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Polynucleotide phosphorylase is a highly conserved protein found in bacteria and fungi that can regulate the transcription of related enzymes involved in amino acid metabolism, organic acid metabolism, and cell biosynthesis. We studied the effect of polynucleotide phosphorylase on Saccharopolyspora pogona (S. pogona) growth and the synthesis of secondary metabolites. First, we generated the overexpression vector pOJ260-PermE-pnp via overlap extension PCR. The vector pOJ260-PermE-pnp was then introduced into S. pogona by conjugal transfer, thereby generating the recombination strain S. pogona-Pnp. Results showed that engineering strains possessed higher biomass than those of the wild-type strains. Moreover, the ability of these strains to produce spores on solid medium was stronger than that of the wild-type strains. HPLC results revealed that the butenyl-spinosyn yield in S. pogona-Pnp increased by 1.92-fold compared with that of S. pogona alone. These findings revealed that overexpression of polynucleotide phosphorylase effectively promoted butenyl-spinosyn biosynthesis in S. pogona. This result may be extended to other Streptomyces for strain improvement. [ABSTRACT FROM AUTHOR]

Olfactory bioassays were performed to investigate the specific odors utilized as host location cues by the beetle parasitoid, Scleroderma guani (Hymenoptera: Bethylidae), a primary biological control agent against Monochamus alternates (Coleoptera: Cerambycidae), the most important vector beetle of the pinewood nematode, Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae), the causal agent for pine wilt disease. Female parasitoids were tested with volatiles and extracts derived from their host beetle. Behavioral assays (Y-olfactometer bioassay and circle arena) demonstrated the response of female parasitoids to odors from host plants damaged by beetle larvae and from their excreta. When available contact cues were additionally provided, the parasitoids showed particularly strong preferences for samples of fresh brown frass of larval beetles. To confirm the electroantennograms (EAG) activity of identified compounds, analyses were repeated with a synthetic blend composed predominantly of compounds in the crude extracts that had revealed apparent electrophysiological activity. Antennal responses to four monoterpenes and three oxygenated monoterpenes were among the strongest, which indicated their potential for use in development of semichemial-based management of the beetle. [ABSTRACT FROM AUTHOR]

Much attention has been paid to the question of the relative importance of female behaviour versus larval feeding capacities in determining the host range of herbivorous insects. Host-use trade-offs displayed by generalist and specialist sister species of the genus Helicoverpa were evaluated to examine the relationship between maternal choice and offspring performance. The prediction of optimal oviposition theory, that females will choose to lay eggs on plants on which their offspring perform best as larvae, was tested by measuring oviposition preference and larval performance of Helicoverpa armigera and H. assulta on tobacco, sunflower, and hot pepper. These two measures were more highly correlated in the specialist H. assulta. Both species exhibited the same oviposition preference ranking: tobacco > sunflower > hot pepper. H. armigera larvae preferred sunflower, followed by tobacco and hot pepper; while H. assulta larvae preferred tobacco to sunflower and hot pepper, consistent with their mothers' oviposition preference. Duration of the total period from egg to adult emergence for each species was significantly shorter on the host plant preferred by the larvae. H. assulta had shorter larval duration and higher relative growth rate than H. armigera on tobacco and hot pepper, and vice versa for sunflower, indicating species differences in host utilization. Thus, while only the specialist H. assulta displayed the predicted optimal oviposition pattern, females of both species show the least preference for the plant on which their offspring perform worst. Selection for optimal oviposition may be stronger on the specialist, which has fewer choices and lower lifetime fecundity than the generalist. [ABSTRACT FROM AUTHOR]