Characterization of biocontrol traits of heterorhabditid entomopathogenic nematode isolates from South Benin targeting the termite pest Macrotermes bellicosus

Twenty-nine Beninese isolates of Heterorhabditis sonorensis and one local isolate of H. indica were screened in bioassays for their pathogenicity against Macrotermes bellicosus and for their tolerance to heat (40 °C), desiccation (25 % glycerine) and hypoxic conditions. The bioassays showed significant differences among isolates for all tested traits. Most of the isolates (73 %) killed more than 80 % of the insects. The greatest survival of infective juveniles to heat (8 h), desiccation (8 h), and hypoxia (72 h) was observed with the H. sonorensis isolates Kassehlo (72.8 %), Setto1 (72.5 %), and Kissamey (81.5 %, respectively). Hierarchical cluster analysis identified six clusters. One of the clusters grouped three isolates of H. sonorensis (Zoundomey, Akohoun and Kassehlo) that scored well for all traits. These latter isolates were similarly effective by suppressing within five days a population of M. bellicosus naturally imprisoned in 1,000 cm³ containers and inoculated with a single two-weeks-old EPN-infected Galleria larva.     

Development of a Sensitive Serological Method for Specific Detection of Latent Infection of Macrophomina phaseolina in Cowpea

A double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for the specific detection and quantification of Macrophomina phaseolina in plant tissue. Both polyclonal antisera produced against immunogens from mycelium and culture filtrate of M. phaseolina detected the fungus in mycelial and plant extracts, although the antibodies raised against mycelium were more sensitive. No cross-reaction occurred with Rhizopus stolonifer , Pythium ultimum , Mucor hiemalis , Fusarium oxysporum , Septoria nodorum , Rhizoctonia solani , Sclerotinia sclerotiorum , Phytophthora infestans and Aspergillus niger . In enzyme assays, activity of the endo-acting hydrolytic enzymes 1,3-β-glucanase and, less, cellulase, but not xylanase was detected in infected plants. DAS-ELISA was more sensitive than the 1,3-β-glucanase assay. In polyacrylamide gel electrophoresis (PAGE) up to 18 protein bands were observed, with four bands occurring in the 12 tested isolates deriving from various geographical origin in Niger and Nigeria. The enzyme assays and protein patterns were considered not suitable for specific M. phaseolina detection. Macrophomina phaseolina was essentially located in the roots and hypocotyls, and less in epicotyls and leaves of infected plants. The antibodies were also useful to detect latent infection and the infection of cowpea seeds.     

GATA4, 5 and 6 mediate TGFbeta maintenance of endodermal gene expression in Xenopus embryos

The individual contributions of the three vertebrate GATA factors to endoderm formation have been unclear. Here we detail the early expression of GATA4, 5 and 6 in presumptive endoderm in Xenopus embryos and their induction of endodermal markers in presumptive ectoderm. Induction of HNF3beta by all three GATA factors was abolished when protein synthesis was inhibited, showing that these inductions are indirect. In contrast, whereas induction of Sox17alpha and HNF1beta by GATA4 and 5 was substantially reduced when protein synthesis was inhibited, induction by GATA6 was minimally affected, suggesting that GATA6 is a direct activator of these early endodermal genes. GATA4 induced GATA6 expression in the same assay and antisense morpholino oligonucleotides (MOs), designed to knock down translation of GATA6, blocked induction of Sox17alpha and HNF1beta by GATA4, suggesting that GATA4 induces these genes via GATA6 in this assay. All three GATA factors were induced by activin, although GATA4 and 6 required lower concentrations. GATA MOs inhibited Sox17alpha and HNF1beta induction by activin at low and high concentrations in the order: GATA6>GATA4>GATA5. Together with the timing of their expression and the effects of GATA MOs in vivo, these observations identify GATA6 as the predominant GATA factor in the maintenance of endodermal gene expression by TGFbeta signaling in gastrulating embryos. In addition, examination of gene expression and morphology in later embryos, revealed GATA5 and 6 as the most critical for the development of the gut and the liver.