Mariana Miranda-Arámbula

Soil microbial diversity is of great importance for plant development, as well as for the control of pathogens through the production of metabolites. In this study, the effect of the compound 22-Oxocholestanes SPGP4, an analogue of brassinosteroids, on microbial diversity was evaluated when applied to soils where maize and beans are grown. The soils were analyzed using metagenomic study to determine the populations of bacteria and fungi before and after the application of the compound. The results show that the main bacterial Phyla are Actinobacteria, Acidobacteriota, and Proteobacteria; while the main genera are Bacillus, Streptomyces, Nocardioides, Vicinamibacteraceae, Solirubrobacter and Sphingomonas were the most abundant. With regard to fungi, the main Phyla were Ascomycota and Basidiomycota; the main genera being Aspergillus, Fusarium, Chrysocorona, Penicillium, Humicola, Chaetomium and Curvularia. The alpha diversity showed that there was no significant difference (p> 0.05) in the soil microbial communities, which indicates that the application of 22-Oxocholestanes SPGP4 at a concentration of 0.5 mg/L does not affect the microbial diversity of the soils.

The search for new plant growth regulators is a cornerstone of agricultural research; however, laboratory studies rarely go on to be evaluated in the field. This is because greater production is required, as well as longer studies. Particularly, brassinosteroids present these difficulties, and although they have been evaluated in crops with good results, their high production cost gives rise to the search for new alternatives. 22-Oxocholestanes such as SPGP4, previously used in silico and in vitro studies, have shown great potential, so their evaluation in crops grown from native seeds from the study region becomes of interest. Based on these data, SPGP4 was evaluated under crop conditions in three agricultural plots located on the Isthmus of Tehuantepec region, Oaxaca, México. The seeds were treated with a 0.5 mg/L aqueous solution of the 22-Oxocholestane compound SPGP4 by imbibition one night before sown. Later, 45 days after sowing, a solution of 0.5 mg/L at a rate of 200 L per hectare was applied. At the production level, the bean harvest showed an increase in the range of 21.0–38.1%, and the corn harvest increased between 22 and 32%. In addition, the latter also demonstrated an increase in biomass production, given the increase in diameter and height observed in the corn plant. This indicates that SPGP4 functions as a regulator of plant growth at the crop level to increase both seed and biomass production.

The 22‐oxocholestanes compounds have shown an outstanding plant growth promoting activity; they have similar bioactivity as brassinosteroids, so they are normally named as brassinosteroid analogs thinking that they also impact on the known receptor BRI1. However, in silico studies allow us to predict interactions with other receptors and thus it's possible to evaluate them, through receptors of gibberellins, auxins, jasmonates, strigolactones and the protein associated with the BRI1 gene. This article describes the bioactivity of structures SPGP4 and SPGP8 as plant growth‐promoting compounds. Both structures present coupling energies and interactions at the same level as epibrassinolide in the protein associated with BRI1 gene. Additionally, interactions through the auxin pathway and to strigolactone receptor were found using selected tests. In the rice lamina tilt, a higher effect was obtained when SPGP4 and SPGP8 were compared to epibrassinolide, although in a lesser level vis à vis to homobrassinolide. In the same way, when SPGP4 and SPGP8 were tested in the Growth Root Model an activity as strigonolactones was observed, enhancing the relationship between the main and secondary roots. However, the growth of coleptiles, when applying auxins, compounds SPGP4 and SPGP8 did not reach the same level as controls. In the tests associated to gibberellins and jasmonic acid, an increased bioactivity was observed, although this behavior was not reflected from the in silico study, possibly due to secondary signaling cascades. This work demonstrates that the 22‐oxocolestane compounds SPGP4 and SPGP8 could be used as plant growth hormones, promoting several pathways.

El uso exitoso de las nanopartículas (NP) en diversos sectores ha incrementado el interés y la demanda para sintetizarlas, explorarlas y estudiarlas. La síntesis de NP (tanto como sus derivados, reducciones, funcionalizaciones, o conjugaciones), sus propiedades y aplicaciones se han analizado desde enfoques modernos, a través de diversas técnicas de avanzada, para aplicaciones múltiples. El objetivo de este trabajo es destacar la importancia de las plantas silvestres o cultivables de México como fuente de metabolitos y extractos, empleadas como origen y medio de síntesis de NP. Asimismo, se destaca la síntesis verde como un método amigable con el medioambiente para aprovechar la amplia gama de posibilidades que representa el reservorio natural de plantas mexicanas y sus diversas aplicaciones y propiedades a explorar en el campo de la nanobiotecnología.

Background: The application of synthetic pesticides to the tomato crop ( Solanum lycopersicum -Solanaceae-) increases fruit production, but also carries risks for the environment, human and animal health. Hypothesis: local ruderal plant extracts could be an alternative for weed control, with potential applications in agroecology and organic agriculture. Methods: Organic and aqueous extracts (1 and 10% w/v) were prepared with the fresh (FAE) and dry (DAE) aerial parts of five ruderal species from Tlaxcala, Mexico: Argemone mexicana L. (Papaveraceae), Baccharis salicifolia Pers. (Asteraceae), Lepidium virginicum L. (Brassicaceae), Leucena leucocephala S. Zárate (Fabaceae) and Reseda luteola L. (Resedaceae). Their phytotoxic activity was evaluated in vitro with the seeds of three model plants (amaranth, lettuce, and tomato). Results: DAE of B. salicifolia and L. virginicum (1 % w/v) showed the highest potential as natural herbicides. These inhibited 100 % seed germination and radicle elongation in the three model plants but did not affect the growth of tomato seedlings of 8 and 12 weeks in greenhouse conditions. Both extracts analyzed by HPLC-ESI-QTOF-MS showed two major peaks. Bacharis salicifolia with m/z 432.9 and 725.4. Lepidium virginicum with m/z 532.9 and 527.1. Conclusions:DAE of local ruderal plants B. salicifolia and L. virginicum (1 % w/v) are potential natural herbicides, without harmful effects on tomato cultivated seedlings, awaiting the precise identification of their active compounds.

Since engineering nanoparticles (ENP) have been developed for using in industry and human commodities, is common to find their wastes and by-products from industrial chemical reactions, and it is also possible to find incidental nanoparticles in the environment. Currently, the remediation of polluted soils using nanotechnologies has become an emerging area with a huge potential to improve the performance of traditional remediation technologies. However, environmental concerns have also emerged regarding human and environmental health when nanotechnologies are released to ecosystems. The goal of this manuscript is to highlight the environmental benefits and risks that arise when nanotechnologies are used to remediate polluted soils. We searched Web of Science and Scopus in order to get latest updated information and patents pertaining to developments in the field of nanotechnologies for decontaminating soils. It has been determined that soil nanoremediation has some advantages, but it also has some disadvantages related to the final disposal of nanoparticles, nanomaterials, or nanodevices. Will some nanotechnologies be our pitfall? Nanoparticle toxicity has to be assessed and the standardization of techniques should be set by scientists and decision-makers worldwide. Cutting-edge knowledge regarding the use of nanoparticles to decontaminate soils has to move forward, but environmental quality, human health, and social welfare should also be ensured.