Krishnan, Natraj

Abstract BACKGROUND The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has emerged as a major pest of cotton, Gossypium hirsutum L, in the mid‐southern USA. In the early 1990s L. lineolaris populations developed resistance to several classes of conventional insecticides, increasing the need for insecticides with alternative modes of action such as insect growth regulators (IGRs) for integrated pest management (IPM). The benzoylphenyl urea (BPU) class of IGRs acts by disrupting the growth and development of immature stages of insects, but little is known about its impact on adult stages. RESULTS The effect of novaluron (Diamond™ 0.83EC), a BPU with known chitin synthesis inhibitor activity, was investigated on adult females of L. lineolaris . Treatment of 1‐day‐old adults with 600 ppm of novaluron in the diet prevented oviposition, while treatment of older females had no impact on oviposition. Oral novaluron exposure of adults of all ages reduced the viability of eggs laid. Novaluron treatment caused ultrastructural changes in the ovaries of 1‐day‐old adults (48 h post exposure), distorting the follicular epithelial cell architecture of developing oocytes. Additionally, novaluron treatment decreased the chitin content in ovarian tissue. CONCLUSION Our results suggest that chitin or chitin‐like components in the developing ovaries of adult L. lineolaris are a target of IGRs such as novaluron, but its activity is specific to a critical time during development. This enhances our understanding of the effects of BPUs on adult insects and could lead to incorporation of IGRs in IPM for controlling adult insect pest populations in the field. © 2020 Society of Chemical Industry

AbstractThe neurotransmitter dopamine (DA) is known to be involved in a multitude of physiological processes. We investigated sexually dimorphic effects of disruptions in DA homeostasis and its relationship to senescence using three different Drosophila melanogaster mutants namely Catsup (Catsup26) with elevated DA levels, and pale (ple2), Punch (PuZ22) with depleted DA levels. In all genotypes including controls, DA levels were significantly lower in old (45–50‐day‐old) flies compared with young (3–5‐day‐old) in both sexes. Interestingly, females had lower DA content than males at young age whereas this difference was not observed in old age, suggesting that males had a larger decline in DA levels with age. Females, in general, were longer lived compared with males in all genotypes except ple2 mutants with depleted DA levels. This phenotype was abolished in the ple2 rescue flies. Interestingly, females also demonstrated marked age‐related decline in circadian locomotor activity compared with males. Old Catsup26 males with elevated DA levels accumulated significantly lower levels of lipid peroxidation product 4‐hydroxy 2‐nonenal (4‐HNE) compared with age‐matched wild type, ple2 and PuZ22 mutant males. In Catsup26 revertant lines this phenomenon was absent. We also observed a sexually dimorphic response in the expression levels of key stress and aging associated and/or related transcription factor genes across genotypes with elevated or depleted DA levels which was reverted to wild type levels in specific rescue lines. Taken together, our results reveal a novel sexually dimorphic involvement of DA in senescence characteristics of D. melanogaster.