Re-programming of Pseudomonas syringae pv. actinidiae gene expression during early stages of infection of kiwifruit

Abstract

BackgroundPseudomonas syringae is a widespread bacterial species complex that includes a number of significant plant pathogens. Amongst these, P. syringae pv. actinidiae (Psa) initiated a worldwide pandemic in 2008 on cultivars of Actinidia chinensis var. chinensis. To gain information about the expression of genes involved in pathogenicity we have carried out transcriptome analysis of Psa during the early stages of kiwifruit infection.ResultsGene expression in Psa was investigated during the first five days after infection of kiwifruit plantlets, using RNA-seq. Principal component and heatmap analyses showed distinct phases of gene expression during the time course of infection. The first phase was an immediate transient peak of induction around three hours post inoculation (HPI) that included genes that code for a Type VI Secretion System and nutrient acquisition (particularly phosphate). This was followed by a significant commitment, between 3 and 24 HPI, to the induction of genes encoding the Type III Secretion System (T3SS) and Type III Secreted Effectors (T3SE). Expression of these genes collectively accounted for 6.3% of the bacterial transcriptome at this stage. There was considerable variation in the expression levels of individual T3SEs but all followed the same temporal expression pattern, with the exception of hopAS1, which peaked later in expression at 48 HPI. As infection progressed over the time course of five days, there was an increase in the expression of genes with roles in sugar, amino acid and sulfur transport and the production of alginate and colanic acid. These are both polymers that are major constituents of extracellular polysaccharide substances (EPS) and are involved in biofilm production. Reverse transcription-quantitative PCR (RT-qPCR) on an independent infection time course experiment showed that the expression profile of selected bacterial genes at each infection phase correlated well with the RNA-seq data.ConclusionsThe results from this study indicate that there is a complex remodeling of the transcriptome during the early stages of infection, with at least three distinct phases of coordinated gene expression. These include genes induced during the immediate contact with the host, those involved in the initiation of infection, and finally those responsible for nutrient acquisition.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5197-5) contains supplementary material, which is available to authorized users.

Early Pathogen Recognition and Antioxidant System Activation Contributes to Actinidia arguta Tolerance Against Pseudomonas syringae Pathovars actinidiae and actinidifoliorum

“…Together, these results confirm the higher susceptibility of A. chinensis probably because bacteria are able to easily progress and reproduce inside its vascular system, whereas in A. arguta bacterial movement and reproduction is more restricted (Wang et al, 2017). It is interesting to note that in the present work foliar symptoms began to appear as soon 1 dpi, whereas in other studies symptoms only appear after the first 5 dpi (McAtee et al, 2018). We hypothesize that the inoculation method selected in the current work (i.e.…”

AvrE1 and HopR1 from Pseudomonas syringae pv. actinidiae are additively required for full virulence on kiwifruit

“…Alternatively, T3S helper hrpW1 , which was not included in the original screen, may be involved in conferring full virulence. This gene is expressed at high levels during in planta infection of Psa3 compared to other functionally redundant helpers (Figure ) (Kvitko et al ., 2007; McAtee et al ., 2018). To assess this, genomic knockin constructs of hrpW1 , hopM1 (with chaperone shcM ), or avrE1 (with chaperone shcE ) were generated with their native HrpL box promoters and reintegrated into Psa3 V13 genome at the CEL knockout site (Figure 3a).…”

Blue‐light perception by epiphytic Pseudomonas syringae drives chemoreceptor expression, enabling efficient plant infection

“…PsPto is a weak epiphytic bacterium and therefore the efficiency to deal with the phyllosphere environment would determine the output of the infection. Our analyses contemplate conditions that have not been previously included in other transcriptomic studies on epiphytic populations (Yu et al ., 2013; McAtee et al ., 2018; Nobori et al ., 2018; Helmann et al ., 2019). We determined the alterations in transcripts levels at short times and under different light conditions.…”

“…Bacterial determinants that affect virulence have been extensively studied in phytopathogenic Pseudomonas (Xin and He, 2013;Dudnik and Dudler, 2014;Ichinose et al, 2016;Xin et al, 2018;An et al, 2020). However, only a limited number of reports explore, from a global perspective, the bacterial traits required for leaf colonization in the epiphytic stage (Yu et al, 2013;McAtee et al, 2018;Nobori et al, 2018;Helmann et al, 2019). Environmental conditions at the time of bacterial contact with the leaf surface may influence colonization success.…”

“…Our analyses contemplate conditions that have not been previously included in other transcriptomic studies on epiphytic populations (Yu et al, 2013;McAtee et al, 2018;Nobori et al, 2018;Helmann et al, 2019). We determined the alterations in transcripts levels at short times and under different light conditions.…”