HpaP Sequesters HrpJ, an Essential Component of Ralstonia solanacearum Virulence That Triggers Necrosis in Arabidopsis.

The Gram-negative bacterium Ralstonia solanacearum, the causal agent of bacterial wilt, is a worldwide major crop pathogen whose virulence strongly relies on a type III secretion system (T3SS). This extracellular apparatus allows the translocation of proteins, called type III effectors (T3Es), directly into the host cells. To date, very few data are available in plant-pathogenic bacteria concerning the role played by type III secretion (T3S) regulators at the posttranslational level. We have demonstrated that HpaP, a putative T3S substrate specificity switch protein of R. solanacearum, controls T3E secretion. To better understand the role of HpaP on T3S control, we analyzed the secretomes of the GMI1000 wild-type strain as well as the hpaP mutant using a mass spectrometry experiment (liquid chromatography tandem mass spectrometry). The secretomes of both strains appeared to be very similar and highlighted the modulation of the secretion of few type III substrates. Interestingly, only one type III-associated protein, HrpJ, was identified as specifically secreted by the hpaP mutant. HrpJ appeared to be an essential component of the T3SS, essential for T3S and pathogenicity. We further showed that HrpJ is specifically translocated in planta by the hpaP mutant and that HrpJ can physically interact with HpaP. Moreover, confocal microscopy experiments demonstrated a cytoplasmic localization for HrpJ once in planta. When injected into Arabidopsis thaliana leaves, HrpJ is able to trigger a necrosis on 16 natural accessions. A genome-wide association mapping revealed a major association peak with 12 highly significant single-nucleotide polymorphisms located on a plant acyl-transferase.

An atypical NLR gene confers bacterial wilt susceptibility in Arabidopsis.

Quantitative disease resistance (QDR) remains the most prevalent form of plant resistance in crop fields and wild habitats. Genome-wide association studies (GWAS) have proved to be successful in deciphering the quantitative genetic basis of complex traits such as QDR. To unravel the genetics of QDR to the devastating worldwide bacterial pathogen Ralstonia solanacearum, we performed a GWAS by challenging a highly polymorphic local mapping population of Arabidopsis thaliana with four R. solanacearum type III effector (T3E) mutants, identified as key pathogenicity determinants after a first screen on an A. thaliana core collection of 25 accessions. Although most quantitative trait loci (QTLs) were highly specific to the identity of the T3E mutant (ripAC, ripAG, ripAQ, and ripU), we finely mapped a common QTL located on a cluster of nucleotide-binding domain and leucine-rich repeat (NLR) genes that exhibited structural variation. We functionally validated one of these NLRs as a susceptibility factor in response to R. solanacearum, named it Bacterial Wilt Susceptibility 1 (BWS1), and cloned two alleles that conferred contrasting levels of QDR. Further characterization indicated that expression of BWS1 leads to suppression of immunity triggered by different R. solanacearum effectors. In addition, we showed a direct interaction between BWS1 and RipAC T3E, and BWS1 and SUPPRESSOR OF G2 ALLELE OF skp1 (SGT1b), the latter interaction being suppressed by RipAC. Together, our results highlight a putative role for BWS1 as a quantitative susceptibility factor directly targeted by the T3E RipAC, mediating negative regulation of the SGT1-dependent immune response.

Study of natural diversity in response to a key pathogenicity regulator of Ralstonia solanacearum reveals new susceptibility genes in Arabidopsis thaliana.

Ralstonia solanacearum gram-negative phytopathogenic bacterium exerts its virulence through a type III secretion system (T3SS) that translocates type III effectors (T3Es) directly into the host cells. T3E secretion is finely controlled at the posttranslational level by helper proteins, T3SS control proteins, and type III chaperones. The HpaP protein, one of the type III secretion substrate specificity switch (T3S4) proteins, was previously highlighted as a virulence factor on Arabidopsis thaliana Col-0 accession. In this study, we set up a genome-wide association analysis to explore the natural diversity of response to the hpaP mutant of two A. thaliana mapping populations: a worldwide collection and a local population. Quantitative genetic variation revealed different genetic architectures in both mapping populations, with a global delayed response to the hpaP mutant compared to the GMI1000 wild-type strain. We have identified several quantitative trait loci (QTLs) associated with the hpaP mutant inoculation. The genes underlying these QTLs are involved in different and specific biological processes, some of which were demonstrated important for R. solanacearum virulence. We focused our study on four candidate genes, RKL1, IRE3, RACK1B, and PEX3, identified using the worldwide collection, and validated three of them as susceptibility factors. Our findings demonstrate that the study of the natural diversity of plant response to a R. solanacearum mutant in a key regulator of virulence is an original and powerful strategy to identify genes directly or indirectly targeted by the pathogen.

The association between health literacy, social support and self-efficacy in mothers of preterm neonates.

BACKGROUND: Health literacy, social support and self-efficacy are important concepts in mothers of preterm neonates. The purpose of study was to determine the association between health literacy, social support and self-efficacy of mothers of preterm neonates admitted to the neonatal intensive care unit. METHODS: This descriptive correlational study was conducted from November 2017 to January 2019 on 200 mothers of preterm neonates admitted to the neonatal intensive care unit of selected hospitals affiliated with Iran University of Medical Sciences, Tehran, Iran. Data were collected using demographic, maternal health literacy, maternal self-efficacy and multidimensional scale of perceived social support questionnaires. Data were analyzed by descriptive statistics (mean and standard deviation) and inferential tests (Pearson correlation coefficient) using SPSS-PC (v.23) and R software. RESULTS: The data showed 23.5% of mothers had high likelihood of low health literacy, 45.5% had possibility of low health literacy and 31% had adequate with mean score 2.57 ± 1.28. Also, 9.5% of participants had low perceived social support, 62.5% moderate perceived social support and 28% high perceived social support. Maternal self-efficacy score was 52.54 ± 8.06. Pearson's correlation coefficient analyses revealed a statistically significant positive correlation between maternal health literacy and social support (r = 0.304, p < .001). Also maternal health literacy was positively correlated with the self-efficacy (r = 0.292, p < .001) and self-efficacy was positively correlated with social support (r = 0.440, p < .001). CONCLUSION: Health literacy, social support and self-efficacy of mothers of preterm neonates admitted to the neonatal intensive care unit in Iran are related together. Therefore, neonatal care nurses need to note this in care of this clients and adopt strategies to enhance them.

Iranian healthcare professionals' perspectives about factors influencing the use of telemedicine in diabetes management.

AIM: To identify factors influencing the use of telemedicine in diabetes management from the perspectives of healthcare professionals. METHODS: This was a quantitative study that was conducted in 2016. The participants were 240 nurses and 55 physicians from three teaching hospitals as well as from one endocrinology and metabolism research center. No sampling method was used and the data were collected by using a five-point (1 to 5) Likert scale questionnaire, which had 37 questions. Descriptive and inferential statistics (Mann-Whitney U test) were used to analyze the data. RESULTS: The findings showed that both physicians (4.06 ± 0.69) and nurses (4.02 ± 0.61) tended to use telemedicine technology for managing diabetes. Overall, the lowest mean value for physicians (3.79 ± 0.82) was related to the compatibility of telemedicine with other clinical activities in diabetes management. For nurses, the lowest mean value pertained to the usefulness of telemedicine in diabetes management (3.99 ± 0.53) and their attitude toward using this technology (3.99 ±0.65). CONCLUSION: Although physicians and nurses agreed on using telemedicine technology in diabetes management, it is necessary to consider their concerns prior to the implementation and deployment of new technologies. This approach will help to improve the level of technology acceptance among the users.