Tomato apical stunt viroid.

Tomato apical stunt viroid (TASVd) is a serious pathogen of tomato. Pathways for introduction include tomato seedlings, tomato seeds and ornamentals. If spread to tomato, considerable losses could result. TASVd is spread easily through plant sap, e.g. during pruning and propagation, and there is some evidence of insect transmission in the greenhouse. No symptoms appear on infected ornamental solanaceous plants, but these plants can act as a reservoir for the spread of viroids in tomato production, especially in greenhouse conditions. TASVd outbreaks in tomato are rare although it has occurred in several countries in Asia, Africa and Europe. The economic impact of TASVd in tomato production is not known, but heavy yield losses may result from infection with certain strains. This viroid has not been reported as an invasive species.

Tomato apical stunt viroid.

Tomato apical stunt viroid (TASVd) is a serious pathogen of tomato. Pathways for introduction include tomato seedlings, tomato seeds and ornamentals. If spread to tomato, considerable losses could result. TASVd is spread easily through plant sap, e.g. during pruning and propagation, and there is some evidence of insect transmission in the greenhouse. No symptoms appear on infected ornamental solanaceous plants, but these plants can act as a reservoir for the spread of viroids in tomato production, especially in greenhouse conditions. TASVd outbreaks in tomato are rare although it has occurred in several countries in Asia, Africa and Europe. The economic impact of TASVd in tomato production is not known, but heavy yield losses may result from infection with certain strains. This viroid has not been reported as an invasive species.

Mixtures of insect pathogenic viruses in a single virion: towards the development of custom designed insecticides

Alphabaculoviruses (Baculoviridae) are pathogenic DNA viruses of Lepidoptera that have applications as the basis for biological insecticides and expression vectors in biotechnological processes. These viruses have a characteristic physical structure that facilitates the transmission of groups of genomes. We demonstrate that coinfection of a susceptible insect by two different alphabaculovirus species results in the production of mixed-virus occlusion bodies containing the parental viruses. This occurred between closely related and phylogenetically more distant alphabaculoviruses. Approximately half the virions present in proteinaceous viral occlusion bodies produced following coinfection of insects with a mixture of two alphabaculoviruses contained both viruses, indicating that the viruses coinfected and replicated in a single cell, and were co-enveloped within the same virion. This observation was confirmed by end-point dilution assay. Moreover, both viruses persisted in the mixed-virus population by coinfection of insects during several rounds of insect-to-insect transmission. Coinfection by viruses that differed in genome size had unexpected results on the length of viral nucleocapsids, which differed from those of both parental viruses. These results have unique implications for the development of alphabaculoviruses as biological control agents of insect pests. IMPORTANCE Alphabaculoviruses are used as biological insecticides and expression vectors in biotechnology and medical applications. We demonstrate that in caterpillars infected with particular mixtures of viruses, the genomes of different baculovirus species, can be enveloped together within individual virions and occluded within proteinaceous occlusion bodies. This results in the transmission of mixed-virus populations to the caterpillar stages of moth species. Once established, mixed-virus populations persist by coinfection of insect cells during several rounds of insect-to-insect transmission. Mixed-virus production technology opens the way to the development of custom-designed insecticides for control of different combinations of caterpillar pest species.

A Plant Bacterial Pathogen Manipulates Its Insect Vector's Energy Metabolism

ABSTRACT Insect-transmitted plant-pathogenic bacteria may alter their vectors' fitness, survival, behavior, and metabolism. Because these pathogens interact with their vectors on the cellular and organismal levels, potential changes at the biochemical level might occur. “Candidatus Liberibacter asiaticus” (CLas) is transmitted in a persistent, circulative, and propagative manner. The genome of CLas revealed the presence of an ATP translocase that mediates the uptake of ATP and other nucleotides from medium to achieve its biological processes, such as growth and multiplication. Here, we showed that the levels of ATP and many other nucleotides were significantly higher in CLas-infected than healthy psyllids. Gene expression analysis showed upregulation for ATP synthase subunits, while ATPase enzyme activity showed a decrease in ATPase activity. These results indicated that CLas stimulated Diaphorina citri to produce more ATP and many other energetic nucleotides, while it may inhibit their consumption by the insect. As a result of ATP accumulation, the adenylated energy charge (AEC) increased and the AMP/ATP and ADP/ATP ratios decreased in CLas-infected D. citri psyllids. Survival analysis confirmed a shorter life span for CLas-infected D. citri psyllids. In addition, electropenetrography showed a significant reduction in total nonprobing time, salivation time, and time from the last E2 (phloem ingestion) to the end of recording, indicating that CLas-infected psyllids were at a higher hunger level and they tended to forage more often. This increased feeding activity reflects the CLas-induced energetic stress. In conclusion, CLas alters the energy metabolism of its psyllid vector, D. citri, in order to secure its need for energetic nucleotides. IMPORTANCE Insect transmission of plant-pathogenic bacteria involves propagation and circulation of the bacteria within their vectors. The transmission process is complex and requires specific interactions at the molecular and biochemical levels. The growth of the plant-pathogenic bacteria in the hemolymph of their vectors indicated that the hemolymph contains all the necessary nutrients for their growth. In addition to nutrients, “Candidatus Liberibacter asiaticus” (CLas) can take up energetic nucleotides, such as ATP, from its vector, Diaphorina citri, using ATP translocase. In this study, we found that the CLas pathogen manipulates the energy metabolism of its insect vector. The accumulation of ATP in CLas-infected D. citri psyllids indicated that CLas induces ATP production to fulfill its need for this energetic compound. As a result of ATP accumulation, a shorter life span and altered feeding behavior were observed. These findings increase our knowledge of insect transmission of the persistent-circulative-propagative type of plant pathogens vectored by insects.