Biochemical and molecular identification of a native Bacillus thuringiensis gv. cytolyticus isolate with insecticidal effect against the pod borer larvae (Helicoverpa armigera)

Bouslama, T., Laarif, A., Chattaoui, M., Vial, L., Lavire, C., and Doré, J., and Rhouma, A. 2023. Biochemical and molecular identification of a native Bacillus thuringiensis gv. cytolyticus isolate with insecticidal effect against the pod borer larvae (Helicoverpa armigera). Tunisian Journal of Plant Protection 18 (2): 71-91

A fungal conserved gene from the basidiomycete Hebeloma cylindrosporum is essential for efficient ectomycorrhiza formation

International audienceWe used Agrobacterium-mediate insertional mutagenesis to identify genes in the ectomycorrhizal fungus Hebeloma cylindrosporum that are essential for efficient mycorrhiza formation. One of the mutants presented a dramatically reduced ability to form ectomycorrhizas when grown in the presence of Pinus pinaster. It failed to form mycorrhizas in the presence of 0.5 g l-1 glucose, a condition favourable for mycorrhiza formation by the wild-type strain. It however formed few mycorrhizas when glucose was replaced by fructose or when glucose concentration was increased to 1 g l-1. Scanning electron microscopy examination of these mycorrhizas revealed that this mutant was unable to differentiate true fungal sheath and Hartig net. Molecular analyses showed that the single-copy disrupting T-DNA was integrated 6884 bp downstream the start codon, of an ORF potentially encoding a 3096 amino acid-long protein. This gene, which we named HcMycE1 has orthologs in numerous fungi as well as different other eukaryotic microorganisms. RNAi inactivation of HcMycE1 in wild-type strain also led to a mycorrhizal defect, demonstrating that the non-mycorrhizal phenotype of the mutant was due to mutagenic T-DNA integration in HcMycE1. In the wild-type strain colonizing P. pinaster roots, HcMycE1 was transiently up-regulated before symbiotic structures differentiation. Together with the inability of the mutant to differentiate these structures, this suggests that HcMycE1 plays a crucial role upstream fungal sheath and Hartig net differentiation. This study provides the first characterization of a fungal mutant altered in mycorrhizal ability

Production de plantes androgénétiques de chou à choucroute (Brassica oleracea L. ssp. capitata) par culture d'anthères in vitro

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Import pathways of the mannityl-opines into the bacterial pathogen Agrobacterium tumefaciens: structural, affinity and in vivo approaches

International audienceAgrobacterium tumefaciens pathogens use specific compounds denoted opines as nutrients in their plant tumor niche. These opines are produced by the host plant cells genetically modified by agrobacteria. They are imported into bacteria via solute-binding proteins (SBPs) in association with ABC transporters. The mannityl-opine family encompasses mannopine, mannopinic acid, agropine and agropinic acid. Structural and affinity data on mannopinic acid bound to SBPs are currently lacking while those of the three others mannityl opines are available. We investigated the molecular basis of two pathways for mannopinic acid uptake. MoaA was proposed as the specific SBP for mannopinic acid import in mannityl opines-assimilating agrobacteria, which was validated here using genetic studies and affinity measurements. We structurally characterized the mannopinic acid binding mode of MoaA in two crystal forms at 2.05 and 1.57 Å resolution. We demonstrated that the non-specific SBP MotA, so far characterized as mannopine and Amadori compound importer, was also able to transport mannopinic acid. The structure of MotA bound to mannopinic acid at 2.2 Å resolution defines a different mannopinic acid binding signature, similar to that of mannopine. Combining in vitro and in vivo approaches, this work allowed us to complete the characterization of the mannityl-opines assimilation pathways, highlighting the important role of two dual imports of agropinic and mannopinic acids. Our data shed new light on how the mannityl-opines contribute to the establishment of the ecological niche of agrobacteria from the early to the late stages of tumor development

Anthropization level of Lascaux Cave microbiome shown by regional‐scale comparisons of pristine and anthropized caves

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Agrobacterium fabrum C58 involved nitrate reductase NapA and antisense RNA NorR to denitrify

International audienceABSTRACT Agrobacterium fabrum C58 is a plant-associated bacterium that is able to denitrify under anoxic conditions. The cluster of denitrification genes harbored by this strain has been well characterized. It includes nir and nor operons encoding nitrite and nitric oxide reductases, respectively. However, the reductase involved in nitrate reduction has not yet been studied and little information is available on denitrification regulators in A. fabrum C58. In this study, we aimed to (i) characterize the nitrate reductase, (ii) determine its role in A. fabrum C58 fitness and root colonization and (ii) reveal the contribution of small RNA on denitrification regulation. By constructing a mutant strain defective for napA, we demonstrated that the reduction of nitrate to nitrite was catalyzed by the periplasmic nitrate reductase, NapA. We evidenced a positive role of NapA in A. fabrum C58 fitness and suggested that A. fabrum C58 is able to use components exuded by plant roots to respire anaerobically. Here, we showed that NorR small RNA increased the level of norCBQ mRNA and a decrease of NorR is correlated with a decrease in N2O emission. Together, our results underscore the importance of understanding the denitrification pathway at the strain level in order to develop strategies to mitigate N2O production at the microbial community level

16SrRNA of bacteria associated to H. armigera

16SrRNA gene sequences of eight bacterial isolates isolated from dead H. armigera larvae. </p

Housekeeping gene sequences for MLSA

Seven gene sequences of a bacterial isolate named Hr1 that has shown an interesting insecticidal effect against Helicoverpa armigera larvae.  The bacterial isolate was identified as Bacillus thuringiensis gv cytoliticus following an MLSA technique. </p