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Leptographium qinlingensis is one of the major fungal associates of the Chinese white pine beetle (Dendroctonus armandi) and is an active participant in the large-scale death of Pinus armandi. Beetles and associated fungi have evolved efficient systems for overcoming the toxicity of host defense chemicals, which consist of a multitude of monoterpenes and diterpenes. As fungal cytochromes (CYPs) can detoxify and degrade various xenobiotic compounds, we identified 11 CYPs from L. qinlingensis to analyze their potential function in detoxifying or degrading host chemical defense. These 11 CYPs of L. qinlingensis belong to 6 clans and cluster into 3 clades, clade 2, clade 8 and clade 10, based on their phylogenetic relationships. Moreover, we also analyzed the transcript levels of CYPs following treatment with terpenes or expression in mycelia grown on terpenoids as a carbon source. The results in this paper showed that several CYPs were upregulated after treatment with terpenes or growth on terpenoids as the only carbon source. Our research provides some insight into the function of CYPs from bark beetle symbiotic fungi in the detoxification of pine defense compounds or their relationships with the utilization of terpenoids. [ABSTRACT FROM AUTHOR]

Ascorbate in leaf apoplast (ASCapo) reacts with ozone (O3) and thereby reduces O3 flux reaching plasmalemma (Fpl). Some studies have shown significant protection of cells from O3 by ASCapo, while others have questioned its efficacy. Hypothesizing that the protection by ASCapo depends on other variables, we quantified determinants of O3 detoxification with a model of O3 transport and reaction in apoplast. The model determines ascorbic acid concentration in apoplast (AAapo) using measured values of O3 concentration (co), leaf tissue ascorbic acid concentration (AAleaf), cell wall thickness (L3), apoplastic pH (pHapo), and stomatal conductance (Gsw). We compared the measured and model‐estimated AAapo in leaves of peach (Prunus persica) grown in open‐top chambers under non‐filtered air (NF) and elevated (EO3: NF + 80 ppb) O3 concentrations. The estimated AAapo in individual leaves agreed well with the measured values (R2 =.91). Analyses of the simulation results yielded the following findings: (a) The efficacy of O3 reduction with ASCapo as quantified by fractional reduction (ϕ3) of O3 flux at the surface of plasmalemma (Fpl) was lowered from 70% in NF to 40% in EO3 due to the reduction of L3. The EO3 reduced AAapo, but the lower Gsw and L3 in EO3 increased AAapo resulting in no significant change in AAapo due to EO3. ϕ3 can be calculated with measured values of AAapo and L3, and Fpl can be estimated with the measurement‐based ϕ3. (b) When c0 is increased, Fpl increased curvilinearly with the increase of Fst: nominal O3 flux via stomatal diffusion, exhibiting apparent threshold on Fst. The deviation of Fpl from Fst became greater when L3, pHapo, and AAleaf were increased. The quantification of ϕ3 and Fpl using leaf traits shall facilitate the understanding of the mechanisms of differential plant sensitivity to O3 and improve quantification of the O3 impacts on plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bark beetles rely on detoxifying enzymes to resist the defensive terpenoids of their host trees. Research on carboxylesterases (CarEs) has focused on their multiple functions in the metabolic detoxification of pesticides and plant allelochemicals, drug resistance, and juvenile hormone and pheromone degradation. RESULT: We identified eight new CarE genes in the Chinese white pine beetle (Dendroctonus armandi) and carried out bioinformatics analysis on the deduced full‐length amino acid sequences. Differential transcript levels of CarE genes were observed between sexes; within these levels, significant differences were found among the different development stages, and between insects fed on the phloem of Pinus armandi and exposed to five stimuli [(−)‐α‐pinene, (−)‐β‐pinene, (+)‐3‐carene, limonene and turpentine] at 8 and 24 h. CONCLUSION: Transcription levels of CarE genes suggest some relationship with the detoxification of terpenoids released by host trees. The functions of bark beetle esterase are mainly in hydrolyzing the host chemical defense and degrading odorant molecules during host selection and colonization. © 2018 Society of Chemical Industry The functions of bark beetle esterase are mainly to hydrolyze the host chemical defense and degrade odorant molecules during host selection and colonization. [ABSTRACT FROM AUTHOR]

Abstract Apoplastic ascorbate (ASC apo) is an important contributor to the detoxification of ozone (O 3). The objective of the study is to explore whether ASC apo is stimulated by elevated O 3 concentrations. The detoxification of O 3 by ASC apo was quantified in tobacco (Nicotiana L), soybean (Glycine max (L.) Merr.) and poplar (Populus L), which were exposed to charcoal-filtered air (CF) and elevated O 3 treatments (E-O 3). ASC apo in the three species were significantly increased by E-O 3 compared with the values in the filtered treatment. For all three species, E-O 3 significantly increased the malondialdehyde (MDA) content and decreased light-saturated rate of photosynthesis (A sat), suggesting that high O 3 has induced injury/damage to plants. E-O 3 significantly increased redox state in the apoplast (redox state apo) for all species, whereas no effect on the apoplastic dehydroascorbate (DHA apo) was observed. In leaf tissues, E-O 3 significantly enhanced reduced-ascorbate (ASC) and total ascorbate (ASC+DHA) in soybean and poplar, but significantly reduced these in tobacco, indicating different antioxidative capacity to the high O 3 levels among the three species. Total antioxidant capacity in the apoplast (TAC apo) was significantly increased by E-O 3 in tobacco and poplar, but leaf tissue TAC was significantly enhanced only in tobacco. Leaf tissue superoxide anion (O 2 •-) in poplar and hydrogen peroxide (H 2 O 2) in tobacco and soybean were significantly increased by E-O 3. The diurnal variation of ASC apo , with maximum values occurring in the late morning and lower values experienced in the afternoon, appeared to play an important role in the harmful effects of O 3 on tobacco, soybean and poplar. Graphical abstract Image 1 Highlights • Apoplastic antioxidant was investigated in three species under two O 3 treatments. • Apoplastic reduced-ascorbate is induced by high instantaneous O 3 concentrations. • Apoplastic reduced-ascorbate displays a diurnal variation. • Increase of apoplastic ascorbate induced by O 3 is insufficient to protect plants from O 3. Apoplastic ascorbate was induced by high ozone. [ABSTRACT FROM AUTHOR]

BACKGROUND Bark beetles rely on their detoxifying enzymes to resist the defensive terpenoids of host trees. Glutathione S-transferases ( GSTs) conjugate xenobiotic compounds with a glutathione moiety ( GSH) and often work in tandem with cytochromes P450 or other enzymes that aid in the detoxification, sequestration or excretion of toxic compounds. RESULT We identified nine new GST genes in the Chinese white pine beetle ( Dendroctonus armandi) and carried out a bioinformatics analysis on the deduced full-length amino acid sequences. These genes belong to four different classes (epsilon, sigma, omega and theta). Differential transcript levels of each class of GST genes were observed between sexes, and, within these levels, significant differences were found among the different adult substages that were fed phloem of Pinus armandi and exposed to six stimuli [(±)- α-pinene, (−)- α-pinene, (−)- β-pinene, (+)-3-carene, (±)-limonene and turpentine] at 8 and 24 h. CONCLUSION The increased transcription levels of GST genes suggested that they have some relationship with the detoxification of terpenoids that are released by host trees. The mediating oxidative stress that is caused by monoterpene might be the main role of the bark beetle GSTs. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Bark beetles oxidize the defensive allelochemicals from their host trees to both detoxify and convert these materials into components of their pheromone system. The ability of this insect to adapt to its chemical environment might be explained by the action of major detoxification enzymes such as cytochrome P450s (or CYPs). Sixty-four sequences coding for P450s were identified, and most of the transcripts were found to be expressed in the larvae, pupae and adults of Dendroctonus armandi . To gain information on how these genes help D. armandi overcome the host defense, differential transcript levels of the CYP genes were observed between sexes and within the sexes. Significant differences were observed among developmental stages, in feeding on the phloem of Pinus armandi and in exposure to stimuli ((±)-α-pinene, (S)-(−)-α-pinene, (S)-(−)-β-pinene, (+)-3-carene, (±)-limonene and turpentine oil) for 8 h. We investigated the effect of sex and generations on the survivorship of individual D. armandi that were exposed to host volatiles at concentrations comparable to constitutive and induced levels of defense using fumigant exposure to understand the ability of the beetles to tolerate host defensive chemicals. The differential transcript accumulation patterns of CYP genes of these bark beetle provided insight into the ecological interactions of D. armandi with its host pine. [ABSTRACT FROM AUTHOR]