reads, Illumina short reads, and high-throughput chromosome conformation capture (Hi-C) reads. The ginger genome was phased into two haplotypes, haplotype 1 (1.53 Gb with a contig N50 of 4.68 M) and haplotype 0 (1.51 Gb with a contig N50 of 5.28 M). Homologous ginger chromosomes maintained excellent gene pair collinearity. In 17,226 pairs of allelic genes, 11.9% exhibited differential expression between alleles. Based on the results of ginger genome sequencing, transcriptome analysis, and metabolomic analysis, we proposed a backbone biosynthetic pathway of gingerol analogs, which consists of 12 enzymatic gene families, PAL, C4H, 4CL, CST, C3'H, C3OMT, CCOMT, CSE, PKS, AOR, DHN, and DHT. These analyses also identified the likely transcription factor networks that regulate the synthesis of gingerol analogs. Overall, this study serves as an excellent resource for further research on ginger biology and breeding, lays a foundation for a better understanding of ginger evolution, and presents an intact biosynthetic pathway for species-specific gingerol biosynthesis.

Host plants transfer induced regulation of the chemosensory genes repertoire in the alfalfa plant bug Adelphocoris lineolatus (Goeze).

The alfalfa plant bug Adelphocoris lineolatus, an economically important pest, has representative behavioral characteristics with host plants transfer. Olfactory system is essential for insects to perceive ever-changing chemical signals in the external environment, and chemosensory genes play crucial roles in signals reception and transduction. In this work, we compared the differences in chemosensory genes expression before and after host plants transfer by constructing 12 antennal transcriptomes of male and female bugs, respectively. The results showed that the expression levels of most chemosensory genes in A. lineolatus changed to adapt to the transformation of the hosts plant. More remarkable, female bugs had more up-regulated chemosensory genes than males. Differentially expressed genes (DEGs) analysis revealed three odorant binding proteins (OBPs), three chemosensory proteins (CSPs), eight odorant receptors (ORs) and one ionotropic receptor (IR) showed significant differences when the host plant transferred. There were complex characteristics of up- and down- regulated genes in male and female adults, among which OBP19 showed higher expression in females exposing to the new host plant alfalfa, suggesting this OBP may be associated with the localization of the oviposition site. The OR54 and OR82 were up-regulated in both genders, indicating their possible roles in recognizing some alfalfa-specific volatiles. These findings will provide valuable insights in biological functions of chemosensory genes in A. lineolatus and facilitate the development of new targets for novel strategies to control the alfalfa plant bug and other herbivores.

Engineering Nicotiana tabacum for the de novo biosynthesis of DMNT to regulate orientation behavior of the parasitoid wasps Microplitis mediator.

BACKGROUND: (E)-4,8-dimethylnona-1,3,7-triene (DMNT), one of the homoterpenes, is thought to contribute to plant indirect defense against insect herbivores. DMNT-enriched plants have great application potential to regulate insect behavior in the 'push & pull' strategy of pest management. However, de novo biosynthesis of DMNT in plants without a homoterpene metabolic pathway in their wild type is still not achieved, and the role of DMNT played in these plants and their interacted insects remains unclear. RESULTS: Cytochrome P450s and terpene synthases involved in homoterpenes biosynthesis in cotton plants were employed to generate DMNT-releasing tobacco plants. Single GhTPS14 transgenic Nicotiana tabacum only emitted (E)-nerolidol, the precursor of DMNT. Transgenic tobaccos expressing single GhCYP82Ls were unable to produce DMNT or TMTT, while DMNT was detected when exogenous (E)-nerolidol was added. Compared to wild-type plants, only co-expression of GhCYP82Ls and GhTPS14 in transgenic tobaccos triggered the constitutive release of single-component DMNT. Furthermore, DMNT-emitting transgenic tobacco plants, whether infested with Helicoverpa armigera larvae or not, significantly incited orientation behavior of parasitoid wasps Microplitis mediator. CONCLUSION: Wild type N. tabacum plants have no DMNT metabolic pathway. DMNT could be de novo biosynthesized via co-expression of GhCYP82Ls and GhTPS14. What is more, the parasitoid wasp M. mediator could be recruited by DMNT-releasing transgenic tobaccos, especially by H. armigera-infested transgenic tobaccos, suggesting the potential roles of engineered N. tabacum in regulating the behavioral preference of M. mediator.

Prior Experience with Food Reward Influences the Behavioral Responses of the Honeybee Apis mellifera and the Bumblebee Bombus lantschouensis to Tomato Floral Scent.

Bee responses to floral scent are usually influenced by both innate biases and prior experience. Honeybees are less attracted than bumblebees to tomato flowers. However, little is known about how tomato floral scent regulates the foraging behaviors of honeybees and bumblebees. In this study, the foraging behaviors of the honeybee Apis mellifera and the bumblebee Bombus lantschouensis on tomato flowers in greenhouses were investigated. Whether the two bee species exhibit different responses to tomato floral scent and how innate biases and prior experience influence bee choice behavior were examined. In the greenhouses, honeybees failed to collect pollen from tomato flowers, and their foraging activities decreased significantly over days. Additionally, neither naïve honeybees nor naïve bumblebees showed a preference for tomato floral scent in a Y-tube olfactometer. However, foraging experience in the tomato greenhouses helped bumblebees develop a strong preference for the scent, whereas honeybees with foraging experience continued to show aversion to tomato floral scent. After learning to associate tomato floral scent with a sugar reward in proboscis extension response (PER) assays, both bee species exhibited a preference for tomato floral scent in Y-tube olfactometers. The findings indicated that prior experience with a food reward strongly influenced bee preference for tomato floral scent.

The male-produced aggregation pheromone of the bean flower thrips Megalurothrips usitatus in China: identification and attraction of conspecifics in the laboratory and field.

BACKGROUND: Thrips, Megalurothrips usitatus, usually display aggregation behavior, which is probably mediated by a male-produced aggregation pheromone. Aggregation pheromones are species-specific, and can be used to develop commercial lures for monitoring and mass-trapping of pests. The active components of the aggregation pheromone for four thrips species have been identified. However, the components of M. usitatus-produced aggregation pheromone are still not clear. RESULT: Y-tube olfactometer assays showed that both male and virgin female M. usitatus were significantly attracted to male but not female volatiles. This was additionally supported by electroantennogram (EAG) assays. Coupled gas chromatography-electroantennogram detection (GC-EAD) showed that one component of male-specific odors elicited a significant electrophysiological response. This compound was characterized as (2E,6E)-farnesyl acetate, which is structurally different from the active components of the aggregation pheromones of other reported thrips species. Electroantennal responses of M. usitatus increased with increasing doses of synthetic (2E,6E)-farnesyl acetate. Additionally, this compound significantly attracted adults in laboratory behavioral bioassays. Under field conditions, sticky traps with synthetic (2E,6E)-farnesyl acetate caught 1.5-7-fold more M. usitatus than controls, and this effect of the compound at a dose of 60 µg lasted at least 6 days. CONCLUSION: (2E,6E)-Farnesyl acetate was identified as the male-produced aggregation pheromone of M. usitatus. It could attract this thrips species under laboratory and field conditions, suggesting considerable potential as a commercial application to control M. usitatus populations. © 2020 Society of Chemical Industry.

Overexpression of the caryophyllene synthase gene GhTPS1 in cotton negatively affects multiple pests while attracting parasitoids.

BACKGROUD: Volatile terpenes can act as ecological signals to affect insect behavior. It has been proposed that the manipulation of terpenes in plants can help to control herbivore pests. In order to investigate the potential pest management function of (E)-ß-caryophyllene in cotton plants, the (E)-ß-caryophyllene synthase gene (GhTPS1) was inserted into Gossypium hirsutum variety R15 to generate overexpression lines. RESULTS: Four GhTPS1-transgenic lines were generated, and GhTPS1 expression in transgenic L18 and L46 lines was 3-5-fold higher than in R15 plants. The transgenic L18 and L46 lines also emitted significantly more (E)-ß-caryophyllene than R15. In laboratory bioassays, L18 and L46 plants reduced pests Apolygus lucorum, Aphis gossypii and Helicoverpa armigera, and attracted parasitoids Peristenus spretus and Aphidius gifuensis, but not Microplitis mediator. In open-field trials, L18 and L46 plants reduced A. lucorum, Adelphocoris suturalis and H. armigera, but had no significant effects on predators. CONCLUSION: Our findings suggest that L18 and L46 plants reduce several major hemipteran and lepidopteran cotton pests, whereas, two parasitoids P. spretus and A. gifuensis, were attracted by L18 and L46 plants. This study shows that overexpressing GhTPS1 in cotton may help to improve pest management in cotton fields. © 2019 Society of Chemical Industry.

Behavioral thermoregulation in Locusta migratoria manilensis (Orthoptera: Acrididae) in response to the entomopathogenic fungus, Beauveria bassiana.

Insects such as locusts and grasshoppers can reduce the effectiveness of pathogens and parasites by adopting different defense strategies. We investigated the behavioral thermopreference of Locusta migratoria manilensis (Meyen) (Orthoptera: Acrididae) induced by the fungus Beauveria bassiana, and the impact this behavior had on the fungal mycosis under laboratory conditions. By basking in higher temperature locations, infected nymphs elevated their thoracic temperature to 30-32.6 °C, which is higher than the optimum temperature (25°C) for B. bassiana conidial germination and hyphal development. A minimum thermoregulation period of 3 h/day increased survival of infected locusts by 43.34%. The therapeutic effect decreased when thermoregulation was delayed after initial infection. The fungus grew and overcame the locusts as soon as the thermoregulation was interrupted, indicating that thermoregulation helped the insects to cope with infection but did not completely rid them of the fungus. A significant enhancement in the number of haemocytes was observed in infected thermoregulating locusts, reaching levels that were even higher than those observed in the controls. In contrast, haemocyte concentration was severely reduced in infected insects that did not thermoregulate. In infected non-thermoregulating locusts, the reduction in haemocyte number was accompanied by an increase in fungal blastospore concentration that was obvious in the haemolymph by day four. In contrast, no circulating blastospores were found in the haemolymph of infected thermoregulating locusts three days post-inoculation. We also examined the phagocytic activity of infected insects in vivo by using fluorescein isothiocyanate (FITC)-labelled silica beads. The proportion of beads that was engulfed by haemocytes in infected, thermoregulating insects was similar to that in the controls throughout the experiment, whereas the rate of phagocytosis in infected, non-thermoregulating insects progressively decreased after infection. These findings demonstrated that behavioural thermoregulation can adversely affect B. bassiana mycosis in infected L. migratoria manilensis, thereby limiting the development of lethal entomopathogenic fungi in locusts. This is apparently accomplished through an increase in the levels of haemocytes, leading to greater phagocytic activity under certain environmental conditions.

The terpene synthase gene family in Gossypium hirsutum harbors a linalool synthase GhTPS12 implicated in direct defence responses against herbivores.

Herbivore-induced terpenes have been reported to function as ecological signals in plant-insect interactions. Here, we showed that insect-induced cotton volatile blends contained 16 terpenoid compounds with a relatively high level of linalool. The high diversity of terpene production is derived from a large terpene synthase (TPS) gene family. The TPS gene family of Gossypium hirsutum and Gossypium raimondii consist of 46 and 41 members, respectively. Twelve TPS genes (GhTPS4-15) could be isolated, and protein expression in Escherichia coli revealed catalytic activity for eight GhTPS. The upregulation of the majority of these eight genes additionally supports the function of these genes in herbivore-induced volatile biosynthesis. Furthermore, transgenic Nicotiana tabacum plants overexpressing GhTPS12 were generated, which produced relatively large amounts of (3S)-linalool. In choice tests, female adults of Helicoverpa armigera laid fewer eggs on transgenic plants compared with non-transformed controls. Meanwhile, Myzus persicae preferred feeding on wild-type leaves over leaves of transgenic plants. Our findings demonstrate that transcript accumulation of multiple TPS genes is mainly responsible for the production and diversity of herbivore-induced volatile terpenes in cotton. Also, these genes might play roles in plant defence, in particular, direct defence responses against herbivores.

Identification and functional analysis of two P450 enzymes of Gossypium hirsutum involved in DMNT and TMTT biosynthesis.

The homoterpenes (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) are major herbivore-induced plant volatiles that can attract predatory or parasitic arthropods to protect injured plants from herbivore attack. In this study, DMNT and TMTT were confirmed to be emitted from cotton (Gossypium hirsutum) plants infested with chewing caterpillars or sucking bugs. Two CYP genes (GhCYP82L1 and GhCYP82L2) involved in homoterpene biosynthesis in G. hirsutum were newly identified and characterized. Yeast recombinant expression and enzyme assays indicated that the two GhCYP82Ls are both responsible for the conversion of (E)-nerolidol to DMNT and (E,E)-geranyllinalool to TMTT. The two heterologously expressed proteins without cytochrome P450 reductase fail to convert the substrates to homoterpenes. Quantitative real-time PCR (qPCR) analysis suggested that the two GhCYP82L genes were significantly up-regulated in leaves and stems of G. hirsutum after herbivore attack. Subsequently, electroantennogram recordings showed that electroantennal responses of Microplitis mediator and Peristenus spretus to DMNT and TMTT were both dose dependent. Laboratory behavioural bioassays showed that females of both wasp species responded positively to DMNT and males and females of M. mediator could be attracted by TMTT. The results provide a better understanding of homoterpene biosynthesis in G. hirsutum and of the potential influence of homoterpenes on the behaviour of natural enemies, which lay a foundation to study genetically modified homoterpene biosynthesis and its possible application in agricultural pest control.

Efficiency of Trichome-Based Plant Defense in Phaseolus vulgaris Depends on Insect Behavior, Plant Ontogeny, and Structure.

Plant trichomes often function as physical barriers in preventing arthropod feeding and oviposition. Even though insects are frequently reported being entrapped and killed by trichome traps, the actual trapping behavior has not yet been described in detail. Capture experiments showed that capture efficiency during the plant's vegetative stage was considerably higher than in the fruiting and cotyledon stages. The ventral surface of the leaf was more effective in trapping flies than other parts of the plant. Capture-events monitoring showed that the mouthparts, legs, and ovipositor of Liriomyza trifolii adults are the body parts involved in entrapment by surface trichomes on Phaseolus vulgaris plants, and subsequently, deter their ability to feed, walk, and oviposit. Of the three main body parts normally affected, mouthparts was found to be the body part most susceptible to the trichomes. Entrapments were most often caused by landing, followed by puncturing or feeding, and occasionally by walking or fighting. Using scanning electron microscopy (SEM) and optical microscopy, we determined the susceptible positions of each body part and found that the flies were all trapped by hooked trichomes. This study revealed the process by which leafminer flies are entrapped by surface trichomes of the host plant and evaluated the capture efficiency. The results will contribute to our understanding of physical defenses against herbivores.

TPS46, a Rice Terpene Synthase Conferring Natural Resistance to Bird Cherry-Oat Aphid, Rhopalosiphum padi (Linnaeus).

Plant terpene synthases (TPSs) are key enzymes responsible for terpene biosynthesis, and can play important roles in defense against herbivore attack. In rice, the protein sequence of TPS46 was most closely related to maize TPS10. However, unlike maize tps10, tps46 was also constitutively expressed in rice even in the absence of herbivore attack. Potential roles or constitutive emissions of specific volatiles may due to the constitutive expressions of tps46 in rice. Therefore, in the present study, RNA interference (Ri) and overexpression (Oe) rice lines were generated to investigate the potential function of TPS46 in Oryza sativa sp. japonica. Interestingly, the rice plants become more susceptible to Rhopalosiphum padi when expression of tps46 was silenced compared with Wt in greenhouse conditions. Artificial infestation bioassays further confirmed that Ri rice lines were susceptible to R. padi, whereas Oe rice lines were repellent to R. padi. Based on GC-MS and ToF-MS analysis, a total of eight volatile products catalyzed by TPS46 in rice were identified. Among them, only limonene and Eßf could be detected in all the Ri, Oe, and Wt lines, whereas other six volatiles were only found in the blend of volatiles from Oe lines. Moreover, the amount of constitutive limonene and Eßf in the Ri lines was significantly lower than in Wt lines, while the amounts of these two volatiles in the Oe line were obviously higher than in control rice. Our data suggested that the constitutive emissions of Eßf and limonene regulated by the constitutive expression of tps46 may play a crucial role in rice defense against R. padi. Consequently, tps46 could be a potential target gene to be employed for improving the resistance of plants to aphids.

Dynamic transcriptome analysis and volatile profiling of Gossypium hirsutum in response to the cotton bollworm Helicoverpa armigera.

In response to insect herbivory, plants emit elevated levels of volatile organic compounds for direct and indirect resistance. However, little is known about the molecular and genomic basis of defense response that insect herbivory trigger in cotton plants and how defense mechanisms are orchestrated in the context of other biological processes. Here we monitored the transcriptome changes and volatile characteristics of cotton plants in response to cotton bollworm (CBW; Helicoverpa armigera) larvae infestation. Analysis of samples revealed that 1,969 transcripts were differentially expressed (log2|Ratio| ≥ 2; q ≤ 0.05) after CBW infestation. Cluster analysis identified several distinct temporal patterns of transcriptome changes. Among CBW-induced genes, those associated with indirect defense and jasmonic acid pathway were clearly over-represented, indicating that these genes play important roles in CBW-induced defenses. The gas chromatography-mass spectrometry (GC-MS) analyses revealed that CBW infestation could induce cotton plants to release volatile compounds comprised lipoxygenase-derived green leaf volatiles and a number of terpenoid volatiles. Responding to CBW larvae infestation, cotton plants undergo drastic reprogramming of the transcriptome and the volatile profile. The present results increase our knowledge about insect herbivory-induced metabolic and biochemical processes in plants, which may help improve future studies on genes governing processes.

Preparation of acetylsalicylic acid-acylated chitosan as a novel polymeric drug for drug controlled release.

The acetylsalicylic acid-acylated chitosan (ASACTS) with high degree of substitution (DS) was successfully synthesized, and characterized with FTIR, (1)H NMR and elemental analysis methods. The optimum synthesis conditions were obtained which gave the highest DS (about 60%) for ASACTS. Its drug release experiments were carried out in simulated gastric and intestine fluids. The results show that the drugs in the form of acetylsalicylic acid (ASA) and salicylic acid (SA) were released in a controlled manner from ASACTS only in simulated gastric fluid. The release profile can be best fitted with logistic and Weibull model. The research results reveal that ASACTS can be a potential polymeric drug for the controlled release of ASA and SA in the targeted gastric environment.