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6th International Conference on Pseudomonas syringae pathovars and related pathogens
The conference was held in a cliffside hotel in the village of Acquafredda di Maratea, 7km south of Sapri and about 2 hours south of Naples, Italy. Getting to the hotel was quite a trek, with many people flying into Rome and then taking the 4hour train journey to Sapri. Transfer to the hotel was enough to test the strongest constitution as the road wound around the cliffs, at times 500 feet up above a sheer drop, and the hotel minibus driver was clearly in training for the Ferrari formula 1 team! However, the conference organiser Professor Nicola Iacobellis made up for the journey by doing a marvellous job of arranging the conference in a hotel with a spectacular setting and excellent facilities and for attracting, via the international organising committee, several of the world leaders in the field. Sessions were held on Monday, Tuesday and Thursday, with a social (networking, honest!) trip on the Wednesday.
Cindy Morris started proceedings on the Monday with an excellent talk that brought together aspects of both basic and applied biology for studying and combating Pseudomonas syringae pv. aptata, a serious pathogen of cantaloupe melon in France. Jean Michel Monier gave a very interesting talk describing some elegant experiments he carried out in Steve Lindows lab to study bacterial colonisation on plant leaf surfaces. By using epifluorescent microscopy, he was able to observe Gfp-expressing bacteria aggregating on leaf surfaces and this could be for optimal stress survival. Bacteria existing near veins and glandular trichomes appeared to survive better than bacteria located on other parts of the leaf.
George Sundin was asked to give an overview of how Pseudomonas syringae deals with environmental and plant-associated stresses. This was one of the best talks of the conference for me as he described, for instance, some of the genes employed by bacteria in coping with DNA damage from solar radiation. A pair of genes, rulAB, are often acquired on plasmids by Pseudomonas syringae and these act as an upgrade to the cells defences against DNA damage. They are dispensable for resistance to UV damage, but if the bacterium carries the genes then the bacteria can survive for longer than strains not carrying the genes.
Advances in the elucidation of the regulatory mechanisms behind expression of type III protein secretion genes were nicely described by Steve Hutcheson. Major progress in the understanding of negative regulators was described and clearly the challenges in this field are to understand how environmental signals are transduced to deactivate negative regulators, like Lon protease, to allow activation of the type III genes. Steve also described the finding that AvrPphD, an effector protein recognised as an avirulence determinant by some plants, has tyrosine phosphatase activity, a trait found in virulence factors of mammalian pathogens. This presents a new route for researching pathogenicity in plant pathogens as AvrPphD may be targeting MAP kinase proteins in plants.
From the offered papers, Francisco Cazorla described a nice piece of work about a very small protein (<3 Kda) called mangotoxin, which targets amino acid pathways and may be involved in the competitive inhibition of Gram-positive bacteria. Helge Weingart told us about how cma genes (invoved in coronatine toxin expression) are differentially expressed in different pathovars of P. syringae; one is temperature- dependent while the other is type III-dependent, clearly showing different strategies employed by pathogens to express virulence genes.
On the Monday night Alan Collmer organised a discussion group to address certain areas of research that required a community decision. This included the possibility of having another Pseudomonas plant pathogen genome sequenced and to try to agree a common theme for designating effector genes. The latter issue has been a major topic for years and still no unanimous decision could be reached.
On the Tuesday, we had several of the world leaders in Type III gene research, including Jean Greenberg, Barbara Kunkel, Shen Yang-He, Carol Bender and Jim Alfano, presenting. All described advances in mining genomes to fish out new effectors, to confirm that the effectors were likely to be true candidates through predictive methods and to study what the targets of effectors are. The bottom line was . Put your hard hat on, mining effectors might be a bit late – they ve done it all! . Suvi T aira presented the European effort (in collaboration with John Mansfield and Martin Romantschuk) for examining Hrp pilus biology. Zoltan Klement described the early induced resistance response of plants to pathogens that is triggered by bacterial surface molecules.
Thursday saw a mixed day, mainly dominated by diagnostics and taxonomy. Charles Manceau, Anne Willems and David Stead gave good talks describing efforts to properly classify plant pathogens with different molecular methods and Marco Scortichini and Arantxa Rico described efforts to classify P. savastanoi pv. phaseolicola and Pseudomonas avellanae, pathogens of bean and hazelnut, respectively.
The trip on Wednesday was by coach through the winding mountainous region north-west of Sapri, firstly to see how buffalo milk mozzarella is made. The farm contained 504 buffalos, of which only one lucky one was a male. The cheese was very tasty, with a yoghurt flavour. We then moved further north to Pompeii and a walk around the site for 2 hours. I found it quite a moving place, particularly when you see the plastercasts of the bodies. The site is huge (apparently it would take 2 days to get around it properly) and it is incredible just how advanced and inventive the people were for instance, they used marble as cats eyes in paths to guide themselves in the dark.
We arrived back and had a quick dinner. Then, 15 delegates took up the challenge laid down by Professor Iacobellis. A conference football team, named Dynam Syringae (courtesy Ian Brown), was to attempt to win the Acquafredda cup from the current holders, the Italian hotel staff. Manager Peter Ott and I organised a team of British, German, Hungarian, Turkish, French and American players and we congregated in Acquafredda Stadium, a clay pitch under floodlights and dominated by the mountains above us. About 60 delegates came to support us and the atmosphere was electric. It was a 7-a-side match on a sized pitch played over 60 minutes. The Italians showed their class immediately by storming into a 9-3 lead. John Mansfield soon earned himself the nickname The Cat with his gymnastic efforts keeping our goal and certainly ensured that the Italian tally wasn t higher with some brilliant saves. Fortunately, we had a couple of secret weapons. Andrew Chopper Pitman, a semi-professional player in Britain, dominated defence, midfield and attack with runs down the wing and sweeper movements. His 5 goals brought us back into the game. Then, David Jones (10 year old son of Jeff) proved to be very capable against adults and scored a cracking goal, proving that he stands a good chance of making the American national team. Bob Coutts obtained a worthy hatrick to keep Dynamo in the chase. Matthias Ullrich was an excellent referee, which was enhanced as he happened to be dressed all in black. Needless to say, we all gave him the obligatory (friendly!) abuse for missing the fouls!! The second half proved the turning point for Dynamo, as our strength in depth squad pulled back the deficit (although it did help that we played 9 players for the last 10 minutes!). George Sundin and Jim Alfano proved that Americans have a right foot with great efforts on the pitch and Boris Vinatzer was throwing himself all over (literally). In the final minute, Dynamo managed to grab a hard fought over equaliser to make it 12-12 and we were into penalties. David Jones took a pressure penalty to keep us in the game and scored probably the best of the lot, with a goal that Michael Owen would be proud of. Alas, it wasn t to be, the Italians showed they had a stronger nerve and they beat us 7-6. But the real winner was the Pseudomonas syringae community!
This event really brought everyone together, from Profs. to PhDs, and from then on the atmosphere was much more casual and relaxed. This was reflected on the final night (Thursday) when Carolee Bull asked several of us to read out limericks after the dinner, which she had compiled about the meeting. Then, 25 of us, including several Profs (not just the young uns!) went for a midnight swim and diving off a boat, off the hotel beach. All in all, this was one of the most remarkable meetings I have ever attended because of the social events having such a positive outcome on generating a better community spirit and enabling people to develop closer links in their research. The science was of an excellent standard and one of the telling points was how important genome sequencing is. So many people are utilising the genome sequences of Pseudomonas (including P. fluorescens, as described by Gail Preston) for different aspects of research and finally we are starting to see some biological data deriving from it rather than just the usual lists . The Pseudomonas syringae community is also leading the way in certain areas of research, for example Type III secretion pilus research, effector protein function and colonisation traits. The future looks very rosy indeed.
I am very grateful to BSPP for providing me with a travel award to attend this conference and present an oral paper.
Football squad (nationality and goals in parentheses): Dynamo Syringae Director: Nicola Iacobellis (Ita), Manager: Peter Ott (Hung), Goalkeeper: John Mansfield (UK), Outfield: Andrew Pitman (UK, 5), George Sundin (USA, 1 pen), Zoltan Bozso (Hung, 1), Alexander Schenk (Ger), Charles Manceau (Fra), Bob Coutts (UK, 3), Robert Jackson (UK), Helge Weingart (Ger, 1), John Thomas (UK), Jens Boch (Ger), Hassan Amouneh (UK), Jim Alfano (USA, 1+1pen), Meric Ozanak (Tur), David Jones (USA, 1+1 pen), Julian Smith (UK), Boris Vinatzer (USA).
Robert Jackson
The 6th International Conference on Pseudomonas syringae pathovars and related pathogens (September 15th-19th) was held at the hotel Villa del Mare, close to Acquafredda di Maratea, in the Basilicata region of Italy. The organisation, led by Professor Nicola Sante Iacobellis, was perfect; from the choice of the idyllic location to the scientific programme and social events. The conference was attended by 120 participants and its relatively small size provided plenty of opportunities for scientific discussions.
After the official opening ceremony, we started the scientific programme with a session on Ecology and Epidemiology. Cindy Morris gave an interesting talk on bacterial blight of cantaloupe melons (caused by P. syringae pv. aptata) in France. This disease has been considered a natural disaster in certain regions of that country and it is difficult to understand why it is so important in France and not in other producing countries. George Sundin talked about mechanisms and strategies of stress resistance, and especially about tolerance to desiccation and UV light; pathogenic strains of P. syringae seem to be more fit and able to survive under dry conditions than non-pathogenic strains. The DNA repair mechanisms of P. syringae might contribute to higher fitness and pathogenicity of some strains. In the session on pathogenesis and determinants of pathogenicity, Alan Vivian showed that it is possible to differentiate most races of P. syringae pv. pisi through multiplex PCR and explained how curing plasmids can help us to understand the pathogenicity determinants of different races. An one important conclusion of this work was that effector genes are redundant in nature. Dallice Mills also gave a very interesting talk on how the similarity between genes of the hrpM locus of P. syringae pv. syringae and the mdoA locus of Escherichia coli helped to elucidate the organisation and function of hrpM. After dinner, I attended the functional genomics workshop organised by Alan Collmer. The main issues debated were: which P. syringae strain should be sequenced next (pv. phaseolicola seems to be the best candidate), how the web site with the complete sequence of P. syringae pv. tomato DC3000 should work, and how new effector genes should be named. This last issue generated a lot of discussion.
The second day began with a session on Genetic and physiological analysis of host pathogen interactions. Barbara Kunkel gave a talk on the function of the P. syringae AvrRpt2 virulence factor. AvrRpt2 promotes virulence inside the plant cells, but it does not seem to be related to known defence genes. Barbara is now asking the question does AvrRpt2 alter auxin physiology? Zoltan Klement gave an interesting talk on early induced resistance (EIR). Pathogens and non-pathogens are able to induce EIR. In incompatible interactions, under certain conditions (e.g. high temperature), the EIR can prevent host response and the plants remain symptomless. In the session on Molecular characterisation/genomics, Gail Preston talked about the sequence of P. fluorescens and highlighted similarities between the type three secretion system (TTSS) of this species and P. syringae. And Jim Alfano concentrated on mining the genome sequence of DC3000 for hop (Hrp outer protein) genes that encode TTSS substrates. In the Disease management and control session, Larry Claflin talked about control measures for P. syringae pathovars whilst David Sands explored the possibility of using plant pathogens to control weeds; the development of bioherbicides is difficult because most pathogens are not aggressive enough to kill plant hosts. In this session, I gave a talk on bacterial canker of wild cherry. Although my talk did not generate a lot of discussion at the time, on the last day this disease was in the limelight again.
On the third day we had an excursion. After driving through the mountainous countryside north of Sapri, we visited an organic buffalo farm situated in the Campania plains. We had a tour of the farm: from the calves and the milking cows to mozzarella making. We had the opportunity of tasting cheese, yoghurts and fantastic ice creams made with buffalo milk. After a picnic lunch on the lawn we went to Pompeii, one of the most important archaeological sites in the world. We arrived back at the hotel very happy and quite tired, but the day was still not over. After dinner there was a football match between the hotel staff and conference participants. The hotel staff side dominated the first half, but the conference surprisingly recovered in the second half to draw the game at 12-12. The Hotel side (deservedly) won after a number (I lost count) of penalties. I would like to highlight the independence of the referee, Matthias Ullrich, and the great skill of Andrew Pitman, David Jones, our youngest player, and John Mansfield our brave goalkeeper and the only ‘conference’ player that stayed on the pitch during the entire game – we can not blame him for losing on penalties!
The last day of the conference began with a session on molecular techniques for identification and detection. Charles Manceau, David Stead, Maria Lopez and Norm Schaad showed that molecular methods, in particular different types of PCR, can be successfully used for the detection of bacteria (P. syringae, Ralstonia solanacearum and Acidovorax). Arantxa Rico showed that primers directed to the phaseolotoxin gene cluster should not be used to detect P. syringae pv. phaseolicola because some strains do not produce this toxin. The last two sessions were on new emerging pathogens and taxonomy. David Stead reviewed the new and old plant pathogenic bacteria highlighting pathogens of increasing economic concern and Anne Willems reviewed the taxonomy of phytopathogenic expseudomonads.
The last talk by Laurent Sutra on a potential new P. syringae pathovar that causes bacterial canker of cherry generated heated discussion. Norm Schaad suggested that it would be more appropriate to include these strains in a new species, David Stead liked the idea of a new pathovar and I proposed that if they are only pathogenic on cherry, they should be included in P. syringae pv. morsprunorum regardless of differences observed in some tests and rep-PCR. By this time, we realised that our interpretations of a pathovar is not exactly the same. Do we need a new definition? The discussion on this topic continued during the farewell party and even during a swim after midnight with the moon illuminating the Mediterranean Sea.
I would like to finish by thanking BSPP for their financial contribution that enabled me to attend this conference.
Joana Vicente, Horticulture Research International, Wellesbourne.
