RESUMEN

Most fungi are known to synthesize siderophores under iron limitation. However, arbuscular mycorrhizal fungi (AM fungi) have so far not been reported to produce siderophores, although their metabolism is iron-dependent. In an approach to isolate siderophores from AM fungi, we have grown plants of Tagetes patula nana in the presence of spores from AM fungi of the genus Glomus (G. etunicatum, G. mossae & unidentified Glomus sp.) symbiotically under iron limitation and sterile conditions. A siderophore was isolated from infected roots after 2-3 weeks of growth in pots containing low-iron sand with Hoagland solution. HPLC analysis of the root cell lysate revealed a peak at a retention time of 6.7 min which showed iron-binding properties in a chrome azurol S test. The compound was isolated by preparative HPLC and the structure was determined by high resolution electrospray FTICR-MS and GC/MS analysis of the hydrolysis products. From an observed absolute mass to charge ratio (m/z) of 401.11925 [M+H]+ with a relative mass error of ∆ = 0.47 ppm an elemental composition of C16H21N2O10 [M+H]+ was derived, suggesting a molecular weight of 400 Da for glomuferrin. Corresponnding ion masses of m/z 423.10 and m/z 439.06 were asigned to the Na-adduct and K-adduct respectively. A mass of 455.03836 confirmed an Fe- complex with an elemental composition of C16H19N2O10Fe (∆ = 0.15 ppm). GC/MS analysis of the HCl lysate (6 N HCL, 12 h) revealed 1,4 butanediamine. Thus the proposed structure of the isolated siderophore from Glomus species consisted of 1,4 butanediamine amidically linked to two dehydrated citrate residues, similar to the previously identified bis-amidorhizoferrin. Thus, the isolated siderophore (glomuferrin) is a member of the rhizoferrin family previously isolated from fungi of the Mucorales (Zygomycetes).

Asunto(s)

Compuestos Férricos/aislamiento & purificación , Hierro/química , Mucorales/química , Micorrizas/química , Putrescina/aislamiento & purificación , Sideróforos/aislamiento & purificación , Cromatografía Líquida de Alta Presión , Compuestos Férricos/química , Peso Molecular , Mucorales/crecimiento & desarrollo , Mucorales/metabolismo , Micorrizas/crecimiento & desarrollo , Micorrizas/metabolismo , Putrescina/química , Sideróforos/química , Esporas Fúngicas/crecimiento & desarrollo , Esporas Fúngicas/metabolismo , Simbiosis , Tagetes/microbiología

RESUMEN

Azadirachtin-A (Aza-A), a tetranortriterpenoid, found in minuscule amounts in the Neem seed-kernels, has proved to be a potent biopesticide. Given the vast biodiversity of Azadirachta indica (Neem) in India, this study is an overview of four main aspects that corroborate with each other in identifying elite Neem chemotypes based on their Aza-A content. These biomarkers included mycofloral, tissue-cultural, ecomorphometrical and molecular analyses on accessions from five ecogeographically different regions in Andhra Pradesh, India, which high-lighted the characteristics of trees that yielded the highest Aza-A. In essence, extremely-arid-alkaline regions with maximum soil pH (8.05) yielded trees with the highest amount of this biopesticide. Likewise, both VAM and soil fungal diversity and frequency exhibited maximal values in their rhizosphere, whereas it exhibited the least values for percentage moisture and also for several micronutrients measured (P2O5, Zn, Fe and Cu). In vitro studies on seeds with high versus low Aza-A content gave sturdier seedlings in the former; with profusely coiled roots and fibirillar foliage in tissue-culture; in addition to these seeds being more viable. Furthermore, their cotyledons alone exhibited significant amount of Aza-A, as measured by HPLC. Besides this significant difference, the impact of growth factors culminated not only in the variations of several secondary metabolites, but also differences in DNA patterns from various parts of a single in vitro plant. Ecomorphometric analyses clearly indicated that at least eight parameters (seed diameter, soil pH, percentage moisture, K2O, P2O5, Zn, lower lobe serrations and upper-lobe-distance of leaves) were significantly related to the quantitative variations in Aza-A. Finally, PCR analyses exhibited a habitat-based molecular concordance of ISSR and FISSR profiles with Aza-A content among the Neem chemotypes. Their relatedness was based on dendrograms constructed by UPGMA algorithms using similarity-index-values.

RESUMEN

We examined how combinations of parentage, fungicide application, and artificial herbivory influence growth and shoot phosphorus content in pre-reproductive Lotus corniculatus, using young offspring arising from three parental crosses, two of which had one parent in common. Soil with vesicular-arbuscular mycorrhizal (VAM) fungi was treated with either water or benomyl, an anti-VAM fungicide, and added to trays containing groups of four full siblings. There were two experiments; in the first no plants were clipped while in the second two of the four plants were clipped to simulate herbivory. In both experiments plants of the two related crosses accumulated more biomass and total shoot P than did plants of the third cross. Plants inoculated with watertreated soil had greater shoot mass and P concentration than did fungicide-treated replicates but the extent of increase in P concentration varied among crosses. In Experiment 2, clipping reduced root mass and resulted in higher shoot P concentration. In this experiment there was a significant interaction of fungicide application and clipping: both unclipped and clipped plants grew better in soil not treated with fungicide, but the increase in shoot mass, total mass, and total P was greater in unclipped plants. Significant interaction of fungicide treatment and clipping is most likely due to reduced availability of carbon to the roots of clipped plants, resulting in poorer symbiotic functioning.