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The apoplast is the arena in which endophytic pathogens such as Pseudomonas syringae grow and interact with plant cells. Using metabolomic and ion analysis techniques, this study shows how the composition of Phaseolus vulgaris leaf apoplastic fluid changes during the first six hours of compatible and incompatible interactions with two strains of P. syringae pv. phaseolicola ( Pph) that differ in the presence of the genomic island PPHGI-1. Leaf inoculation with the avirulent island-carrying strain Pph 1302A elicited effector-triggered immunity (ETI) and resulted in specific changes in apoplast composition, including increases in conductivity, pH, citrate, γ-aminobutyrate (GABA) and K+, that are linked to the onset of plant defence responses. Other apoplastic changes, including increases in Ca2+, Fe2/3+ Mg2+, sucrose, β-cyanoalanine and several amino acids, occurred to a relatively similar extent in interactions with both Pph 1302A and the virulent, island-less strain Pph RJ3. Metabolic footprinting experiments established that Pph preferentially metabolizes malate, glucose and glutamate, but excludes certain other abundant apoplastic metabolites, including citrate and GABA, until preferred metabolites are depleted. These results demonstrate that Pph is well-adapted to the leaf apoplast metabolic environment and that loss of PPHGI-1 enables Pph to avoid changes in apoplast composition linked to plant defences. [ABSTRACT FROM AUTHOR]

Asperger's Syndrome (AS) is an autistic spectrumdisorder characterised by normal to high IQ but with marked impairment insocial skills. Successful social skills training appears to be best achievedeither in situ or in role-play situations where users can explore differentoutcomes resulting from their social behaviour. Single user virtual environments(SVEs) provide an opportunity for users with AS to learn social interactionskills in a safe environment which they can visit as many times as they like.Theuse of game-like tasks can provide an incentive and can also be used to guidethe user through progressive learning stages. Collaborative virtual environments(CVEs) allow several users to interact simultaneously within the virtual environment,each taking different perspectives or role-play characters. Within the ASinteractive project a series of SVEs and CVEs have been developed in collaborationwith users and professional groups with an overall aim of supporting socialskills learning. Initial evaluation studies have been carried out which havebeen used to both inform and refine the design of these virtual environments(VEs) as well as giving an insight into the understanding and interpretationof these technologies by users with AS. [ABSTRACT FROM AUTHOR]

Bacterial canker is a major disease of stone fruits and is a critical limiting factor to sweet cherry ( Prunus avium ) production worldwide. One important strategy for disease control is the development of resistant varieties. Partial varietal resistance in sweet cherry is discernible using shoot or whole tree inoculations; however, these quantitative differences in resistance are not evident in detached leaf assays. To identify novel sources of resistance to canker, we used a rapid leaf pathogenicity test to screen a range of wild cherry, ornamental Prunus species and sweet cherry × ornamental cherry hybrids with the canker pathogens, Pseudomonas syringae pvs syringae , morsprunorum races 1 and 2, and avii . Several Prunus accessions exhibited limited symptom development following inoculation with each of the pathogens, and this resistance extended to 16 P . syringae strains pathogenic on sweet cherry and plum. Resistance was associated with reduced bacterial multiplication after inoculation, a phenotype similar to that of commercial sweet cherry towards nonhost strains of P . syringae . Progeny resulting from a cross of a resistant ornamental species Prunus incisa with susceptible sweet cherry ( P . avium ) exhibited resistance indicating it is an inherited trait. Identification of accessions with resistance to the major bacterial canker pathogens is the first step towards characterizing the underlying genetic mechanisms of resistance and introducing these traits into commercial germplasm., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Plant Pathology published by John Wiley & Sons Ltd on behalf of British Society for Plant Pathology.)

The co-evolution of bacterial plant pathogens and their hosts is a complex and dynamic process. Host resistance imposes stress on invading pathogens that can lead to changes in the bacterial genome enabling the pathogen to escape host resistance. We have observed this phenomenon with the plant pathogen Pseudomonas syringae pv. phaseolicola where isolates that have lost the genomic island PPHGI-1 carrying the effector gene avrPphB from its chromosome are infective against previously resistant plant hosts. However, we have never observed island extinction from the pathogen population within a host suggesting the island is maintained. Here, we present a mathematical model which predicts different possible fates for the island in the population; one outcome indicated that PPHGI-1 would be maintained at low frequency in the population long term, if it confers a fitness benefit. We empirically tested this prediction and determined that PPHGI-1 frequency in the bacterial population drops to a low but consistently detectable level during host resistance. Once PPHGI-1-carrying cells encounter a susceptible host, they rapidly increase in the population in a negative frequency-dependent manner. Importantly, our data show that mobile genetic elements can persist within the bacterial population and increase in frequency under favourable conditions., (© 2016 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)