Pathways of flower infection and pollen-mediated dispersion of Pseudomonas syringae pv. actinidiae, the causal agent of kiwifruit bacterial canker

Flowers can provide a protected and nutrient-rich environment to the epiphytic microflora,thus representing a sensible entry point for pathogens such as Pseudomonas syringae pv.actinidiae(Psa).This bacterium can colonize both male and female Actinidia flowers,causing flower browning and fall,and systemic invasion of the host plant,eventually leading to its death.However,the process of flower colonization and penetration into the host tissues has not yet been fully elucidated.In addition,the presence of Psa in the pollen from infected flowers,and the role of pollination in the spread of Psa requires confirmation.The present study employed a Psa strain constitutively expressing the fluorescent GFPuv protein,to visualize in vivo flower colonization.Microscopy observations were performed by means of confocal laser scanning and wide-field fluorescent microscopy,and were coupled with the study of Psa population dynamics by quantitative PCR(q-PCR).The pathogen was shown to colonize stigmata,move along the stylar furrow,and penetrate the receptacles via the style or nectarhodes.Once the receptacle was invaded,the pathogen migrated along the flower pedicel and became systemic.Psa was also able to colonize the anthers epiphytically and endophytically.Infected male flowers produced contaminated pollen,which could transmit Psa to healthy plants.Finally,pollinators(Apis mellifera and Bombus terrestris)were studied in natural conditions,showing that,although they can be contaminated with Psa,the pathogen’s transmission via pollinators is contrasted by its short survival in the hive.

Knockdown of MLO genes reduces susceptibility to powdery mildew in grapevine

Erysiphe necator is the causal agent of powdery mildew(PM),one of the most destructive diseases of grapevine.PM is controlled by sulfur-based and synthetic fungicides,which every year are dispersed into the environment.This is why PM-resistant varieties should become a priority for sustainable grapevine and wine production.PM resistance can be achieved in other crops by knocking out susceptibility S-genes,such as those residing at genetic loci known as MLO(Mildew Locus O).All MLO S-genes of dicots belong to the phylogenetic clade V,including grapevine genes VvMLO7,11 and 13,which are upregulated during PM infection,and VvMLO6,which is not upregulated.Before adopting a gene-editing approach to knockout candidate S-genes,the evidence that loss of function of MLO genes can reduce PM susceptibility is necessary.This paper reports the knockdown through RNA interference of VvMLO6,7,11 and 13.The knockdown of VvMLO6,11 and 13 did not decrease PM severity,whereas the knockdown of VvMLO7 in combination with VvMLO6 and VvMLO11 reduced PM severity up to 77%.The knockdown of VvMLO7 and VvMLO6 seemed to be important for PM resistance,whereas a role for VvMLO11 does not seem likely.Cell wall appositions(papillae)were present in both resistant and susceptible lines in response to PM attack.Thirteen genes involved in defense were less upregulated in infected mlo plants,highlighting the early mlo-dependent disruption of PM invasion.

腺苷相关基因变异在原发性高血压易感性中的作用

Objective: To test markers within adenosine-related genes: A1 and A2a recepto rs(ADORA1, ADORA2a) and adenosine deaminase(ADA) for potential involvement in es sential hypertension (EH). Design: Case-control association study investigating gene variants for the ADORA1, ADORA2a and ADA genes. Participants: The study us ed a cohort of 249 unrelated hypertensive individuals who were diagnosed with hy pertension, and an age, sex and ethnically matched group of 249 normotensive con trols. Results: The association analysis indicated that both allele and genotype frequencies did not differ significantly between the case and control groups (P >0.05) for any of the markers tested. Conclusion: The adenosine-related gene v ariants do not appear to alter susceptibility to the disease in this group of es sential hypertensives. However, involvement of these genes and the adenosine sys tem cannot be conclusively excluded from essential hypertension pathogenesis as other gene variants may still be involved.

Comparative Genomic Study Reveals a Transition from TA Richness in Invertebrates to GC Richness in Vertebrates at CpG Flank-ing Sites:An Indication for Context-Dependent Mutagenicity of Methylated CpG Sites

Vertebrate genomes are characterized with CpG deficiency, particularly for GCpoor regions. The GC content-related CpG deficiency is probably caused by context-dependent deamination of methylated CpG sites. This hypothesis was examined in this study by comparing nucleotide frequencies at CpG flanking positions among invertebrate and vertebrate genomes. The finding is a transition of nucleotide preference of 5＇ T to 5＇ A at the invertebrate-vertebrate boundary, indicating that a large number of CpG sites with 5＇ Ts were depleted because of global DNA methylation developed in vertebrates. At genome level, we investigated CpG observed/expected （obs/exp） values in 500 bp fragments, and found that higher CpG obs/exp value is shown in GC-poor regions of invertebrate genomes （except sea urchin） but in GC-rich sequences of vertebrate genomes. We next compared GC content at CpG flanking positions with genomic average, showing that the GC content is lower than the average in invertebrate genomes, but higher than that in vertebrate genomes. These results indicate that although 5＇ T and 5＇ A are different in inducing deamination of methylated CpG sites, GC content is even more important in affecting the deamination rate. In all the tests, the results of sea urchin are similar to vertebrates perhaps due to its fractional DNA methylation. CpG deficiency is therefore suggested to be mainly a result of high mutation rates of methylated CpG sites in GC-poor regions.

Variation in decomposition stages and carrion insect succession in a dry tropical climate and its effect on estimating postmortem interval

Insects have an important role in minimum postmortem interval(PMImin)estimation.An accurate PMImin estimation relies on a comprehensive study of the development and succes-sion of local carrion insects.No published research on carrion insect succession exists for tropical north Queensland.To address this,we aimed to obtain preliminary observational data concerning the rate of decomposition and insect succession on pig carcasses in Townsville and compare these with other regions of Australia and overseas.Adult insects were collected daily from three pig carcasses for 30d during summer and identified to fa-mily level.Observations of decomposition rate were made each day and progression through the stages of decomposition were recorded.Adult insects were identified to family and their presence/absence used as a proxy for arrival at/departure from the remains,respectively.These preliminary data highlight several interesting trends that may be inform-ative for forensic PMImin estimation.Decomposition was rapid:all carcasses were at the dry/remains stage by Day 5,which was substantially quicker than all other regions in the com-parison.Differences were also observed in the presence/absence of insect families and their arrival and departure times.Given the rapid progression through early decomposition,we argue that later-arriving coleopteran taxa may be more forensically informative in tropical Australia,in contrast with temperate regions where Diptera appear most useful.This research contributes preliminary observational data to understanding insect succession pat-terns in tropical Australia and demonstrates the critical need for comprehensive local succes-sion data for each climatic region of Australia to enable accurate PMImin estimation.These data will inform future research targeted at gaining a more comprehensive understanding of insect succession in the Australian tropics.