Various flavonoid types are known to confer resistance toward insect attack in several plant species. Thus, a C-glycosyl flavone isolated from the silk of a resistant variety of maize was shown to inhibit the growth o fthe corn earworm,Helio this zea[ 1, 2], and O-glycosyl flavones and aglycones are significant factors against the development of Heliothis virescens, H. zea and Pectinophora gossypiella on cotton flower buds [3, 4]. Similarly, flavonoid tannins are implicated as insect resistance factors of the oak tree and of the cotton plant as well [5, 6]. However, the pentahydroxy flavone, morin, which occurs naturally in mulberry actually stimulates the consumption of artificial diets by silkworm moth larvae [7], and a glycosylated flavone has also been shown to be responsible for the feeding of Agasicles beetles on alligatorweed [8]. Up to now only a relatively small number of structural variants among the flavonoids has been examined by insect bioassay, and an interpretation of these structural features has not been forthcoming. In order to clarify this topic, we

Flavonoids as larval growth inhibitors. Structural factors governing toxicity.

Antiviral activity of a serine protease from the digestive juice of Bombyx mori larvae against nucleopolyhedrovirus.

The genus Baculovirus contains three subgroups of viral types: (1) nuclear polyhedrosis viruses (NPVs), (2) granulosis viruses (GVs), and (3) nonoccluded baculoviruses. While little information is available for viruses from the third subgroup, several aspects of the infectivity and mode of action of NPVs and GVs have been studied. The most common route of entry of a virus into an insect host is per os, and both virus types enter midgut cells (primary site of infection) by membrane fusion. However, two distinct mechanisms of virus uncoating occur among the baculoviruses: NPVs uncoat within the nucleus, whereas GVs uncoat at the nuclear pore complex. Baculoviruses of subgroup 3 appear to uncoat by either mechanism. In addition to replicating within the nucleus, NPV inoculum virus may pass through the intestinal epithelium immediately after ingestion, thereby establishing a systemic infection of the hemocoel prior to virus replication in midgut cells. The GVs do not appear to pass through midgut cells as rapidly as NPVs and in general, the developmental cycle of GVs is longer than that of NPVs. NPVs have been grown in cell culture while GVs have not.

Infectivity and mode of action of Baculoviruses

To gain an insight into the effects of different diets on growth and development of the domesticated silkworm at protein level, we employed comparative proteomic approach to investigate the proteomic differences of midgut, hemolymph, fat body and posterior silk gland of the silkworms reared on fresh mulberry leaves and on artificial diet. Seventy-six differentially expressed proteins were identified by MALDI TOF/TOF MS, and among them, 41 proteins were up-regulated, and 35 proteins were downregulated. Database searches, combined with GO analysis and KEGG pathway analysis revealed that some hemolymph proteins such as Nuecin, Gloverin-like proteins, PGRP, P50 and beta/-N-acetylglucosamidase were related to innate immunity of the silkworm, and some proteins identified in silkworm midgut including Myosin 1 light chain, Tropomyosin 1, Profilin, Serpin-2 and GSH-Px were involved in digestion and nutrition absorption. Moreover, two up-regulated enzymes in fat body of larvae reared on artificial diet were identified as V-ATPase subunit B and Arginine kinase which participate in energy metabolism. Furthermore, 6 down-regulated proteins identified in posterior silk gland of silkworm larvae reared on artificial diet including Ribosomal protein SA, EF-2, EF-1gamma, AspAT, ERp57 and PHB were related to silk synthesis. Our results suggested that the different diets could alter the expression of proteins related to immune system, digestion and absorption of nutrient, energy metabolism and silk synthesis poor nutrition and absorption of nutrition in silkworm. The results also confirmed that the poor nutrient absorption, weakened innate immunity, decreased energy metabolism and reduced silk synthesis are the main reasons for low cocoons yield, inferior filament quality, low survival rate of young larvae and insufficient resistance against specific pathogens in the silkworms fed on artificial diet.

Comparative proteomic analysis between the domesticated silkworm (Bombyx mori) reared on fresh mulberry leaves and on artificial diet.

The susceptibility of noctuid larvae to baculoviral infection is markedly affected by phytochemicals ingested during the acquisition of viral inoculum on foliage We hypothesized that a major process causing phytochemical inhibition of viral disease is phenolic oxidation by phenolases, particularly peroxidase (POD), which subsequently generates free radicals To test this hypothesis, we manipulated the chemical interactions in foliage of cotton, tomato, and lettuce by application of antioxidants, prooxidants, enriched extracts of phenolases, and/or phenolic substrates Larvae of Heliothis virescens or Helicoverpa zea that received viral inoculum on treated foliage were less likely to die from viral infection the higher the POD activity of this foliage Furthermore, the higher the POD activity, the more free radicals were generated in crushed foliage, and the more free radicals generated, the lower the incidence of viral disease We present a series of reactions hypothesized to lead to inhibition of viral disease by free radicals, the generation of which is mediated, at least in part, by POD Phenolic redox cycling catalyzed by POD involving clastogenesis (generation of H2O2) appeared to be a critical driver of phytochemical reactions leading to free radical generation and inhibition of baculoviral disease in their noctuid hosts We also report application of an assay for the detection of free radicals by using methemoglobin as a new modification of this method for detecting radicals in plant foliage in the immediate aftermath of an oxidative burst

http://static.vtc.vt.edu/media/documents/1998_Hoover_et_al_Inhibition_of_Baculoviral_Disease.pdf

Inhibition of baculoviral disease by plant-mediated peroxidase activity and free radical generation

カイコ幼虫の中腸および消化液中にみられる赤色けい光性たんぱくRFP生成にはカイコ中腸起源のたんぱく質と緑葉クロロプラスト中のクロロフィルaと一酵素たんぱく質との三者が必要であり,しかして,まず最初にクロロフィルaに酵素が作用して色素が生成し,この色素が中腸起源たんぱく質と作用してRFPになる。この既報の生成機構に次の二点を加えた。1) クロロフィルaから変性した色素はクロロフィリドaであり,しかしてクロロプラスト起源のたんぱく質はクロロフィラーゼである。なおこの反応はカイコ幼虫消化液のpHと同じアルカリ性下で進行する。2) 中腸起源たんぱく質とクロロフィリドaとの作用でRFPが生成する過程で光が関与している。なおこの反応はカイコ幼虫中腸組織のpHとほぼ同じpH下で進行する。

https://www.jstage.jst.go.jp/article/jjaez1957/20/1/20_1_37/_pdf

The Mechanism of Formation of the Red Fluorescent Protein in the Digestive Juice of Silkworm Larvae

The silkworm larvae reared on artificial diet were more susceptible to the infection per os with nuclear polyhedrosis virus than those reared on natural diet and furthermore the anti-viral activity in the digestive juice of the former was weaker than that of the latter. The fluorescent colours of the digestive juices from the larvae fed on natural or artificial diets, were different from each other, being red in the former and yellow in the latter. A protein having red fluorescence was fractionated from the digestive juice of silkworm larvae fed on natural diet, mulberry leaves. The fluorescent protein fraction inactivated the nuclear polyhedrosis virus and the inactivating potency was almost same both in the digestive juice and in the buffered solution containing this fluorescent protein fraction at nearly equal concentration of that in the digestive juice itself. It is concluded that this red fluorescent protein fraction may play an important role in the protective mechanism in silkworm larvae for per os infection by the silkworm nuclear polyhedrosis virus and that the fraction is not observed in the digestive juice from the larvae reared on artificial diet.

https://www.jstage.jst.go.jp/article/jjaez1957/12/4/12_4_189/_pdf

Inactivation of Nuclear Polyhedrosis Virus in the Digestive Juice of Silkworm Larvae, Bombyx mori L.

The Production of Anti-Viral Substance, a Red Fluorescent Protein, in the Digestive Juice of the Silkworm Larvae (Lepidoptera : Bombycidae)

カイコ幼虫消化液中に存在する抗ウィルス性赤色けい光たんぱく質(RFP)の生成機構に関して,主としてin vitroの実験系でおこなった前報までの研究成果で,その生成過程に光の存在が必須であることがわかった。本研究では,カイコ幼虫の飼育に明および暗の両区を設定して飼育し,消化液中のRFPの定量をおこなった。その結果,生体内においてもRFPの生成に光が関与していることが明らかとなった。次に既報のように,RFPがウィルス不活化作用を有していることから,上記明暗両区で飼育したカイコに核多角体病ウィルスを接種し,発病率を調べたところ,明区のカイコは暗区のそれにくらべて抵抗力を有することがわかった。しかして,この抵抗力の差は明区と暗区でRFPの産生量が異なることに原因すると推察した。

Comparison of Anti-viral Activities of the Silkworm Larvae Reared in Light and in Darkness in Relation to the Formation of Red Fluorescent Protein (RFP)

家蚕を桑粉またはその抽出物を全く含まない人工飼料で,蟻蚕より営繭,産卵までの全令飼育をおこなった. 5令起蚕までの減蚕は5%, 5令起蚕に死亡蚕があり,約60%が上簇し,営繭を全うしたものは約50%であった. 前報の飼育成績に比べて向上した点は,特にアセチルコリンおよび王乳の添加により,飼料を強化したためと考えられる.コリンおよびアセチルコリンが脱皮促進効果を有すること,および王乳はコリン類以外に栄養価にとむ物質が含まれることを指摘した.

https://www.jstage.jst.go.jp/article/nogeikagaku1924/37/12/37_12_735/_pdf

Jun Nishida

Papers

The Mechanism of Formation of the Red Fluorescent Protein in the Digestive Juice of Silkworm Larvae

Inactivation of Nuclear Polyhedrosis Virus in the Digestive Juice of Silkworm Larvae, Bombyx mori L.

The Production of Anti-Viral Substance, a Red Fluorescent Protein, in the Digestive Juice of the Silkworm Larvae (Lepidoptera : Bombycidae)

Comparison of Anti-viral Activities of the Silkworm Larvae Reared in Light and in Darkness in Relation to the Formation of Red Fluorescent Protein (RFP)

Silkworm Rearing on Artificial Diet