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Both insects and pathogens release effectors that are transferred into plant cells and weaken the host defense or immune response. While the imports of some bacterial and fungal effectors into plants have been reported, how caterpillar effectors enter plant cells remains a mystery. Here, using live cell imaging and real-time protein tracking, we show that HARP1, an effector from oral secretions of cotton bollworm (Helicoverpa armigera) which is previously reported to interfere with defense hormone jasmonate (JA) signaling output in host plants, enters plant cells via protein-mediated endocytosis. The interactions of HARP1 with vesicle trafficking components including CTL1, PATL2 and TET8 are essential for its entry. Notably, JA restricts HARP1 import by inhibiting endocytosis and HARP1 loading on endosomes. Taken together, the effector and JA set up a defense and counter-defense loop in the arm race between plants and insects. Our study unveils a new paradigm for the plant-insect interaction.

Caterpillar oral secretion (OS) contains active molecules that modulate plant defense signaling. We isolated an effector-like protein (Highly Accumulated Secretory Protein 1, HAS1) from cotton bollworm (Helicoverpa armigera) that is the most highly accumulated secretory protein of the nondigestive components in OS and belongs to venom R-like protein. Elimination of HAS1 by plant-mediated RNA interference reduced the suppression of OS on the defense response in plants. Plants expressing HAS1 are more susceptible to insect herbivory accompanied by the reduced expressions of multiple defense genes. HAS1 binds to the basic helix-loop-helix (bHLH) transcription factors, including GoPGF involved in pigmented gland formation and defense compounds biosynthesis in cotton and MYC3/MYC4 the main regulators in jasmonate (JA) signaling in Arabidopsis. The binding activity is required for HAS1 to inhibit the activation of bHLHs on plant defense gene expressions. Together with our previous study that another venom R-like protein HARP1 in cotton bollworm OS blocks JA signaling by interacting with JASMONATE-ZIM-domain repressors, we conclude that the venom R-like proteins in OS interfere with plant defense in a dual suppression manner. Considering the venom proteins in parasitic wasp assault the immune system of its host animal, our investigation reveals their conserved function in carnivorous and herbivorous insects.

Age and wounding are two major determinants for regeneration. In plants, the root regeneration is triggered by wound-induced auxin biosynthesis. As plants age, the root regenerative capacity gradually decreases. How wounding leads to the auxin burst and how age and wound signals collaboratively regulate root regenerative capacity are poorly understood. Here, we show that the increased levels of three closely-related miR156-targeted Arabidopsis (Arabidopsis thaliana) SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors, SPL2, SPL10, and SPL11, suppress root regeneration with age by inhibiting wound-induced auxin biosynthesis. Mechanistically, we find that a subset of APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factors including ABSCISIC ACID REPRESSOR1 and ERF109 is rapidly induced by wounding and serves as a proxy for wound signal to induce auxin biosynthesis. In older plants, SPL2/10/11 directly bind to the promoters of AP2/ERFs and attenuates their induction, thereby dampening auxin accumulation at the wound. Our results thus identify AP2/ERFs as a hub for integration of age and wound signal for root regeneration.

As sessile and autotrophic organisms, plants have evolved sophisticated pathways to produce a rich array of specialized metabolites, many of which are biologically active and function as defense substances in protecting plants from herbivores and pathogens. Upon stimuli, these structurally diverse small molecules may be synthesized or constitutively accumulated. Jasmonate acids (JAs) are the major defense phytohormone involved in transducing external signals (such as wounding) to activate defense reactions, including, in particular, the reprogramming of metabolic pathways that initiate and enhance the production of defense compounds against insect herbivores and pathogens. In this review, we summarize the progress of recent research on the control of specialized metabolic pathways in plants by JA signaling, with an emphasis on the molecular regulation of terpene and alkaloid biosynthesis. We also discuss the interplay between JA signaling and various signaling pathways during plant defense responses. These studies provide valuable data for breeding insect-proof crops and pave the way to engineering the production of valuable metabolites in future.

Significance Plants recognize insect-derived molecules and make the accurate defense response during herbivory. However, insects release effectors that disturb host plant defense responses for fitness. Effectors are crucial components in biotic interactions. We identified a caterpillar-derived effector (HARP1) from oral secretion of cotton bollworm, a devastating agricultural pest. HARP1 is released from larvae to plant leaves during feeding and is able to migrate from wounding site into plant cells automatically. HARP1 interacts with JASMONATE-ZIM-domain (JAZ) proteins, the suppressor of Jasmonate (JA) pathway, and blocks signaling transduction by preventing JAZ degradation. HARP1-like proteins are widely distributed and have conserved function in noctuids, and they may contribute to insect adaptation to host plants during coevolution., Insects have evolved effectors to conquer plant defense. Most known insect effectors are isolated from sucking insects, and examples from chewing insects are limited. Moreover, the targets of insect effectors in host plants remain unknown. Here, we address a chewing insect effector and its working mechanism. Cotton bollworm (Helicoverpa armigera) is a lepidopteran insect widely existing in nature and severely affecting crop productivity. We isolated an effector named HARP1 from H. armigera oral secretion (OS). HARP1 was released from larvae to plant leaves during feeding and entered into the plant cells through wounding sites. Expression of HARP1 in Arabidopsis mitigated the global expression of wounding and jasmonate (JA) responsive genes and rendered the plants more susceptible to insect feeding. HARP1 directly interacted with JASMONATE-ZIM-domain (JAZ) repressors to prevent the COI1-mediated JAZ degradation, thus blocking JA signaling transduction. HARP1-like proteins have conserved function as effectors in noctuidae, and these types of effectors might contribute to insect adaptation to host plants during coevolution.

The green mirid bug (Apolygus lucorum) and the cotton bollworm (Helicoverpa armigera) are both preferred to live on cotton but cause different symptoms, suggesting specialized responses of cotton to the two insects. In this study, we investigated differential molecular mechanisms underlying cotton plant defenses against A. lucorum and H. armigera via transcriptomic analyses. At the transcription level, jasmonate (JA) signaling was dominated in defense against H. armigera whereas salicylic acid (SA) signaling was more significant in defense against A. lucorum. A set of pathogenesis-related (PR) genes and protease inhibitor genes were differentially induced by the two insects. Insect infestations also had an impact on alternative splicing (AS), which was altered more significantly by the H. armigera than A. lucorum. Interestingly, most differential AS (DAS) genes had no obvious change at the transcription level. GO analysis revealed that biological process termed “RNA splicing” and “cellular response to abiotic stimulus” were enriched only in DAS genes from the H. armigera infested samples. Furthermore, insect infestations induced the retained intron of GhJAZs transcripts, which produced a truncated protein lacking the intact Jas motif. Taken together, our data demonstrate that the specialized cotton response to different insects is regulated by gene transcription and AS as well.

Summary Cotton cultivars have evolved to produce extensive, long, seed‐born fibers important for the textile industry, but we know little about the molecular mechanism underlying spinnable fiber formation. Here, we report how PACLOBUTRAZOL RESISTANCE 1 (PRE1) in cotton, which encodes a basic helix‐loop‐helix (bHLH) transcription factor, is a target gene of spinnable fiber evolution.Differential expression of homoeologous genes in polyploids is thought to be important to plant adaptation and novel phenotypes. PRE1 expression is specific to cotton fiber cells, upregulated during their rapid elongation stage and A‐homoeologous biased in allotetraploid cultivars. Transgenic studies demonstrated that PRE1 is a positive regulator of fiber elongation.We determined that the natural variation of the canonical TATA‐box, a regulatory element commonly found in many eukaryotic core promoters, is necessary for subgenome‐biased PRE1 expression, representing a mechanism underlying the selection of homoeologous genes.Thus, variations in the promoter of the cell elongation regulator gene PRE1 have contributed to spinnable fiber formation in cotton. Overexpression of GhPRE1 in transgenic cotton yields longer fibers with improved quality parameters, indicating that this bHLH gene is useful for improving cotton fiber quality.

The green mirid bug Apolygus lucorum is an agricultural pest that is known to cause damage to more than 150 plant species. Here, we report the transcriptomes of A. lucorum at three different developmental stages (the second and fifth instar nymphs and adults). A total of 98,236 unigenes with an average length of 1,335 nt was obtained, of which 50,640 were annotated, including those encoding digestive enzymes and cytochrome P450s. Comparisons with cotton bollworm and cotton aphid transcriptomes revealed distinct features of A. lucorum as a mesophyll feeder. The gene expression dynamics varied during development from young nymphs to adults. The high-quality transcriptome data and the gene expression dynamics reported here provide valuable data for a more comprehensive understanding of the physiology and development of mirid bugs, and for mining targets for their control.

Summary Plant engineered to express double-stranded RNA (dsRNA) can target the herbivorous insect gene for silencing. Although mounting evidence has emerged to support feasibility of this new pest control technology, field application is slow largely due to lack of potent targets. Here, we show that suppression of the gene encoding NDUFV2, a subunit of mitochondrial complex I that catalyses NADH dehydrogenation in respiratory chain, was highly lethal to insects. Feeding cotton bollworm (Helicoverpa armigera) larvae with transgenic cotton tissues expressing NDUFV2 dsRNA led to mortality up to 80% within 5 days, and almost no larvae survived after 7 days of feeding, due to the altered mitochondrial structure and activity. Transcriptome comparisons showed a drastic repression of dopa decarboxylase genes. Reciprocal assays with Asian corn borer (Ostrinia furnacalis), another lepidopteran species, revealed the sequence-specific effect of NDUFV2 suppression. Furthermore, the hemipteran lugus Apolygus lucorum was also liable to NDUFV2 repression. These data demonstrate that the mitochondrial complex I is a promising target with both sequence specificity and wide applicability for the development of new-generation insect-proof crops.

Gossypol and related sesquiterpene aldehydes in cotton function as defense compounds but are antinutritional in cottonseed products. By transcriptome comparison and coexpression analyses, we identified 146 candidates linked to gossypol biosynthesis. Analysis of metabolites accumulated in plants subjected to virus-induced gene silencing (VIGS) led to the identification of four enzymes and their supposed substrates. In vitro enzymatic assay and reconstitution in tobacco leaves elucidated a series of oxidative reactions of the gossypol biosynthesis pathway. The four functionally characterized enzymes, together with (+)-δ-cadinene synthase and the P450 involved in 7-hydroxy-(+)-δ-cadinene formation, convert farnesyl diphosphate (FPP) to hemigossypol, with two gaps left that each involves aromatization. Of six intermediates identified from the VIGS-treated leaves, 8-hydroxy-7-keto-δ-cadinene exerted a deleterious effect in dampening plant disease resistance if accumulated. Notably, CYP71BE79, the enzyme responsible for converting this phytotoxic intermediate, exhibited the highest catalytic activity among the five enzymes of the pathway assayed. In addition, despite their dispersed distribution in the cotton genome, all of the enzyme genes identified show a tight correlation of expression. Our data suggest that the enzymatic steps in the gossypol pathway are highly coordinated to ensure efficient substrate conversion.

Figures S1-S4; Tables S1-S3

Various collectors and combinations of them were used for experimental study on flotation of oxide copper ore in Huidong and the results showed that isoamyl xanthate would be a proper collector agent. When using it at 550g/t, the rough concentrate grade was 3.97%, and the recovery rate reached its highest value of 83.05%.

Methods used for mineral processing-metallurgy combined processes of copper oxide ore were reviewed and the research directions of copper oxide ore were pointed out.

The extractant M5640 that extracted and stripped copper in the ammonia leach solution of copper oxidized ores solution of were mainly studied for the experimentation examined the M5640 concentration, phase ratio, extraction time, and liquid pH. Laboratory Investigations indicated that M5640 is really an efficient copper extractant with a maximum extraction of as high as 99.64% under the conditions of 6.48g/L Cu in leach solution, the extraction agent concentration is 10%, phase ratio is 1:1, extraction time is 2 min and liquid pH was 9.58. The stripping can be conducted with the barren electrolyte as a stripping agent in which the sulfuric acid concentration remains about 150g/L, and a stripping rate of 99.80% is obtained.

Ammonia leaching research is carried out on a certain oxidised copper ores. The effects of oxidized copper ores which came from Yunnan Province were studied in laboratory in order to find out the optimum leaching conditions under normal temperature and pressure. The ores belonged to typical high binding rate minerals. The optimum conditions obtained were as follows: granding fineness about 90% -0.074mm, ammonia concentration 2 mol/l, ammonium fluoride concentration 1.5mol/l , leaching time 2h, and liquid-solid ratio 3:1.The leaching rate of this ore could reach 86%.

Flotation experimental research is carried out on a certain oxidised copper ores in Huidong, Sichuan province. The ores belongs to the typical oxidised ores. For the characteristics of the mine and the scene of the test requirements, five different flowsheets were test. Under the proper process conditions, the good technical indexes were obtained in all flowsheets. But the the fourth flotation flowsheet was choosed. The principle process of two roughing, one scavenging and two cleaning were used in flotation process. Both the scavenging foam and tailing of first cleaning are returned to the first roughing work and tailing of second cleaning is returned to first cleaning work in closed circuit.

For refractory oxidised copper ores of Huidong Sichuan province, studing the different depressants on the influence of oxidised copper ores flotation behavior. The results showed that: the depressanting effect of the combination of sodium hexametaphosphate primarily is better. When the dosage of the combination of sodium hexametaphosphate and sodium humate reagent is 300 g/t, ratio is 2:1,the recovery of copper concentrate is 83.31and the grade is 19.01 in the closed circuit experiment.

To improve the recovery of copper from refractory copper oxidized ore by sulfidization-flotation process. The result determined the optimal flotation process parameters of refractory copper oxidized ore, and the better quota selecting separately obtained by a large number of research. The copper concentrate grade reaches 10.85%, the recovery reaches 57.41%.

Flotation experimental research is carried out on a certain sulphide copper ore of Sifangjing in Huidong, Sichuan province. The ore exist in the deeper part of ore deposit. Because of the deep burried, the oxidation rate is relatively low. The ore belongs to the typical sulfide ore. For the characteristics of the mine and the scene of the test requirements, the use of direct flotation process has achieved a successful recovery of copper. In the cleaning operation ,Strengthen copper sulfur separation to obtain qualified copper concentrate. Under the proper process conditions ,the good technical indexes were obtained.

Floatation experimental research is carried out on a certain complicated ore containing mixed sulphides in Yannan province. For the characteristics of the mine and the scene of the test requirements, the use of mixed flotation-separation process has achieved a successful recovery of useful elements. Combination inhibitors can effectively achieve the separation of copper and sulfur .Under the proper process conditions ,the good technical indexes were obtained.

In this study, the dissolution effect of zinc oxide ore was investigated using sulfamic acid solution as leaching agent. The effects of temperature, concentration of sulfamic acid, average particle size and stirring speed on the dissolution of zinc oxide ore were investigated. The dissolution rate increased with increasing solution temperature, concentration, and stirring speed as well as with decreasing average particle size. Sulfamic acid solution can therefore be used as an effective leaching agent for zinc extraction from zinc oxide ore.

Plant secondary metabolites and their biosynthesis have attracted great interest, but investigations of the activities of hidden intermediates remain rare. Gossypol and related sesquiterpenes are the major phytoalexins in cotton. Among the six biosynthetic intermediates recently identified, 8-hydroxy-7-keto-δ-cadinene (C234) crippled the plant disease resistance when accumulated upon gene silencing. C234 harbours an α,β-unsaturated carbonyl thus is a reactive electrophile species. Here, we show that C234 application also dampened the Arabidopsis resistance against the bacterial pathogen Pseudomonas syringae pv. maculicola ( Psm ). We treated Arabidopsis with C234, Psm and ( Psm +C234), and analysed the leaf transcriptomes. While C234 alone exerted a mild effect, it greatly stimulated an over-response to the pathogen. Of the 7335 genes affected in the ( Psm +C234)-treated leaves, 3476 were unresponsive without the chemical, in which such functional categories as ‘nucleotides transport’, ‘vesicle transport’, ‘MAP kinases’, ‘G-proteins’, ‘protein assembly and cofactor ligation’ and ‘light reaction’ were enriched, suggesting that C234 disturbed certain physiological processes and the protein complex assembly, leading to distorted defence response and decreased disease resistance. As C234 is efficiently metabolized by CYP71BE79, plants of cotton lineage have evolved a highly active enzyme to prevent the phytotoxic intermediate accumulation during gossypol pathway evolution. This article is part of the theme issue ‘Biotic signalling sheds light on smart pest management’.

Leaching test on the Oxidized Zinc Ore coming from Yunnan Province is studied in the H2SO4 system;Systematic studies are made to show the effects of various factors on the leaching rate of zinc. The optimum conditions for leaching is finally confirmed, namely the grinding size is 75% of-0.074mm, concentration of sulfuric acid 15%, temperature 60°C, solid to liquid ratio 3:1, and leaching time 2.5h. Ultimately, the leaching rate of Zn could reach more than 59%.

This paper use the copper content of copper-rich solution is 49.43g/L for electrolyte, and it effecting factors of the quality of electric copper electrodeposition are studied. The results show that under the these conditions of the electrodeposition current density is 180A/m2, and time of electrodeposition is 1.5h, concentration of NH4+ in electrolyte is less than 2g/L, thiourea is 40 g/t and Henkel glue is 40 g/t, the cathode copper which have less impurity content and Cu+Ag≥99.95% could be obtained.

Oral ingestion of plant-expressed double stranded RNA (dsRNA) triggers target gene suppression in insect. An important step of this process is the transmission of dsRNA from plant to midgut cells. Insect peritrophic matrix (PM) presents a barrier that prevents large molecules from entering midgut cells. Here, we show that uptake of plant cysteine proteases, such as GhCP1 from cotton (Gossypium hirsutum) and AtCP2 from Arabidopsis, by cotton bollworm (Helicoverpa armigera) larvae resulted in attenuating the PM. When GhCP1 or AtCP2 pre-fed larvae were transferred to gossypol-containing diet, the bollworm accumulated higher content of gossypol in midgut. Larvae previously ingested GhCP1 or AtCP2 were more susceptible to infection by Dendrolimus punctatus cytoplasmic polyhedrosis virus (DpCPV), a dsRNA virus. Furthermore, the pre-fed larvae exhibited enhanced RNAi effects after ingestion of the dsRNA-expressing plant. The bollworm P450 gene CYP6AE14 is involved in the larval tolerance to gossypol; cotton plants producing dsRNA of CYP6AE14 (dsCYP6AE14) were more resistant to bollworm feeding (Mao et al. in Transgenic Res 20:665–673, 2011). We found that cotton plants harboring both 35S:dsCYP6AE14 and 35S:GhCP1 were better protected from bollworm than either of the single-transgene lines. Our results demonstrate that plant cysteine proteases, which have the activity of increasing PM permeability, can be used to improve the plant-mediated RNAi against herbivorous insects. Electronic supplementary material The online version of this article (doi:10.1007/s11103-013-0030-7) contains supplementary material, which is available to authorized users.

The extractant LIX84-I that extracted and stripped copper in the ammonia leach solution of copper oxidized ores solution of were mainly studied for the experimentation examined the influence of the LIX84-I concentration, the extraction time, the phase ratio, the pH , the stripping sulfuric acid concentration and the stripping time. Laboratory Investigations indicated that LIX84-I is really an efficient copper extractant with a maximum extraction of as high as 99.91% under the conditions of 5.23g/L Cu in leach solution, LIX84-I concentration 7%, 3 min mixtures, phase ratio 1/1and pH﹥4.5. The stripping can be conducted with the barren electrolyte as a stripping agent in which the sulfuric acid concentration remains about 150g/L, and a stripping rate of 99.92% is obtained.

This paper introduces the survey of bauxite resources in China, analyses the basal principle of selective dissociation, then details dissociation process flow and selective grinding, finally prospects the future development of bauxite selective dissociation.

Huize oxidized lead-zinc ore contains 1.53% Pb, 16.67% Zn, and the oxidation rate of lead reaches up to 95.07%, zinc is 85.27%, belongs to high-zinc but low-lead oxidized lead-zinc ore. According to the characters of ore, the technology that lead prior to zinc and desliming in oxidized zinc flotation has been adopted, as well as combined modifiers, ideal performance that grade and recovery of lead concentrate reaching to 51.61% and 62.54% respectively, and zinc concentrate reaching to 38.90% and 70.22% respectively has been obtained.

The experiments of refractory copper oxide ore which comes from Tangdan of Yunnan Province were studied in laboratory using bulk flotation process and a new process that Ammonia leaching-Extraction-Electrode position-Residue flotation under normal temperature and pressure respectively. The results show that new process, compared with bulk flotation, had an effect to add 10.8 percent points to recovery. And then it is confirmed by industry experiment. So it is successfully applied to industry production and technology indicators were improved dramatically.

Plant reproductive organs are vulnerable to heat, but regulation of heat-shock responses in inflorescence is largely uncharacterized. Here, we report that two of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcriptional factors in Arabidopsis, SPL1 and SPL12, act redundantly in thermotolerance at the reproductive stage. The spl1-1 spl12-1 inflorescences displayed hypersensitivity to heat stress, whereas overexpression of SPL1 or SPL12 enhanced the thermotolerance in both Arabidopsis and tobacco. RNA sequencing revealed 1939 upregulated and 1479 downregulated genes in wild-type inflorescence upon heat stress, among which one-quarter (1,040) was misregulated in spl1-1 spl12-1, indicating that SPL1 and SPL12 contribute greatly to the heat-triggered transcriptional reprogramming in inflorescence. Notably, heat stress induced a large number of abscisic acid (ABA) responsive genes, of which ∼39% were disturbed in heat induction in spl1-1 spl12-1 inflorescence. Preapplication of ABA and overexpression of SPL1 restored the inflorescence thermotolerance in spl1-1 spl12-1 and in the ABA biosynthesis mutant aba2-1, but not in the pyl sextuple mutant defective in ABA receptors PYR1/PYL1/PYL2/PYL4/PYL5/PYL8. Thus, inflorescence thermotolerance conferred by SPL1 and SPL2 involves PYL-mediated ABA signaling. The molecular network consisting of SPL1 and SPL12 illustrated here shed new light on the mechanisms of plant thermotolerance at the reproductive stage.

Plant secondary metabolites play critical roles in plant-environment interactions. They are synthesized in different organs or tissues at particular developmental stages, and in response to various environmental stimuli, both biotic and abiotic. Accordingly, corresponding genes are regulated at the transcriptional level by multiple transcription factors. Several families of transcription factors have been identified to participate in controlling the biosynthesis and accumulation of secondary metabolites. These regulators integrate internal (often developmental) and external signals, bind to corresponding cis-elements--which are often in the promoter regions--to activate or repress the expression of enzyme-coding genes, and some of them interact with other transcription factors to form a complex. In this review, we summarize recent research in these areas, with an emphasis on newly-identified transcription factors and their functions in metabolism regulation.

Flotation of Jinping refractory copper oxide ore activated by a combined reagent of amine and ammonium has been fully studied in present study. The results show that the combined reagent (i.e., ethylenediamine phosphate and ammonium bicarbonate) has a remarkable effect on flotation performance, which can not only effectively activate the refractory copper oxide mineral, but also depress the slime of bauxite and some other impurities, such as cadmium, magnesium and silicon, etc. At last, a copper recovery of 76% with a concentrate grade of 21.65% was achieved from the ore.

Cotton plants accumulate phytotoxins, including gossypol and related sesquiterpene aldehydes, to resist insect herbivores and pathogens. To counteract these defensive plant secondary metabolites, cotton bollworms (Helicoverpa armigera) elevate their production of detoxification enzymes, including cytochrome P450 monooxygenases (P450s). Besides their tolerance to phytotoxin, cotton bollworms have quickly developed resistance to deltamethrin, a widely used pyrethroid insecticide in cotton field. However, the relationship between host plant secondary metabolites and bollworm insecticide resistance is poorly understood. Here, we show that exogenously expressed CYP6AE14, a gossypol-inducible P450 of cotton bollworm, has epoxidation activity towards aldrin, an organochlorine insecticide, indicating that gossypol-induced P450s participate in insecticide metabolism. Gossypol-ingested cotton bollworm larvae showed higher midgut P450 enzyme activities and exhibited enhanced tolerance to deltamethrin. The midgut transcripts of bollworm larvae administrated with different phytochemicals and deltamethrin were then compared by microarray analysis, which showed that gossypol and deltamethrin induced the most similar P450 expression profiles. Gossypol-induced P450s exhibited high divergence and at least five of them (CYP321A1, CYP9A12, CYP9A14, CYP6AE11 and CYP6B7) contributed to cotton bollworm tolerance to deltamethrin. Knocking down one of them, CYP9A14, by plant-mediated RNA interference (RNAi) rendered the larvae more sensitive to the insecticide. These data demonstrate that generalist insects can take advantage of secondary metabolites from their major host plants to elaborate defence systems against other toxic chemicals, and impairing this defence pathway by RNAi holds a potential for reducing the required dosages of agrochemicals in pest control.

We identify a cytochrome P450 gene (CYP6AE14) from cotton bollworm (Helicoverpa armigera), which permits this herbivore to tolerate otherwise inhibitory concentrations of the cotton metabolite, gossypol. CYP6AE14 is highly expressed in the midgut and its expression correlates with larval growth when gossypol is included in the diet. When larvae are fed plant material expressing double-stranded RNA (dsRNA) specific to CYP6AE14, levels of this transcript in the midgut decrease and larval growth is retarded. Both effects are more dramatic in the presence of gossypol. As a glutathione-S-transferase gene (GST1) is silenced in GST1 dsRNA-expressing plants, feeding insects plant material expressing dsRNA may be a general strategy to trigger RNA interference and could find applications in entomological research and field control of insect pests.

Among plant secondary metabolites terpenoids are a structurally most diverse group; they function as phytoalex- ins in plant direct defense, or as signals in indirect defense responses which involves herbivores and their natural enemies. In recent years, more and more attention has been paid to the investigation of the ecological role of plant terpenoids. The biosynthesis pathways of monoterpenes, sesquiterpenes, and diterpenes include the synthesis of C5 precursor isopentenyl diphosphate (IPP) and its allylic isomer dimethylallyl diphosphate (DMAPP), the synthe- sis of the immediate diphosphate precursors, and the formation of the diverse terpenoids. Terpene synthases (TPSs) play a key role in volatile terpene synthesis. By expression of the TPS genes, significant achievements have been made on metabolic engineering to increase terpenoid production. This review mainly summarizes the recent research progress in elucidating the ecological role of terpenoids and characterization of the enzymes involved in the terpenoid biosynthesis. Spatial and temporal regulations of terpenoids metabolism are also discussed.

Of the two cultivated species of allopolyploid cotton, Gossypium barbadense produces extra-long fibers for the production of superior textiles. We sequenced its genome (AD)2 and performed a comparative analysis. We identified three bursts of retrotransposons from 20 million years ago (Mya) and a genome-wide uneven pseudogenization peak at 11–20 Mya, which likely contributed to genomic divergences. Among the 2,483 genes preferentially expressed in fiber, a cell elongation regulator, PRE1, is strikingly At biased and fiber specific, echoing the A-genome origin of spinnable fiber. The expansion of the PRE members implies a genetic factor that underlies fiber elongation. Mature cotton fiber consists of nearly pure cellulose. G. barbadense and G. hirsutum contain 29 and 30 cellulose synthase (CesA) genes, respectively; whereas most of these genes (>25) are expressed in fiber, genes for secondary cell wall biosynthesis exhibited a delayed and higher degree of up-regulation in G. barbadense compared with G. hirsutum, conferring an extended elongation stage and highly active secondary wall deposition during extra-long fiber development. The rapid diversification of sesquiterpene synthase genes in the gossypol pathway exemplifies the chemical diversity of lineage-specific secondary metabolites. The G. barbadense genome advances our understanding of allopolyploidy, which will help improve cotton fiber quality.

Immunity deteriorates with age in animals but comparatively little is known about the temporal regulation of plant resistance to herbivores. The phytohormone jasmonate (JA) is a key regulator of plant insect defense. Here, we show that the JA response decays progressively in Arabidopsis. We show that this decay is regulated by the miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) group of proteins, which can interact with JA ZIM-domain (JAZ) proteins, including JAZ3. As SPL9 levels gradually increase, JAZ3 accumulates and the JA response is attenuated. We provide evidence that this pathway contributes to insect resistance in young plants. Interestingly however, despite the decay in JA response, older plants are still comparatively more resistant to both the lepidopteran generalist Helicoverpa armigera and the specialist Plutella xylostella, along with increased accumulation of glucosinolates. We propose a model whereby constitutive accumulation of defense compounds plays a role in compensating for age-related JA-response attenuation during plant maturation., Immunity deteriorates with age in animals but less is known about how aging affects immunity in plants. Here, Mao et al. show that responsiveness to the major insect defense hormone JA declines as plants age, but insect resistance still increases as plants accumulate secondary metabolites such as glucosinolates.

The plant root cap mediates the direction of root tip growth and protects internal cells. Root cap cells are continuously produced from distal stem cells, and the phytohormone auxin provides position information for root distal organization. Here, we identify the Arabidopsis thaliana auxin response factors ARF10 and ARF16, targeted by microRNA160 (miR160), as the controller of root cap cell formation. The Pro35S:MIR160 plants, in which the expression of ARF10 and ARF16 is repressed, and the arf10-2 arf16-2 double mutants display the same root tip defect, with uncontrolled cell division and blocked cell differentiation in the root distal region and show a tumor-like root apex and loss of gravity-sensing. ARF10 and ARF16 play a role in restricting stem cell niche and promoting columella cell differentiation; although functionally redundant, the two ARFs are indispensable for root cap development, and the auxin signal cannot bypass them to initiate columella cell production. In root, auxin and miR160 regulate the expression of ARF10 and ARF16 genes independently, generating a pattern consistent with root cap development. We further demonstrate that miR160-uncoupled production of ARF16 exerts pleiotropic effects on plant phenotypes, and miR160 plays an essential role in regulating Arabidopsis development and growth.