Background: The humic acid (HA) fraction of soil organic matter (SOM) exerts an effective plant growth promotion through a complex mechanism involving a coordinated activation of several key ion transport and signaling systems. We investigated the effects of HA on H⁺and Ca²⁺cellular dynamics at the early stages of lateral plant root development.Results: Emergence of lateral root in rice seedlings were related to specific H⁺and Ca²⁺fluxes in the root elongation zone underlying an activation of the plasma membrane H⁺-ATPase and of the Ca²⁺-dependent protein kinase (CDPK). The latter was coupled with an increased expression of the voltage-dependentOsTPC1Ca²⁺channels and two stress responsive CDPK isoforms, such asOsCPK7andOsCPK17.Conclusions: HA act as molecular elicitors of H⁺and Ca²⁺fluxes, which seem to be upstream of a complex CDPK cell-signaling cascade. These findings shed light on the first ion signaling events involved in the mechanism of action of HA on plant growth and development.

• Ion dynamics are important for cell nutrition and growth in fungi and plants. Here, the focus is on the relationship between the hyphal H⁺ fluxes and the control of presymbiotic growth and host recognition by arbuscular mycorrhizal (AM) fungi. • Fluxes of H⁺ around azygopores and along lateral hyphae of Gigaspora margarita during presymbiotic growth, and their regulation by phosphate (P) and sucrose (Suc), were analyzed with an H⁺-specific vibrating probe. Changes in hyphal H⁺ fluxes were followed after induction by root exudates (RE) or by the presence Trifolium repens roots. • Differential sensitivity to P-type ATPase inhibitors (orthovanadate or erythrosin B) suggests an asymmetric distribution or activation of H⁺-pump isoforms along the hyphae of the AM fungi. Concentration of P and Suc affected the hyphal H⁺ fluxes and growth rate. However, further increases in H+ efflux and growth rate were observed when the fungus was growing close to clover roots or pretreated with RE. • The H⁺ flux data correlate with those from polarized hyphal growth analyses, suggesting that spatial and temporal alterations of the hyphal H⁺fluxes are regulated by nutrient availability and might underlie a pH signaling elicitation by host RE during the early events of the AM symbiosis.

The ability of mosquitoes of the genus Aedes and its allies, such as Stegomyia, to transmit diseases such as dengue and yellow fever, makes them important in public health. This study aims to evaluate the use of the essential oil of Brazilian pepper in biological control of by assessing and quantifying the larvicidal effect against S. aegypti, the only available access to dengue control, and test its risk of genotoxicity with Salmonella typhimurium as an indicator of safety for its environmental use.

Achieving food security in a context of environmental sustainability is one of the main challenges of the XXI century. Two competing strategies to achieve this goal are the use of genetically modified plants and the use of plant growth promoting microorganisms (PGPMs). However, few studies assess the response of genetically modified plants to PGPMs. The aim of this study was to compare the response of over-expressing the vacuolar H⁺-PPase (AVP) and wild-type rice types to the endophytic fungus; Piriformospora indica. Oryza sativa plants (WT and AVP) were inoculated with P. indica and 30 days later, morphological, ecophysiological and bioenergetic parameters, and nutrient content were assessed. AVP and WT plant heights were strongly influenced by inoculation with P. indica, which also promoted increases in fresh and dry matter of shoot in both genotypes. This may be related with the stimulatory effect of P. indica on ecophysiological parameters, especially photosynthetic rate, stomatal conductance, intrinsic water use efficiency and carboxylation efficiency. However, there were differences between the genotypes concerning the physiological mechanisms leading to biomass increment. In WT plants, inoculation with P. indica stimulated all H⁺ pumps. However, in inoculated AVP plants, H⁺-PPase was stimulated, but P- and V-ATPases were inhibited. Fungal inoculation enhanced nutrient uptake in both shoots and roots of WT and AVP plants, compared to uninoculated plants; but among inoculated genotypes, the nutrient uptake was lower in AVP than in WT plants. These results clearly demonstrate that the symbiosis between P. indica and AVP plants did not benefit those plants, which may be related to the inefficient colonization of this fungus on the transgenic plants, demonstrating an incompatibility of this symbiosis, which needs to be further studied.