Molecular mechanisms involved in the bacterial talking and maize growth promotion

Abstract

Molecular mechanisms involved in the bacterial talking and maize growth promotion With the increase of agricultural production, there is an improvement in the use of mineral fertilizers, which may cause different environmental problems, besides the soil salinization. A possible alternative for reducing the application of these products is the use of plant growth-promoting bacteria (PGPB), that can be used alone or in co-inoculation, resulting in an alternative environmentally and economically feasible. Better results can be obtained if the interaction among bacteria-bacteria and bacteria-plant be elucidated, and strategy developed to optimize these interactions. Thus, the plant growth-promoting Bacillus sp. RZ2MS9, previous described as a potential PGPB in maize and soybean, was GFP-tagged and monitored alone and co-inoculated with Azospirillum brasilense (Ab-v5::pWM1013) during maize colonization. The interaction of tagged strains in maize were monitored by fluorescent microscopy (FM) and quantitative PCR (qPCR), demonstrating an endophytic behavior of Bacillus sp. RZ2MS9. Although the non-detection of Ab-v5::pWM1013, the co-inoculation resulted in the best increase in root and shoot dried weight, root volume and in root diameter, showing that inoculation with more than one strain can be a good choice to development of bio-fertilizers. One important system to bacterial interaction is the quorum sensing (QS). The QS is an important cell-cell communication system that allows bacterial cells to recognize their own population and modulate their gene expression. This, system is also involved in the interspecific communication, including other bacterial species and plants. In the other hand, enzymes able to detect and degrade these molecules evolved, the called quorum quenching (QQ) system, that has been evolved in some bacteria as competitive advantage for niches colonization. The aiiA gene, was one of the first gene related with the QQ in Bacillus. The aiiA was found in Bacillus sp. RZ2MS9 genome. Through construction of a new QQ biosensor, Agrobacterium tumefaciens At11006, and validated by A. tumefaciens NTL4, the ability of RZ2MS9 to degrade QS molecules was confirmed. The knockout of aiiA gene was performed using the CRISPR-Cas9 system, confirming this gene function. By these results, the influence of QQ system of Bacillus sp. RZ2MS9 during maize colonization and RZ2MS9-A. brasilense-maize can be better investigated, opens the possibility to better understand the role of QQ system in the interaction among PGPB and plants.

Simultaneous Impact of Rhizobacteria Inoculation and Leaf-Chewing Insect Herbivory on Essential Oil Production and VOC Emissions in Ocimum basilicum

“…This differs from a previous study on M. piperita, which registered an increase in VOCs after inoculation with GB03 or co-inoculation with GB03 and Pseudomonas putida SJ04 [65]. An increase in total VOCs was also observed in other non-aromatic crops, such as maize inoculated with B. thuringiensis RZ2MS9 or co-inoculated with RZ2MS9 and Azospirillum brasilense Ab-v5 [66].…”