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HPIS 2017 – 3rd Hemipteran-Plant Interaction Symposium, Madrid, Spain, 4th – 8th June 2017
Hemiptera is an insect order that includes from 50,000 to 80,000 species, comprising cicadas, aphids, leafhoppers and planthoppers, among other. The vast majority of the hemipterans feed on plants and establish different types of ecological relationships with their hosts. Hemipterans can produce severe harm to their plant hosts either because they suck the plant sap or because they can transmit viruses or pathogenic bacteria. Therefore, the characterisation of the ecology and epidemiology and the management strategies of many important plant diseases require knowledge about the interactions between the pathogens, the plant and the insect vector. The HPIS 2017 meeting addresses this particular area of research, in which entomology and phytopathology meet.
One of the aspects that called my attention was the wide variety of questions that are being addressed using oomic approaches. For example, comparative genomics has been used to infer the basis of generalism in aphids, to study the expression of predicted secreted proteins of salivary glands of aphids and their role as disease or vector effectors or to characterise single insect transcriptomes of whiteflies from different populations. Also, the feeding insect behavior of two pentatomids was studied by proteomic analysis of their salivary glands and the transcriptome changes of Bemisia tabaci in response to feeding in plants infected with a Crinivirus. Oomics also revealed that female and male adults of Diaphorina citri responded similarly to exposure to ‘Ca. Liberibacter asiaticus‘ and in a different work the protein effectors that allow the invasion of the psyllid Diaphorina citri gut and salivary glands by this pathogen, were amply described. The effect of RNA viruses in the efficiency of RNAi in aphids was addressed by sequencing the small RNAs and transcriptome of three species of aphids. Later, miRNAs that targeted specific genes were introduced and the effect of silencing measured in relationship with the virus infections. The use of miRNAs to silence gene expression in insect vector appears as the preferred tool for several studies.
A very remarkable discovery for me was the EPG (electrical penetration graph monitoring) technique which allows the observation and quantification of the otherwise invisible feeding behavior of piercing-sucking arthropods. This technique reveals the steps of the stylet pathway during insect feeding and transmission of virus or bacteria to host plants. Using this technique, it was shown that the colonisation of the insect vector by Xylella fastidiosa increases the probability of successful inoculation behavior, the type of specific punctures that aphids have produce to transmit Beet yellows virus, the detailed process of stylet penetration and sieve element occlusion that leads to compatible or incompatible aphid plant interactions and the role of plant volatiles in the preference of hosts plants by aphids. Very importantly, evidence was presented of the ability of Scaphoideus titanus to feed on the xylem, the insect vector of Flavescence doree phytoplasma to grapevines in Europe that is usually considered a mesophyll feeder. This makes S. titanus a candidate vector for transmission of xylem pathogens such as X. fastidiosa.
Other very interesting information was related to the characterisation of the bacteriome, the ecologic role of symbiotic bacteria, acquisition means by insect vectors and the fitness consequences of the presence of these bacteria for the insect survival and its ability to transmit pathogens. The evidence suggests the important role of these bacteria in the life of the insect but also appears as possible source of biological control and of modulation of pathogen transmission.
A group of presentations focused on the intimate details of insect-virus-plant interactions and in many cases addressed the problem of multitrophic relationships between the participants of these pathosystems. Remarkable results showed that in some pathosystems the insect vector fitness increases when infected with its associated pathogen, in cases such as: wheat – Barley yellow dwarf virus – Rhopalosiphum padi in a water dependent manner, in two brassicae plants – Turnip yellows virus — Myzus persicae in a plant species manner, in citrus – ‘Phytoplasma aurantifolia‘ — Diaphorina citri and in Arabidopsis thaliana – Aster yellows phytoplasma – Dalbulus maidis pathosystems. In this last case, it was also shown that phytoplasmas modulate the non-host resistance by introducing effector proteins to the host plants.
Additionally, the proteins and molecular processes involved in the specific identification of virus or bacteria and their insect vectors where described for a number of pathosystems. In particular, very interesting evidence was presented about the specific involvement of protein effectors such as MIFs (proteins of the cytokine family associated with the regulation of the immune response in animals) in aphids that seems to inhibit plant response, the Mp10 protein which suppresses the first layer of the plant defense response in aphid susceptible plants and the ability of aphid proteins to target plant proteins to favor the aphid virulence.
Finally, more traditional techniques also were used to report the presence of vectors in different part of the world, for example the identification of vectors of X. fastidiosa in Mallorca, Spain and Iberian Peninsula, psyllid vectors of ‘Liberibacter solanacearum‘ in the UK and Sweden, a revision of the aphid composition of Turkey, the composition richness and abundance of Cicadellidae in an area of Colombia, the distribution patterns of vector Philaenus spumairus of X. fastidiosa in Central Italy, among others. These evidence provides practical information needed for the management and mitigation of many diseases.
In conclusion, the meeting was fantastic because of the very specific subject it addresses, the remarkable quality of many presentations, the excellent organisation of the conference and beautiful venue at the CSIC in Madrid. I hope I will be able to put at the service of the problems that we have in Colombia the information about the last trends in the study of hemipteran vectors. The meeting was also an opportunity to meet again some colleagues and to make new contacts that will allow the progress of my line of research. Finally, I would also like to thank the BSPP for the financial support which allowed me to attend the meeting.
Liliana Franco-Lara Universidad Militar Nueva Granada, Colombia