First report of black leaf streak disease in bananas caused by Pseudocercospora fijiensis on Mauritius island.

Pseudocercospora fijiensis, the causal agent of the black leaf streak disease of bananas (plants in the genus Musa) (BLSD), is considered to be the major economic threat to export-banana cultivation (de Bellaire, Fouré, Abadie, & Carlier, 2010). The disease has a worldwide distribution throughout the humid tropical regions and has been previously reported in the Southwestndian Ocean (SWIO) area: in 1993 in Mayotte and Comoros islands (DR Jones & Mourichon, 1993), in 2000 in Madagascar (Jones, 2003; Rivas, Zapater, Abadie, & Carlier, 2004) and in 2018 in Reunion Island (Rieux et al., 2019). In Mauritius, the presence of Pseudocercospora fijiensis was suspected in 1996 (Soomary & Benimadhu, 1998) but has never been confirmed, as symptoms could have been confounded with Pseudocercospora musae or Pseudocercospora eumusae, two causal agents of others leaf spot diseases of banana which were previously described in Mauritius in 1959 (Orieux & Felix, 1968) and 2000 (Carlier, Zapater, Lapeyre, Jones, & Mourichon, 2000), respectively. In March 2022, typical BLSD symptoms were observed at relatively low prevalence in a Cavendish crop located in the "Balance John" area (site S1 on Fig. S1-A) of Mauritius island. Typical early symptoms (stages 2) were 1- to 4-mm long brown streaks at the abaxial leaf surface, and typical older streaks (stages 3 and 4) were also observed (Fig. S1-B). These symptoms were mixed with symptoms of ELSD caused by P. eumusae. Since both species cannot be clearly distinguished only on the description of symptoms, conidial sporulation on stages 2 was checked in the laboratory (Ngando et al., 2015) since P. eumusae does not produce conidia on these young stages. In April 2022, banana leaves bearing symptoms of leaf spot diseases were collected in 7 different sites (Fig. S1-A). All leaf fragments were sent to the CIRAD laboratories where molecular diagnosis was performed following the protocol developed by Arzanlou et al. (2007). In brief, genomic DNA was extracted from ground leaf fragments displaying symptoms using the DNeasy® Plant Mini Kit (Qiagen®, Courtaboeuf, France). At each site, a total of 6 lesions cut from 6 different leaves were pooled. The DNA extracts were added as templates for real-time PCR assay designed to specifically detect the presence of P. fijiensis, P. musae and P. eumusae using MFbf/MFbrtaq/MFbp, MEbf/MEbrtaq/FMep and MMbf/Mmbrtaq/FMep primers and probes, respectively (Arzanlou et al., 2007). Both positive and negative controls were included in the assay and every sample reaction was duplicated. P. fijiensis was detected from 2 out of 7 sites (S2 and S7, see Fig.S2-B). P. eumusae was detected at all sites while P. musae was found in one site only (S6). Interestingly, our results also showed coinfection by P. fijiensis - P. eumusae & P. musae - P. eumusae on several sites. The presence of P. fijiensis was further confirmed by several investigations performed on conidia isolated from S2 samples including i) morphological observations of conidia displaying P. fijiensis type description (Pérez-Vicente, Carreel, Roussel, Carlier, & Abadie (2021), Fig. S2-A), ii) DNA sequencing of 16S ribosomal gene with ITS1 & ITS4 primers (GenBank accessions Nos. OR515818-OR515810) with BLAST results displaying percentages of identity > 99.70% with type strains and iii) Koch's postulates were fulfilled by artificial inoculation of detached leaf pieces as described in Pérez-Vicente, Carreel, Roussel, Carlier, & Abadie (2021) (Fig. S2-D). In brief, for the artificial inoculation, symptoms obtained after inoculation of both a strain isolated in Mauritius (S2-MAU) and a positive control (T+) were compared and shown to be typical of P. fijiensis species for the 3 replicates. To the best of our knowledge, this is the first official report of P. fijiensis and BLSD in Mauritius Island. This revelation holds significant importance for both the agricultural and scientific communities, shedding light on the potential spread and impact of this devastating pathogen in previously unaffected regions. From a global perspective, this discovery underscores the interconnectedness of agricultural ecosystems and the need for vigilance in monitoring and responding to emerging plant diseases in an increasingly interconnected world (Vega et al. 2022). Future investigations will be required to monitor the spread of BLSD on the island, describe the genetic structure of populations and identify routes of invasion at the SWOI scale.

Complex adaptive architecture underlies adaptation to quantitative host resistance in a fungal plant pathogen.

Plant pathogens often adapt to plant genetic resistance so characterization of the architecture underlying such an adaptation is required to understand the adaptive potential of pathogen populations. Erosion of banana quantitative resistance to a major leaf disease caused by polygenic adaptation of the causal agent, the fungus Pseudocercospora fijiensis, was recently identified in the northern Caribbean region. Genome scan and quantitative genetics approaches were combined to investigate the adaptive architecture underlying this adaptation. Thirty-two genomic regions showing host selection footprints were identified by pool sequencing of isolates collected from seven plantation pairs of two cultivars with different levels of quantitative resistance. Individual sequencing and phenotyping of isolates from one pair revealed significant and variable levels of correlation between haplotypes in 17 of these regions with a quantitative trait of pathogenicity (the diseased leaf area). The multilocus pattern of haplotypes detected in the 17 regions was found to be highly variable across all the population pairs studied. These results suggest complex adaptive architecture underlying plant pathogen adaptation to quantitative resistance with a polygenic basis, redundancy, and a low level of parallel evolution between pathogen populations. Candidate genes involved in quantitative pathogenicity and host adaptation of P. fijiensis were identified in genomic regions by combining annotation analysis with available biological data.

Convergent Adaptation to Quantitative Host Resistance in a Major Plant Pathogen.

Plant pathogens can adapt to quantitative resistance, eroding its effectiveness. The aim of this work was to reveal the genomic basis of adaptation to such a resistance in populations of the fungus Pseudocercospora fijiensis, a major devastating pathogen of banana, by studying convergent adaptation on different cultivars. Samples from P. fijiensis populations showing a local adaptation pattern on new banana hybrids with quantitative resistance were compared, based on a genome scan approach, with samples from traditional and more susceptible cultivars in Cuba and the Dominican Republic. Whole-genome sequencing of pools of P. fijiensis isolates (pool-seq) sampled from three locations per country was conducted according to a paired population design. The findings of different combined analyses highly supported the existence of convergent adaptation on the study cultivars between locations within but not between countries. Five to six genomic regions involved in this adaptation were detected in each country. An annotation analysis and available biological data supported the hypothesis that some genes within the detected genomic regions may play a role in quantitative pathogenicity, including gene regulation. The results suggested that the genetic basis of fungal adaptation to quantitative plant resistance is at least oligogenic, while highlighting the existence of specific host-pathogen interactions for this kind of resistance.IMPORTANCE Understanding the genetic basis of pathogen adaptation to quantitative resistance in plants has a key role to play in establishing durable strategies for resistance deployment. In this context, a population genomic approach was developed for a major plant pathogen (the fungus Pseudocercospora fijiensis causing black leaf streak disease of banana) whereby samples from new resistant banana hybrids were compared with samples from more susceptible conventional cultivars in two countries. A total of 11 genomic regions for which there was strong evidence of selection by quantitative resistance were detected. An annotation analysis and available biological data supported the hypothesis that some of the genes within these regions may play a role in quantitative pathogenicity. These results suggested a polygenic basis of quantitative pathogenicity in this fungal pathogen and complex molecular plant-pathogen interactions in quantitative disease development involving several genes on both sides.

Central American and Caribbean population history of the Pseudocercospora fijiensis fungus responsible for the latest worldwide pandemics on banana.

Among the emerging fungal diseases threatening food security, the Pseudocercospora fijiensis fungus causing black leaf streak disease of banana is one of the most marked examples of a recent worldwide pandemic on a major crop. We assessed how this pathogen spread throughout the latest invaded region, i.e. Central America and the Caribbean. We retraced its population history combining detailed monitoring information on disease outbreaks and population genetic analyses based on large-scale sampling of P. fijiensis isolates from 121 locations throughout the region. The results first suggested that sexual reproduction was not lost during the P. fijiensis expansion, even in the insular Caribbean context, and a high level of genotypic diversity was maintained in all the populations studied. The population genetic structure of P. fijiensis and historical data showed that two disease waves swept northward and southward in all banana-producing countries in the study area from an initial entry point in Honduras, probably mainly through gradual stepwise spore dispersal. Serial founder events accompanying the northern and southern waves led to the establishment of two different genetic groups. A different population structure was detected on the latest invaded islands (Martinique, Dominica and Guadeloupe), revealing multiple introductions and admixture events that may have been partly due to human activities. The results of this study highlight the need to step up surveillance to limit the spread of other known emerging diseases of banana spread mainly by humans, but also to curb gene flow between established pathogen populations which could increase their evolutionary potential.

Pattern of local adaptation to quantitative host resistance in a major pathogen of a perennial crop.

Understanding the mechanisms involved in pathogen adaptation to quantitative resistance in plants has a key role to play in establishing durable strategies for resistance deployment, especially in perennial crops. The erosion of quantitative resistance has been recently suspected in Cuba and the Dominican Republic for a major fungal pathogen of such a crop: Pseudocercospora fijiensis, causing black leaf streak disease on banana. This study set out to test whether such erosion has resulted from an adaptation of P. fijiensis populations, and to determine whether or not the adaptation is local. Almost 600 P. fijiensis isolates from Cuba and the Dominican Republic were sampled using a paired-population sampling design on resistant and susceptible banana varieties. A low genetic structure of the P. fijiensis populations was detected in each country using 16 microsatellite markers. Cross-inoculation experiments using isolates from susceptible and resistant cultivars were carried out, measuring a quantitative trait (the diseased leaf area) related to pathogen fitness on three varieties. A further analysis based on those data suggested the existence of a local pattern of adaptation to resistant cultivars in both of the study countries, due to the existence of specific (or genotype by genotype) host-pathogen interactions. However, neither cost nor benefit effects for adapted populations were found on the widely used "Cavendish" banana group. These results highlight the need to study specific host-pathogen interactions and pathogen adaptation on a wide range of quantitative resistance phenotypes in banana, in order to develop durable strategies for resistance deployment.

Specific Targeting of Plant and Apicomplexa Parasite Tubulin through Differential Screening Using In Silico and Assay-Based Approaches.

Dinitroanilines are chemical compounds with high selectivity for plant cell α-tubulin in which they promote microtubule depolymerization. They target α-tubulin regions that have diverged over evolution and show no effect on non-photosynthetic eukaryotes. Hence, they have been used as herbicides over decades. Interestingly, dinitroanilines proved active on microtubules of eukaryotes deriving from photosynthetic ancestors such as Toxoplasma gondii and Plasmodium falciparum, which are responsible for toxoplasmosis and malaria, respectively. By combining differential in silico screening of virtual chemical libraries on Arabidopsis thaliana and mammal tubulin structural models together with cell-based screening of chemical libraries, we have identified dinitroaniline related and non-related compounds. They inhibit plant, but not mammalian tubulin assembly in vitro, and accordingly arrest A. thaliana development. In addition, these compounds exhibit a moderate cytotoxic activity towards T. gondii and P. falciparum. These results highlight the potential of novel herbicidal scaffolds in the design of urgently needed anti-parasitic drugs.

Activation of the G protein-coupled estrogen receptor, but not estrogen receptor α or ß, rapidly enhances social learning.

Social learning is a highly adaptive process by which an animal acquires information from a conspecific. While estrogens are known to modulate learning and memory, much of this research focuses on individual learning. Estrogens have been shown to enhance social learning on a long-term time scale, likely via genomic mechanisms. Estrogens have also been shown to affect individual learning on a rapid time scale through cell-signaling cascades, rather than via genomic effects, suggesting they may also rapidly influence social learning. We therefore investigated the effects of 17ß-estradiol and involvement of the estrogen receptors (ERs) using the ERα agonist propyl pyrazole triol, the ERß agonist diarylpropionitrile, and the G protein-coupled ER 1 (GPER1) agonist G1 on the social transmission of food preferences (STFP) task, within a time scale that focused on the rapid effects of estrogens. General ER activation with 17ß-estradiol resulted in a modest facilitation of social learning, with mice showing a preference up to 30min of testing. Specific activation of the GPER1 also rapidly enhanced social learning, with mice showing a socially learned preference up to 2h of testing. ERα activation instead shortened the expression of a socially learned food preference, while ERß activation had little to no effects. Thus, rapid estrogenic modulation of social learning in the STFP may be the outcome of competing action at the three main receptors. Hence, estrogens' rapid effects on social learning likely depend on the specific ERs present in brain regions recruited during social learning.

SERCA2a gene therapy can improve symptomatic heart failure in δ-sarcoglycan-deficient animals.

The loss of dystrophin or its associated proteins results in the development of muscle wasting frequently associated with cardiomyopathy. Contractile cardiac tissue is injured and replaced by fibrous tissue or fatty infiltrates, leading to a progressive decrease of the contractile force and finally to end-stage heart failure. At the time symptoms appear, restoration of a functional allele of the causative gene might not be sufficient to prevent disease progression. Alterations in Ca(2+) transport and intracellular calcium levels have been implicated in many types of pathological processes, especially in heart disease. On the basis of a gene transfer strategy, we analyzed the therapeutic efficacy of primary gene correction in a δ-sarcoglycan (δ-SG)-deficient animal model versus gene transfer of the Ca(2+) pump hSERCA2a (human sarco-endoplasmic reticulum calcium ATPase 2a), at a symptomatic stage of heart disease. Our results strongly suggest that restoration of δ-SG at this stage of disease will not lead to improved clinical outcome. However, restoration of proper Ca(2+) handling by means of amplifying SERCA2a expression in the myocardium can lead to functional improvement. Abnormalities in Ca(2+) handling play an important role in disease progression toward heart failure, and increased SERCA2a levels appear to significantly improve cardiac contraction and relaxation. Beneficial effects persist at least over a period of 6 months, and the evolution of cardiac functional parameters paralleled those of normal controls. Furthermore, we demonstrate that a plasmid formulation based on amphiphilic block copolymers can provide a safe and efficient platform for myocardial gene therapies. The use of synthetic formulations for myocardial gene transfer might thus overcome one of the major hurdles linked to viral vectors, that is, repeat administrations.

A framework to predict the impacts of shale gas infrastructures on the forest fragmentation of an agroforest region.

We propose a framework to facilitate the evaluation of the impacts of shale gas infrastructures (well pads, roads, and pipelines) on land cover features, especially with regards to forest fragmentation. We used a geographic information system and realistic development scenarios largely inspired by the PA (United States) experience, but adapted to a region of QC (Canada) with an already fragmented forest cover and a high gas potential. The scenario with the greatest impact results from development limited by regulatory constraints only, with no access to private roads for connecting well pads to the public road network. The scenario with the lowest impact additionally integrates ecological constraints (deer yards, maple woodlots, and wetlands). Overall the differences between these two scenarios are relatively minor, with <1 % of the forest cover lost in each case. However, large areas of core forests would be lost in both scenarios and the number of forest patches would increase by 13-21 % due to fragmentation. The pipeline network would have a much greater footprint on the land cover than access roads. Using data acquired since the beginning of the shale gas industry, we show that it is possible, within a reasonable time frame, to produce a robust assessment of the impacts of shale gas extraction. The framework we propose could easily be applied to other contexts or jurisdictions.

CSF N-glycan profiles to investigate biomarkers in brain developmental disorders: application to leukodystrophies related to eIF2B mutations.

BACKGROUND: Primary or secondary abnormalities of glycosylation have been reported in various brain diseases. Decreased asialotransferrin to sialotransferrin ratio in cerebrospinal fluid (CSF) is a diagnostic marker of leukodystrophies related to mutations of genes encoding translation initiation factor, EIF2B. We investigated the CSF glycome of eIF2B-mutated patients and age-matched normal individuals in order to further characterize the glycosylation defect for possible use as a biomarker. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a differential N-glycan analysis using MALDI-TOF/MS of permethylated N-glycans in CSF and plasma of controls and eIF2B-mutated patients. We found in control CSF that tri-antennary/bisecting and high mannose structures were highly represented in samples obtained between 1 to 5 years of age, whereas fucosylated, sialylated structures were predominant at later age. In CSF, but not in plasma, of eIF2B-mutated patient samples, we found increased relative intensity of bi-antennary structures and decreased tri-antennary/bisecting structures in N-glycan profiles. Four of these structures appeared to be biomarker candidates of glycomic profiles of eIF2B-related disorders. CONCLUSION: Our results suggest a dynamic development of normal CSF N-glycan profiles from high mannose type structures to complex sialylated structures that could be correlated with postnatal brain maturation. CSF N-glycome analysis shows relevant quantitative changes associated with eIF2B related disorders. This approach could be applied to other neurological disorders involving developmental gliogenesis/synaptogenesis abnormalities.

Characterization of a cassiicolin-encoding gene from Corynespora cassiicola, pathogen of rubber tree (Hevea brasiliensis).

Corynespora Leaf Fall (CLF) is a major disease of rubber tree (Hevea brasiliensis) caused by the Ascomycota Corynespora cassiicola. Here we describe the cloning and characterization of a gene encoding cassiicolin (Cas), a glycosylated cystein-rich small secreted protein (SSP) identified as a potential CLF disease effector in rubber tree. Three isolates with contrasted levels of aggressiveness were analyzed comparatively. The cassiicolin gene was detected - and the toxin successfully purified - from the isolates with high and medium aggressiveness (CCP and CCAM3 respectively) but not from the isolate with the lowest aggressiveness (CCAM1), suggesting the existence of a different disease effector in the later. CCP and CCAM3 carried strictly identical cassiicolin genes and produced toxins of identical mass, as evidence by mass spectrometry analysis, thus suggesting conserved post-translational modifications in addition to sequence identity. The differences in aggressiveness between CCP and CCAM3 may be attributed to differences in cassiicolin transcript levels rather than qualitative variations in cassiicolin structure. Cassiicolin may play an important role in the early phase of infection since a peak of cassiicolin transcripts occurred in 1 or 2 days after inoculation (before the occurrence of the first symptoms), in both the tolerant and the susceptible cultivars.