Endophytic fungi infect plant tissues by evading the immune response, potentially stimulating stress-tolerant plant growth. The plant selectively allows microbial colonization to carve endophyte structures through phenotypic genes and metabolic signals. Correspondingly, fungi develop various adaptations through symbiotic signal transduction to thrive in mycorrhiza. Over the past decade, the regulatory mechanism of plant-endophyte interaction has been uncovered. Currently, great progress has been made on plant endosphere, especially in endophytic fungi. Here, we systematically summarize the current understanding of endophytic fungi colonization, molecular recognition signal pathways, and immune evasion mechanisms to clarify the transboundary communication that allows endophytic fungi colonization and homeostatic phytobiome. In this work, we focus on immune signaling and recognition mechanisms, summarizing current research progress in plant-endophyte communication that converge to improve our understanding of endophytic fungi.

A Critical Review on Communication Mechanism within Plant-Endophytic Fungi Interactions to Cope with Biotic and Abiotic Stresses

Plants host numerous endophytic microbes which promote plant performance, in particular under stress. A new endophytic fungus was isolated from the leaves of a deciduous wood tree Leucas aspera. Morphological inspection and multilocus phylogeny identified the fungus as a new Trichoderma strain. If applied to Arabidopsis thaliana and Nicotiana attenuata, it mainly colonizes their roots and strongly promotes initial growth of the plants on soil. The fungus grows on high NaCl or mannitol concentrations, and shows predatory capability on the pathogenic fungus Alternaria brassicicola. Colonized Arabidopsis plants tolerate higher salt stress and show lower A. brassicicola spread in roots and shoots, while arbuscular mycorrhiza formation in N. attenuata is not affected by the Trichoderma strain. These beneficial features of the novel Trichoderma strain are important prerequisites for agricultural applications.

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An Endophytic Trichoderma Strain Promotes Growth of Its Hosts and Defends Against Pathogen Attack.

Biocontrol mechanisms of Trichoderma harzianum ITEM 3636 against peanut brown root rot caused by Fusarium solani RC 386

In vitro and in silico approach of fungal growth inhibition by Trichoderma asperellum HbGT6-07 derived volatile organic compounds

Wheat is among the top 10 and most widely grown crops in the world. However, wheat is often infected with many soil-borne diseases, including sharp eyespot, mainly caused by the necrotrophic fungus Rhizoctonia cerealis, and Fusarium head blight (FHB), caused by Fusarium graminearum, resulting in reduced production. Piriformospora indica is a root endophytic fungus with a wide range of host plants, which increases their growth and tolerance to biotic and abiotic stresses. In this study, the capability of P. indica to protect wheat seedlings against R. cerealis and F. graminearum was investigated at the physiological, biochemical, and molecular levels. Our results showed that P. indica significantly reduced the disease progress on wheat caused by F. graminearum and R. cerealis in vivo, but not showed any antagonistic effect on F. graminearum and R. cerealis in vitro. Additionally, P. indica can induce systemic resistance by elevating H2O2 content, antioxidase activity, relative water content (RWC), and membrane stability index (MSI) compared to the plants only inoculated with F. graminearum or R. cerealis and control. RNA-seq suggested that transcriptome changes caused by F. graminearum were more severe than those caused by R. cerealis. The number of differentially expressed genes (DEGs) in the transcriptome can be reduced by the addition of P. indica: for F. graminearum reduced by 18% and for R. cerealis reduced 58%. The DEGs related to disease resistance, such as WRKY and MAPK, were upregulated by P. indica colonization. The data further revealed that the transcriptional resistance to F. graminearum and R. cerealis mediated by P. indica is quite different.

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Effect of Piriformospora indica-Induced Systemic Resistance and Basal Immunity Against Rhizoctonia cerealis and Fusarium graminearum in Wheat

Inhibition of plant pathogenic fungi by endophytic Trichoderma spp. through mycoparasitism and volatile organic compounds.

Colchicine, a well-known alkaloid, is a potent inhibitor of polymerization of tubulin leading to mitotic arrest. It is highly toxic to eukaryotic cells but also widely used in the field of medicine and plant breeding. Gloriosa superba (family: Colchicaceae) is an important natural source of colchicine. The seeds, tubers and leaves of this plant contain about 0.8, 1.2 and 0.014% colchicine by dry weight respectively. A noctuid moth, Polytela gloriosae (family: Noctuidae), feeds voraciously on leaves of G. superba without any adverse effect. However, the fate of colchicine and the mechanisms by which the insect is able to overcome the toxicity of the metabolite is not known. Here, we trace the fate of colchicine in both, the larva and moth of P. gloriosae. Colchicine was quantified in different body parts of the larvae and moth by high performance liquid chromatography, liquid chromatography mass spectrophotometry and nuclear magnetic resonance methods. Of the total colchicine taken in by the larva, a larger portion was excreted, while the rest was sequestered in its cuticle. In the moths however, the wings, legs and antennae were found to accumulate high amount of colchicine. The sequestered colchicine, in both the larva and adult, were chemically identical to that found in the plant. Negligible amounts of demethyl-(−)-colchicine, a less toxic derivative of colchicine was also detected. We discuss the probable adaptive significance of sequestration of colchicine by the insect.

P. Rajani

Papers

Inhibition of plant pathogenic fungi by endophytic Trichoderma spp. through mycoparasitism and volatile organic compounds.

Sequestration of the plant secondary metabolite, colchicine, by the noctuid moth Polytela gloriosae (Fab.)