Endophyte
Encyclopedia
An endophyte is an endosymbiont
, often a bacterium or fungus
, that lives within a plant
for at least part of its life without causing apparent disease. Endophytes are ubiquitous and have been found in all the species of plants studied to date; however, most of these endophyte/plant relationships are not well understood. Many economically important forage and turfgrasses (e.g., Festuca spp., Lolium spp.) carry fungal endophytes (Neotyphodium
spp.) which may improve the ability of these grasses to tolerate abiotic stresses such as drought, as well as improve their resistance to insect and mammalian herbivores.
and transmit via fungal
hyphae
penetrating the host’s seed
s (e.g. Neotyphodium
). Since their reproductive fitness is intimately tied to that of their host plant, these fungi are often mutualistic. Conversely, horizontally transmitted fungal endophytes are sexual
and transmit via spore
s that can be spread by wind and/or insect vectors. Since they spread in a similar way to pathogens, horizontally transmitted endophytes are often closely related to pathogen
ic fungi, though they are not pathogenic themselves.
is a very common phenomenon, primarily involving the arbuscular mycorrhizal fungi
.
: Pestalotiopsis
microspora, an endophytic fungus of Taxus wallachiana (Himalayan Yew) was found to produce taxol . Endophytes are also being investigated for roles in agriculture and biofuels production. Inoculating crop plants with certain endophytes may provide increased disease or parasite resistance while others may possess metabolic processes that convert cellulose and other carbon sources into "myco-diesel" hydrocarbons and hydrocarbon derivatives. Piriformospora indica is an interesting endophytic fungus of the order Sebacinales
, the fungus is capable of colonising roots and forming symbiotic relationship with every possible plant on earth. P. indica has also been shown to increase both crop yield and plant defence of a variety of crops(barley, tomato, maize etc.) against root-pathogens.
It is speculated that there may be many thousands of endophytes useful to mankind but since there are few scientists working in this field, and since forests and areas of biodiversity are rapidly being destroyed, many useful endophytes for curing disease might be permanently lost for medicinal use before they are discovered. The effects of climate change on endophytes is being investigated. Studies of plants grown at different climates or at increased carbon dioxide levels have different distributions of endophytic species
Endophytes can be identified in several ways, usually through amplifying and sequencing a small piece of DNA. Some endophytes can be cultured from a small piece of their host plant in an appropriate growth medium. Not all endophytes present can be cultured in this way because amplification ground up plant tissue using fungal or bacterial specific primers has revealed the existence cryptic species. Grass leaf endophytes can be seen as coiled tubes of hyphae under the microscope at 400X following clearing of the leaf sheaths in ethanol and staining with aniline blue.
Endosymbiont
An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis...
, often a bacterium or fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
, that lives within a plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
for at least part of its life without causing apparent disease. Endophytes are ubiquitous and have been found in all the species of plants studied to date; however, most of these endophyte/plant relationships are not well understood. Many economically important forage and turfgrasses (e.g., Festuca spp., Lolium spp.) carry fungal endophytes (Neotyphodium
Neotyphodium
Neotyphodium is a form genus containing species of endophytic fungi. These endophytes are asexual, seed-borne symbionts of cool-season grasses, and grow intercellularly throughout the aerial tissues of their hosts, including shoot apical meristems, leaf sheaths and blades, inflorescences, seeds and...
spp.) which may improve the ability of these grasses to tolerate abiotic stresses such as drought, as well as improve their resistance to insect and mammalian herbivores.
Transmission
Endophytes may be transmitted either vertically (directly from parent to offspring) or horizontally (from individual to unrelated individual). Vertically transmitted fungal endophytes are asexualAsexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
and transmit via fungal
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
hyphae
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
penetrating the host’s seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s (e.g. Neotyphodium
Neotyphodium
Neotyphodium is a form genus containing species of endophytic fungi. These endophytes are asexual, seed-borne symbionts of cool-season grasses, and grow intercellularly throughout the aerial tissues of their hosts, including shoot apical meristems, leaf sheaths and blades, inflorescences, seeds and...
). Since their reproductive fitness is intimately tied to that of their host plant, these fungi are often mutualistic. Conversely, horizontally transmitted fungal endophytes are sexual
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
and transmit via spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s that can be spread by wind and/or insect vectors. Since they spread in a similar way to pathogens, horizontally transmitted endophytes are often closely related to pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
ic fungi, though they are not pathogenic themselves.
Endophyte-Host Relationship
Endophytes may benefit host plants by preventing pathogenic organisms from colonizing them. Extensive colonization of the plant tissue by endophytes creates a "barrier effect", where the local endophytes outcompete and prevent pathogenic organisms from taking hold. Endophytes may also produce chemicals which inhibit the growth of competitors, including pathogenic organisms. The presence of fungal endophytes has been shown to cause higher rates of water loss in leaves. Plant use of endophytic fungi in defensePlant use of endophytic fungi in defense
Plant use of endophytic fungi in defense occurs when endophytic fungi, which live symbiotically with the majority of plants by entering their cells, are utilized as an indirect defense against herbivores...
is a very common phenomenon, primarily involving the arbuscular mycorrhizal fungi
Arbuscular mycorrhizal fungi
Arbuscular mycorrhizal fungi are all placed in the phylum Glomeromycota. They form the widespread arbuscular mycorrhiza symbiosis with land plants . The fungi are obligate symbionts that cannot be cultured without a plant as a 'host'...
.
Use
The wide range of compounds produced by endophytes have been shown to combat pathogens and even cancers in animals including humans. One notable endophyte with medicinal benefits to humans was discovered by Dr. Gary StrobelGary Strobel
Dr. Gary A. Strobel is an American microbiologist who was born and raised in Massillon, Ohio. He was co-contributor to the discovery that somaclonal variation occurs in plants and can be used for plant improvement...
: Pestalotiopsis
Pestalotiopsis
Pestalotiopsis is a genus of ascomycete fungi. Pestalotiopsis species are known as plant pathogens.-External links:*...
microspora, an endophytic fungus of Taxus wallachiana (Himalayan Yew) was found to produce taxol . Endophytes are also being investigated for roles in agriculture and biofuels production. Inoculating crop plants with certain endophytes may provide increased disease or parasite resistance while others may possess metabolic processes that convert cellulose and other carbon sources into "myco-diesel" hydrocarbons and hydrocarbon derivatives. Piriformospora indica is an interesting endophytic fungus of the order Sebacinales
Sebacinales
The Sebacinales are an order of fungi in the class Agaricomycetes. Taxa have a widespread distribution and are mostly terrestrial, many forming mycorrhizas with a wide variety of plants, including orchids. The order is monotypic, containing a single family, the Sebacinaceae. There are 8 genera and...
, the fungus is capable of colonising roots and forming symbiotic relationship with every possible plant on earth. P. indica has also been shown to increase both crop yield and plant defence of a variety of crops(barley, tomato, maize etc.) against root-pathogens.
It is speculated that there may be many thousands of endophytes useful to mankind but since there are few scientists working in this field, and since forests and areas of biodiversity are rapidly being destroyed, many useful endophytes for curing disease might be permanently lost for medicinal use before they are discovered. The effects of climate change on endophytes is being investigated. Studies of plants grown at different climates or at increased carbon dioxide levels have different distributions of endophytic species
Identification
While many endophytes are known to colonize multiple species of plants, some are host specific. Endophytic species are very diverse; it is thought that only a small minority of all existing endophytes have been characterized. A single leaf of a plant can harbor many different species of endophytes, both bacterial and fungal.Endophytes can be identified in several ways, usually through amplifying and sequencing a small piece of DNA. Some endophytes can be cultured from a small piece of their host plant in an appropriate growth medium. Not all endophytes present can be cultured in this way because amplification ground up plant tissue using fungal or bacterial specific primers has revealed the existence cryptic species. Grass leaf endophytes can be seen as coiled tubes of hyphae under the microscope at 400X following clearing of the leaf sheaths in ethanol and staining with aniline blue.