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Advances in Plant Virology Conference, Harrogate, England, 1-3 April 2009
The conference ‘Advances in Plant Virology’ was held 1-3rd of April at the Har rogate International Centre, England. This conference is organised every 18 months by The Association of Applied Biology and it functions like a European plant virology meeting. When arriving, we were greeted by some magnificent spring weather. However, the conference organisers led by John Walsh (University of Warwick) had managed to put together a very interesting programme, which was good enough to keep us inside despite the tempting spring sun. The conference had attracted 75 participants from 13 countries in Europe as well as from Costa Rica, China, India, Korea, Turkey and USA. The talks and posters covered a wide range of topics related to plant vi ruses : molecular plant -vi rus interactions, characterisations of new viruses, viruses as vectors, insect transmission, detection, etc. The programme included four invited speakers: Herman Scholthof (Texas A&M University, USA), Stephane Blanc (INRA-CIRAD, Montpellier, France), Mark Tepfer (ICGEB Biosafety Outstation, Roncade, Italy) and Claude Fauquet (Donald Danforth Plant Science Centre, St Louis, USA). It was very st imulating to listen to these presentations, look at posters and talk with other plant virologists. Plant virology is not a large subject (even if my subjective opinion is that it is the most interesting) and it was great to be in such an environment for a few days.
Most plant viruses depend on vectors for transmission. However, the interactions between plant host, vector and virus are poorly understood at the molecular level. The talk by Dr Blanc revealed an intricate mechanism for acquisition of Cauliflower mosaic virus (CaMV) by its aphid vector. The viral proteins P2 and P3 are associated with the semi-persistent transmission of CaMV. They are produced in virus factories and are then transported with microtubules to structures called transmission bodies. The results showed that when the aphid stylet punctures the cell, this activates the transmission body, which is necessary for efficient transmission. P2 is toxic to the plant cells and it is stored in the transmission bodies not to kill the cells. Microtubules polymerise and transport P2 when the aphid has started feeding.
Begomoviruses and their associated satellite-like DNA molecules cause significant disease in many crops. Dr Fauquet demonstrated the complex nature of these pathogens. A mixed infection of African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV) causes much stronger disease symptoms than any of them alone. It was shown that they have two different repressors of RNA silencing, AC4 in ACMV and AC2 in EACMCV, that are responsible for the synergistic effect. AC4 is a fast suppressor, acting late in signalling, while AC2 is a long-lasting suppressor acting early in signalling.
New begomoviruses with DNA-A, DNA-B and associated DNA-α and DNA-β satellites were identified in wild species of cotton in Pakistan. Recombination was common in all these DNA molecules. Interestingly, the Rep protein of DNA-α was found to be a strong suppressor of RNA silencing. New types of begomovirus satellites (SatDNAII and SatDNAIII) were detected in cassava in Tanzania. These satellites can use different begomovirus helper viruses and are associated with the breakdown of begomovirus resistance in cassava.
Rachel Glover (FERA, York, UK) showed the power of large-scale sequencing for virus identification. Next-generation sequencing together with metagenome analysis was used to produce a large number of cDNA sequences from virusinfected plants. The method was first tested for a tomato plant infected with Pepino mosaic virus, and it was then used to identify a new cucumovirus, Gayfeather mild mottle virus, originating from Liatris spicata. Andy Maule (John Innes Centre, Norwich, UK) led a discussion on the future direction of plant virology. Amongst the research gaps identified were an understanding of virus-vector population dynamics, insect resistance, mechanisms of resistance gene action, model to crop translation, and GM crops.
On Thursday afternoon, there was a set of nine short oral presentations by PhD students. The presentations were overall of a very high quality and they were judged by a team led by Prof Bryan Harrison. The first prize was awarded to Kamilla Knorr (University of Aarhus, Denmark) for her talk “An evolutionary experimental approach to identify resistance breaking strains of Bean yellow mosaic virus in Pisum sativum”. The second prize was given to Eva Thuenemann (John Innes Centre, Norwich, UK) for her talk “Virus-like particle production using a cowpea mosaic virus-based vector system”.
Also, the ten student posters were assessed by a team led by Prof Roger Hul l . The winner was Kimmo Rantalainen (University of Helsinki, Finland) followed by Ruth Castro Vasquez (Universidad de Costa Rica).
I would like to thank BSPP for providing the travel grant, which helped me to attend this stimulating conference.
Anders Kvarnheden, Swedish University of Agricultural Sciences