In Vitro Morphogenesis of Arabidopsis to Search for Novel Endophytic Fungi Modulating Plant Growth

Abstract

Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E) and roots (root-E) of Mentha aquatica L. (water mint) were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L.) Heynh., 14 and 21 days after inoculation (DAI). Nineteen fungi were analysed and, based on ITS analysis, 17 isolates showed to be genetically distinct. The overall effect of water mint endophytes on Arabidopsis fresh (FW) and dry weight (DW) was neutral and positive, respectively, and the increased DW, mainly occurring 14 DAI, was possibly related to plant defence mechanism. Only three fungi increased both FW and DW of Arabidopsis at 14 and 21 DAI, thus behaving as plant growth promoting (PGP) fungi. E-treatment caused a reduction of root depth and primary root length in most cases and inhibition-to-promotion of root area and lateral root length, from 14 DAI. Only Phoma macrostoma, among the water mint PGP fungi, increased both root area and depth, 21 DAI. Root depth and area 14 DAI were shown to influence DWs, indicating that the extension of the root system, and thus nutrient uptake, was an important determinant of plant dry biomass. Reduction of Arabidopsis root depth occurred to a great extent when plants where treated with stem-E while root area decreased or increased under the effects of stem-E and root-E, respectively, pointing to an influence of the endophyte origin on root extension. M. aquatica and many other perennial hydrophytes have growing worldwide application in water pollution remediation. The present study provided a model for directed screening of endophytes able to modulate plant growth in the perspective of future field applications of these fungi.

Ecologically Different Fungi Affect Arabidopsis Development: Contribution of Soluble and Volatile Compounds

“…thaliana is becoming a recognized model to analyse both mutualistic and non-mutualistic plant-microbe interactions [71–74], and several PGPFs have been shown to promote growth of this plant in vitro [6,17,19]. We have confirmed this observation for ERM fungi, as well as for other mycorrhizal and non-mycorrhizal fungi.…”

“…Enhanced A . thaliana root development and branching was reported also for three endophytic fungi isolated from Mentha aquatica [19]. Two free-living fungi, Trichoderma virens and Trichoderma atroviride , enhanced LR growth when co-cultured with A .…”

“…Other fungi tested for comparison also promoted A . thaliana growth and influenced plant development, with some of them causing the peculiar clumped root phenotype, a behavior that may be quite widespread among soil fungi (this work; [19]). The ability to increase plant growth and to modify plant development and root architecture is largely documented for both PGPRs and PGPFs.…”

“…thaliana in the presence of both bacteria and fungi [6,11,19,31]. Although auxin can induce primary root growth inhibition and has been suggested to be responsible for this particular phenotype in A .…”

“…Several non-mutualistic fungi and root-associated endophytic fungi have been described in the literature as PGPF. Among them are strains belonging to the genera Penicillium , Fusarium , Phoma , Trichoderma , Ampelomyces , Coniothyrium , Aspergillus , Sarocladium , Ophiosphaerella , Piriformospora [6,13–19]. The mycorrhizal symbiosis facilitates water and nutrient absorption and positively affects plant growth [20].…”