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7th International Geminivirus Symposium / 5th International ssDNA Comparative Virology Workshop, Hangzhou, China 3rd – 9th November 2013.
Viruses with genomes of singlestranded (ss) DNA infect all types of organisms, including plants. The number of known ssDNA viruses has recently increased drastically facilitated by novel techniques such as rolling circle amplification (RCA) and next generation sequencing (NGS). The largest and maybe most well-studied group of ssDNA viruses is those of the family Geminiviridae that infect plants in large parts of the world. The conference 7th International Geminivirus Symposium/5th International ssDNA Comparative Virology Workshop was held the 3rd -9th of November at Zhejiang University, Hangzhou, China. The attendants came from many parts of the world with a strong representation from China. Most of the presentations covered different aspects of geminiviruses, but there were also talks and posters on plantinfecting nanoviruses as well as animalinfecting ssDNA viruses, such as parvoviruses.
It was very stimulating to listen to these presentations, look at posters and discuss with other virologists.
Recombination is an important process in geminivirus evolution. Maize streak virus (MSV) constitutes a significant problem in the maize production of Sub -Saharan Africa. The virus is native to Africa and has adapted to infect the introduced maize. As showed by Dr Adérito Monjane (University of Cape Town), maize-adapted MSV could be reconstituted in plants after inoculation with chimaeric MSV genome constructs.
Geminivirus infections are often associated with other ssDNA molecules, which are referred to as DNA satellites and which may modulate the host symptoms. A higher diversity and wider distribution of DNA satellites are now being discovered. Dr Jesús Navas-Castillo (Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora” Malaga) presented the results of screens using RCA where novel small DNA-satellitelike molecules were detected in samples of different plants from Cuba, Venezuela and Spain. These satellites were a quarter the size of a begomovirus DNAcomponent and did not contain any open reading frames. The detection of similar satellites in Florida was shown in the talk by Dr Aurora Londoño (University of Florida) confirming that they are commonly occurring.
For establishing infection, geminiviruses use and manipulate multiple host cellular pathways. The plant host will as a consequence direct different types of defences. As an example, Prof. Linda Hanley-Bowdoin (North Carolina State University) and Dr Tatjana Kleinow (University of Stuttgart) showed that geminivirus and DNA satellite proteins are phosphorylated. Generated phosphorylation- mimic mutations of the viral proteins affected their function and in some cases resulted in virus inhibition.
Dr Moshe Lapidot (Volcani Center, Israel) showed the identification of the recessive resistance gene ty-5, which confers resistance against Tomato yellow leaf curl virus (TYLCV). The gene encodes a tomato homologue of the protein Pelota. In yeast, Pelota has been implicated in ribosome recycling complexes. Overexpression of the susceptible allele of the gene in resistant tomato plants made them susceptible to TYLCV, and silencing of the susceptible allele resulted in TYLCV resistance. This is one of the first genes characterised for geminivirus resistance.
Viruses have an intricate interaction with their vectors. It has recently been shown that begomoviruses can influence both the plant host and the insect vector to promote transmission. Prof.
Shu-Sheng Liu (Zhejiang University) demonstrated how infection by Tomato yellow leaf curl China virus and its associated betasatellite down regulates the host plant’s defence against the whitefly vector by suppressing jasmonic acidrelated defences and repressing terpenoid synthesis.
These meetings are organised every third year and after presentations from different possible locations, the next meeting was decided to be held in New Delhi, India, 6th – 11th of November 2016.
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, Uppsala.
