Use of polymerase chain reaction (PCR) to study transmission of banana bunchy top virus by the banana aphid (Pentalonia nigronervosa)

Banana bunchy top virus (BBTV) is a ssDNA virus transmitted by the banana aphid, ( Pentalonia nigronervosa ). A polymerase chain reaction (PCR) assay was used to study BBTV transmission efficiency, to determine the minimum acquisition-access period, the minimum inoculation-access period, the retention time, and to examine the possibility of transovarial transmission in this vector. BBTV was acquired by banana aphids within 4 h and was transmitted within 15 min feeding. On average, more than 65% of single viruliferous adult aphids transmitted BBTV. The aphids retained BBTV for their adulthood of 15–20 days. None of the 131 offspring from adult aphids reared on infected bananas were BBTV positive. Aphid transmission experiments were conducted to determine if taro and gingers are hosts of BBTV. None of the 87 taro and ginger plants exposed to aphid inoculation were infected by BBTV. The BBTV-free status of these plants was verified by PCR assay for 6 months post-inoculation. In addition, none of the taro and ginger samples collected from fields adjacent to BBTV-infected banana plants tested positive for BBTV.     

Differential expression of pathogenesis-related proteins and defense enzymes in banana: interaction between endophytic bacteria,Banana bunchy top virus and Pentalonia nigronervosa

Banana bunchy top disease caused by Banana bunchy top virus is the most serious viral disease of banana and plantain worldwide. The virus is transmitted by the aphid vector Pentalonia nigronervosa in a persistent manner. This paper deals with the effect of the interaction between plant growth promoting endophytic bacteria, Banana bunchy top virus, and the banana aphid Pentalonia nigronervosa in the expression of Pathogenesis-related proteins (PR-proteins) and defense enzymes in banana. The existence of virus in the aphids was confirmed by ELISA, DIBA and PCR. PCR could amplify 1100-bp replicase gene of BBTV from viruliferous aphids. A significant increase in the enzymatic activity of all measured PR proteins and defense enzymes, as compared to control plants, was seen in the plants inoculated with endophytic bacteria and challenged with viruliferous aphids. Native gel electrophoresis revealed expression of more isoforms of PR proteins viz., peroxidase and chitinase in the banana plants challenged with mixtures of plant growth promoting endophytic bacteria and viruliferous aphids. Enhanced activity of a PR-2 protein viz., β-1,3-glucanase was also noticed in the viruliferous aphids infested plants. Some of the defense-related enzymes viz., Polyphenol oxidase and Phenylalanine ammonia lyase and phenolic compounds were also upregulated, up to 5 days after aphid infestation and thereafter there was a reduction in the enzymatic activity. Thus, there exist a differential accumulation of PR proteins and defense-related enzymes, when there is tri-tropic interaction between endophytic bacteria, virus, and insect and the role of the endophytic bacteria in the defense mechanisms against insect pests needs to be elucidated.     

Quantification and cellular localization of dopamine in the salivary gland of the ixodid tick Amblyomma hebraeum

Dopamine (DA) content of the salivary glands in partially fed female and fed male ticks, Amblyomma hebraeum Koch (Acari: Ixodidae), was measured by high-performance liquid chromatography with electrochemical detection or by a radioenzymatic assay for catecholamines following experimental treatment. Some glands were held in vitro for up to 3 days. Other preparations (backless explants) allowed one side to be surgically denervated, the contralateral side serving as control. Normal ticks were sampled for up to 4 days post-removal from the host (rabbits). In the backless explants, there was little if any difference in DA content between denervated and control sides, even after 4 days in vitro, indicating that unilateral denervation did not eliminate the major salivary gland pool of DA. High doses of reserpine (333 g per g body weight) and 6-hydroxydopamine (1000 g per g body weight) did not significantly reduce the DA content of the salivary gland, also suggesting that only a minor component of the DA pool is within axons innervating the salivary gland. A dispersed population of cells rich in tyrosine hydroxylase immunoreactivity (an enzyme marker for catecholamine-synthesizing cells) was found in close association with the granular acini. This further suggests that the major DA pool in the salivary gland may be in cells other than the dopaminergic nerves arising from the central nervous system. © Rapid Science Ltd. 1998     

Characterization and description of a virus causing salivary gland hyperplasia in the housefly,Musca domestica

Abstract. A double-stranded DNA virus was isolated from hyperplasic salivary glands of male and female houseflies, Musca domestica L. (Diptera: Muscidae), collected from a dairy in Alachua County, Florida, U.S.A. Sodium dodecyl sulphate (SDS)–polyacrylamide gel electrophoresis (PAGE) of this housefly salivary gland hyperplasia (SGH) virus revealed the presence of two major and eight minor structural polypeptides. Restriction endonuclease analysis indicated that the c. 137 kilobase pair DNA was double-stranded. Weekly sweep-net sampling of the fly population throughout the season (May-October, 1991) showed that 1.5-18.5% of the dissected flies possessed hyperplasic salivary glands. The virus replicated within the nuclei of the salivary gland cells and was transmitted per os to newly-emerged healthy adult flies.     

Ultrastructural investigation of a salivary gland in a centipede: structure and origin of the maxilla I-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora)

The maxilla I-gland of Scutigera coleoptrata was investigated using light and electron microscopy methods. This is the first ultrastructural investigation of a salivary gland in Chilopoda. The paired gland opens via the hypopharynx into the foregut and extends up to the third trunk segment. The gland is of irregular shape and consists of numerous acini consisting of several gland units. The secretion is released into an arborescent duct system. Each acinus consists of multiple of glandular units. The units are composed of three cell types: secretory cells, a single intermediary cell, and canal cells. The pear-shaped secretory cell is invaginated distally, forming an extracellular reservoir lined with microvilli, into which the secretion is released. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cell. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the structure of the glandular units of the salivary maxilla I-gland is comparable to that of the glandular units of epidermal glands. Thus, it is likely that in Chilopoda salivary glands and epidermal glands share the same ground pattern. It is likely that in compound acinar glands a multiplication of secretory and duct cells has taken place, whereas the number of intermediary cells remains constant. The increase in the number of salivary acini leads to a shifting of the secretory elements away from the epidermis, deep into the head. Comparative investigations of the different head glands provide important characters for the reconstruction of myriapod phylogeny and the relationships of Myriapoda and Hexapoda.     

Distribution of velvet tobacco mottle virus in its mirid vector and its relationship to transmissibility

Following acquisition by feeding, velvet tobacco mottle virus (VTMoV) was detected in the gut, haemolymph and faeces of the mirid vector, Cyrtopeltis nicotianae, but not in the salivary glands. Virus antigen was detected in the gut and haemolymph for up to nine days following acquisition. Infective virus was detected in the secretions and excretions of the mirids immediately after acquisition and was also detected in the faeces of nymphs after six days. Insoluble nigrosin dye was eliminated intermittently from the gut up to six days after ingestion, in a manner similar to the loss of virus infectivity. Non-infective mirids were able to inoculate plants from infectious sap deposits on the upper epidermis. An ingestion-defecation model of insect transmission in which the salivary glands are not implicated is proposed as one explanation for the persistence of transmission in this mirid-virus association.     

MCK2-mediated MCMV infection of macrophages and virus dissemination to the salivary gland depends on MHC class I molecules

1. Download : Download high-res image (175KB)
2. Download : Download full-size image

     

Intron-mediated enhancement of the banana bunchy top virus DNA-6 promoter in banana (Musa spp.) embryogenic cells and plants

 Intron-containing fragments derived from the 5′ untranslated regions of the maize ubi1, maize adh1, rice act1 and sugarcane rbcS genes were tested for their enhancing effects on the banana bunchy top virus DNA-6 promoter (BT6.1) in banana (Musa spp. cv. Bluggoe) embryogenic cells. The rice act1 and maize ubi1 introns provided the highest levels of intron-mediated enhancement of GUS expression, increasing native BT6.1 promoter activity by about 300-fold and 100-fold, respectively. The sugarcane rbcS intron increased expression about tenfold, whereas the adh1 intron had no significant effect. In regenerated transgenic banana plants, the ubi1 intron significantly enhanced BT6.1 promoter activity to levels similar to that of the CaMV 35 S promoter and did not appear to affect the tissue specificity of the promoter. Received: 28 July 2000 / Revision received: 21 August 2000 / Accepted: 4 October 2000     

Effects of diet and mating status upon corpus allatum activity, oocyte growth, and salivary gland size in the ring-legged earwig

The effect of diet on mating behavior and the subsequent effects of diet and mating status on the biosynthesis of juvenile hormone III, basal follicle length, salivary gland size and total body weight were assessed in the ring-legged earwig, Euborellia annulipes (Lucas) (Family Carcinophoridae; subfamily Carcinophorinae) during the first 15 days of adult life (the first gonadotrophic cycle of those fed presumably near-optimal diets of catfood) and again on day 25 (late vitellogenesis of the second gonadotrophic cycle of those fed catfood). Diets of catfood, honey, fructose and total starvation, respectively, imposed on 0-day adult females did not affect sexual receptivity, mating success or duration of mating as assessed on day 7. With the addition of a group of virgin, catfood fed females, we noted that only those females maintained on catfood oviposited within 25 days; enforced virginity virtually abolished oviposition. Total food deprivation of females as well as diets of honey or fructose abolished the cycles in total body weight, basal follicle length, salivary gland size and juvenile hormone production. Thus, starvation decreased the reproductive success of these insects, and carbohydrates only (fructose) or in combination with trace amounts of nutrients and protein (honey) were not sufficient to promote reproduction and associated cycles in this insect. Furthermore, virgins failed to undergo the decreases in salivary gland size that were characteristic of mated females. Among mated, catfood-fed females, the second cycle in juvenile hormone production appeared to be smaller than the first.     

Midgut and salivary gland barriers to La Crosse virus dissemination in mosquitoes of the Aedes triseriatus group

Vector competence for La Crosse virus (LACV) was compared for four species in the Aedes (Protomacleaya) triseriatus group: Ae. triseriatus (Say), Ae. hendersoni Cockerell, Ae. zoosophus Dyar and Knab and Ae. brelandi Zavortink (Diptera: Culicidae). Rates of replication and dissemination of virus in the mosquito hosts were compared and rates of oral transmission of virus to suckling mice were determined. Barriers to virus dissemination which limited the ability of each species to transmit virus were identified. Ae. zoosophus displayed the highest vector competence for LACV. Both infection and transmission rates were high: 99% and 85% respectively; no significant barriers to LACV were found. Disseminated infection of Ae. triseriatus with LACV was controlled primarily be a midgut escape barrier. When virus was introduced directly into the haemocoel, transmission rates were significantly increased (37% v. 79%). Ae. hendersoni showed high susceptibility to LACV infection but a very low rate of oral transmission (7%). Ae. brelandi was also highly susceptible to infection by LACV and transmitted virus at an intermediate rate (27%). Modulation of vector competence in both Ae. hendersoni and Ae. brelandi resulted from a salivary gland escape barrier. As these four species of mosquitoes comprise a closely related monophyletic series, their differences of vector competence for LACV provide an excellent model for studying the genetic basis of the barriers involved.     

A cellular hierarchy of Notch and Kras signaling controls cell fate specification in the developing mouse salivary gland

1. Download : Download high-res image (215KB)
2. Download : Download full-size image

     

BhSGAMP‐1, a gene that encodes an antimicrobial peptide,is developmentally regulated by the direct action of 20‐OH ecdysone in the salivary gland of Bradysia hygida (Diptera,Sciaridae)

Recently we have shown that BhSGAMP‐1 is a developmentally regulated reiterated gene that encodes an antimicrobial peptide (AMP) and is expressed exclusively in the salivary glands, at the end of the larval stage. We show, for the first time, that a gene for an AMP is directly activated by 20‐OH ecdysone. This control probably involves the participation of short‐lived repressor(s). We also found that the promoter of BhSGAMP‐1 is not equipped with elements that respond to infection, provoked by the injection of microorganisms, in the salivary glands or in the fat body. We produced polyclonal antibodies against the synthetic peptide and found that the BhSGAMP‐1 peptide is secreted in the saliva. The BhSGAMP‐1 gene was also activated during the third larval molt. These facts confirm our hypothesis that this preventive system of defense was selected to produce an environment free of harmful microorganisms in the insect's immediate vicinity, during molts. genesis 47:847–857, 2009. © 2009 Wiley‐Liss, Inc.     

A Drosophila salivary gland mucin is also expressed in immune tissues: evidence for a function in coagulation and the entrapment of bacteria

Our studies on the developmental regulation of glycosylation in Drosophila melanogaster led us to identify and characterize gp150, an ecdysone-regulated mucin that is found in hemocytes, the gut (peritrophic membrane) and in the salivary glands. We are particularly interested in mucin immune functions and found that gp150 is released from larval hemocytes, becomes part of the clot and participates in the entrapment of bacteria. By RT-PCR and RNAi experiments, we identified gp150 as the previously described I71-7, an ecdysone-induced salivary glue protein. We discuss the evolutionary and biochemical implications of the dual use of salivary proteins for immune functions in insects. Further molecular characterization of such shared proteins may enable a better understanding of the properties of proteins involved in containment and elimination of microbes, as well as hemostasis and wound repair.     

Biology of the European large raspberry aphid (Amphorophora idaei): its role in virus transmission and resistance breakdown in red raspberry

1 The European large raspberry aphid Amphorophora idaei Börner is the most important vector of viral diseases afflicting commercially grown red raspberry ( Rubus idaeus L.) in Northern Europe, with European raspberry production amounting to 416 000 tonnes per annum. This review synthesizes existing knowledge on its biology and interactions with other organisms, including its host plant and the viral pathogens it vectors.
2 Information about trophic interactions with other insect herbivores and natural enemies is reviewed. Vine weevils Otiorhynchus sulcatus compromise aphid resistance in some raspberry cultivars, increasing A.   idaei abundance by 80%. Parasitoids show mixed success in parasitizing A.   idaei , although Aphidius ervi attack rates more than doubled when A.   idaei fed on a partially susceptible raspberry cultivar, compared with a resistant variety. These findings are discussed in the context of potential biological control as part of an integrated pest and disease management framework.
3  Amphorophora idaei transmits four known viruses: Black raspberry necrosis virus, Raspberry leaf mottle virus, Raspberry leaf spot virus and Rubus yellow net virus , with A.   idaei taking as little as 2 min to transmit some viruses.
4 Existing control strategies, including resistant cultivars, insecticides and eradication of disease from parent plants, are described. In particular, strong selection pressures have resulted in A .  idaei overcoming genetic resistance in many raspberry cultivars and most insecticides are now ineffective.
5 Future directions for the sustained control of A.   idaei are suggested, taking into consideration the possible effects of climate change and also changes in agronomic practices in U.K. agriculture.