LC-ESI-HRMS-Based Chemical Characterization of Lupinus bogotensis Roots

Plants of the genus Lupinus (Fabaceae) have been studied due to the occurrence of different compounds, especially those possessing quinolizidine and isoflavone-like structures. These kinds of compounds are characterized by both medical and industrial applications, providing various benefits to human being. However, organs such as roots have not been equally studied and there is a lack of such records for native species. Therefore, in the present study, the chemical composition of nodulated roots from greenhouse-established L. bogotensis plants was determined. The resulting crude ethanolic extract was then analyzed by LC/HRMS and chemical nature of most compounds was determined by analyzing the high resolution mass spectra. Recorded profile showed adequate separation allowing tentative identification of detected compounds. 47 secondary metabolites (mainly isoflavones and quinolizidine-type compounds) were thus identified. Most phenolic compounds were found to be conjugated flavonoids (e.g., genistin and genistein malonylglucoside) and lupanine, sparteine and hydroxylupanine were noticed as the main alkaloids. Among alkaloid-like compounds, dehydromitomycin C, a compound produced by Streptomyces caespitosus was identified. Lupadienediol (a lupane-type triterpene recognized for being involved in rhizobacteria:legumes symbiosis) was the only terpene-related component identified in the extract. The present work corresponds to the first report on the chemical composition of L. bogotensis root and constitutes an adequate basis for phytoconstituents finding from nature to support the use of native species

Enterobacter cloacae, an Endophyte That Establishes a Nutrient-Transfer Symbiosis With Banana Plants and Protects Against the Black Sigatoka Pathogen

Banana (Musa spp.) is an important crop worldwide, but black Sigatoka disease caused by the fungus Pseudocercospora fijiensis threatens fruit production. In this work, we examined the potential of the endophytes of banana plants Enterobacter cloacae and Klebsiella pneumoniae, as antagonists of P. fijiensis and support plant growth in nutrient limited soils by N-transfer. The two bacterial isolates were identified by MALDI-TOF mass spectrometry and corroborated by 16S rRNA sequence analysis. Both bacteria were positive for beneficial traits such as N-fixation, indole acetic acid production, phosphate solubilization, negative for 1-aminocyclopropane 1-carboxylic acid deaminase and were antagonistic to P. fijiensis. To measure the effects on plant growth, the two plant bacteria and an E. coli strain (as non-endophyte), were inoculated weekly for 60 days as active cells (AC) and heat-killed cells (HKC) into plant microcosms without nutrients and compared to a water only treatment, and a mineral nutrients solution (MMN) treatment. Bacterial treatments increased growth parameters and prevented accelerated senescence, which was observed for water and mineral nutrients solution (MMN) treatments used as controls. Plants died after the first 20 days of being irrigated with water; irrigation with MMN enabled plants to develop some new leaves, but plants lost weight (−30%) during the same period. Plants treated with bacteria showed good growth, but E. cloacae AC treated plants had significantly greater biomass than the E. cloacae HKC. After 60 days, plants inoculated with E. cloacae AC showed intracellular bacteria within root cells, suggesting that a stable symbiosis was established. To evaluate the transference of organic N from bacteria into the plants, the 3 bacteria were grown with 15NH4Cl or Na15NO3 as the nitrogen source. The 15N transferred from bacteria to plant tissues was measured by pheophytin isotopomer abundance. The relative abundance of the isotopomers m/z 872.57, 873.57, 874.57, 875.57, 876.57 unequivocally demonstrated that plants acquired 15N atoms directly from bacterial cells, using them as a source of N, to support plant growth in restricted nutrient soils. E. cloacae might be a new alternative to promote growth and health of banana crops