Ergot (), or ergot fungi, is a group of fungi of the genus Claviceps.
The most prominent member of this group is Claviceps purpurea (rye ergot fungus). This fungus grows on rye and related plants, and produces alkaloids that can cause ergotism in humans and other mammals who consume grains contaminated with its fruiting structure (called ergot sclerotium).ergot , online medical dictionaryergot , Dorland's Medical Dictionary
Claviceps includes about 50 known species, mostly in the tropical regions. Economically significant species include C. purpurea (parasitic on grasses and cereals), C. fusiformis (on pearl millet, buffel grass), C. paspali (on dallis grass), C. africana (on sorghum) and C. lutea (on paspalum). C. purpurea most commonly affects outcrossing species such as rye (its most common host), as well as triticale, wheat and barley. It affects oats only rarely.
C. purpurea has at least three races, or varieties, which differ in their host specificity: G1 – land grasses of open meadows and fields; G2 – grasses from moist, forest and mountain habitats; G3 (C. purpurea var. spartinae) – salt marsh grasses (Spartina, Distichlis).
Life cycle An ergot kernel, called a sclerotium, develops when a spore of fungal species of the genus Claviceps infects a floret of flowering grass or cereal. The infection process mimics a pollen grain growing into an ovary during fertilization. Infection requires that the fungal spore have access to the stigma; consequently, plants infected by Claviceps are mainly outcrossing species with open flowers, such as rye (Secale cereale) and ryegrasses (genus Lolium). The proliferating fungal mycelium then destroys the plant ovary and connects with the vascular bundle originally intended for seed nutrition. The first stage of ergot infection manifests itself as a white soft tissue (known as sphacelia) producing sugary honeydew, which often drops out of the infected grass florets. This honeydew contains millions of asexual spores (conidia), which insects disperse to other florets. Later, the sphacelia convert into a hard dry sclerotium inside the husk of the floret. At this stage, alkaloids and lipids accumulate in the sclerotium.
Claviceps species from tropic and subtropic regions produce macro- and microconidia in their honeydew. Macroconidia differ in shape and size between the species, whereas microconidia are rather uniform, oval to globose (5×3 μm). Macroconidia are able to produce secondary conidia. A germ tube emerges from a macroconidium through the surface of a honeydew drop and a secondary conidium of an oval to pearlike shape is formed, to which the contents of the original macroconidium migrates. Secondary conidia form a white, frost-like surface on honeydew drops and spread via the wind. No such process occurs in Claviceps purpurea, Claviceps grohii, Claviceps nigricans and Claviceps zizaniae, all from northern temperate regions.
When a mature sclerotium drops to the ground, the fungus remains dormant until proper conditions (such as the onset of spring or a rain period) trigger its fruiting phase. It germinates, forming one or several fruiting bodies with heads and stipes, variously coloured (resembling a tiny mushroom). In the head, threadlike sexual spores form, which are ejected simultaneously when suitable grass hosts are flowering.
Ergot infection causes a reduction in the yield and quality of grain and hay, and if livestock eat infected grain or hay it may cause a disease called ergotism. Black and protruding sclerotia of C. purpurea are well known. However, many tropical ergots have brown or greyish sclerotia, mimicking the shape of the host seed. For this reason, the infection is often overlooked.
Insects, including flies and moths, carry conidia of Claviceps species, but it is unknown whether insects play a role in spreading the fungus from infected to healthy plants.
Evolution Regarding the evolution of plant parasitism in the Clavicipitaceae, an amber fossil discovered in 2020 preserves a grass spikelet and an ergot-like parasitic fungus. The fossil shows that the original hosts of the Clavicipitaceae could have been grasses. The discovery also establishes a minimum time for the conceivable presence of psychotropic compounds in fungi. Several evolutionary processes have acted to diversify the array of ergot alkaloids produced by fungi; these differences in enzyme activities are evident at the levels of substrate specificity (LpsA), product specification (EasA, CloA) or both (EasG and possibly CloA). The "old yellow enzyme", EasA, presents an outstanding example. This enzyme catalyzes reduction of the C8=C9 double-bond in chanoclavine I, but EasA isoforms differ in whether they subsequently catalyze reoxidation of C8–C9 after rotation. This difference distinguishes most Clavicipitaceae from Trichocomaceae, but in Clavicipitaceae it is also the key difference dividing the branch of classical ergot alkaloids from dihydroergot alkaloids, the latter often being preferred for pharmaceuticals due to their relatively few side effects.
Effects on humans, other mammals and LSD
The ergot sclerotium contains high concentrations (up to 2% of dry mass) of the alkaloid ergotamine, a complex molecule consisting of a tripeptide-derived cyclol-lactam ring connected via amide linkage to a lysergic acid (ergoline) moiety, and other alkaloids of the ergoline group that are biosynthesized by the fungus. Ergot alkaloids have a wide range of biological activities, including effects on circulation and neurotransmission.
Ergot alkaloids are classified as: derivatives of 6,8-dimethylergoline and lysergic acid derivatives.
Ergotism is the name for sometimes severe pathological syndromes affecting humans or other animals that have ingested plant material containing ergot alkaloid, such as ergot-contaminated grains.
The Hospital Brothers of St. Anthony, an order of monks established in 1095, specialized in treating ergotism victims with balms containing tranquilizing and circulation-stimulating plant extracts. The common name for ergotism is "St. Anthony's fire", in reference to this order of monks and the severe burning sensations in the limbs which was one of the symptoms.
There are two types of ergotism. The first is characterized by muscle spasms, fever and hallucinations and the victims may appear dazed, be unable to speak, become manic, or have other forms of paralysis or tremors, and suffer from hallucinations and other distorted perceptions. This is caused by serotonergic stimulation of the central nervous system by some of the alkaloids.
The second type of ergotism is marked by violent burning, absent peripheral pulses and shooting pain of the poorly vascularized distal organs, such as the fingers and toes, and are caused by effects of ergot alkaloids on the vascular system due to vasoconstriction, sometimes leading to gangrene and loss of limbs due to severely restricted blood circulation.
The psychoactive properties of the ergot alkaloids may also cause hallucinations and attendant irrational behaviour, convulsions, and even death. Other symptoms include strong uterine contractions, nausea, seizures, high fever, vomiting, loss of muscle strength and unconsciousness.
Since the Middle Ages, controlled doses of ergot were used to induce abortions and to stop maternal bleeding after childbirth.
Klotz offers a detailed overview of the toxicities in mammalian livestock, stating that the activities are attributable to antagonism or agonism of neurotransmitters, including dopamine, serotonin and norepinephrine. He also states that the adrenergic blockage by ergopeptines (e.g., ergovaline or ergotamine) leads to potent and long-term vasoconstriction, and can result in reduced blood flow resulting in intense burning pain (St. Anthony's fire), edema, cyanosis, dry gangrene and even loss of hooves in cattle or limbs in humans. Reduced prolactin due to ergot alkaloid activity on dopamine receptors in the pituitary is also common in livestock. Reduced serum prolactin is associated with various reproductive problems in cattle, and especially in horses, including agalactia and poor conception, and late-term losses of foals and sometimes mares due to dystocia and thickened placentas. Although both gangrenous and convulsive symptoms are seen in naturally occurring ergotism resulting from the ingestion of fungus infected rye, only gangrenous ergotism has been reported following the excessive ingestion of ergotamine tartrate.
Ergot extract has been used in pharmaceutical preparations, including ergot alkaloids in products such as Cafergot (containing caffeine and ergotamine or ergoline) to treat migraine headaches, and ergometrine, used to induce uterine contractions and to control bleeding after childbirth. Clinical ergotism as seen today results almost exclusively from the excessive intake of ergotamine tartrate in the treatment of migraine headache.
In addition to ergot alkaloids, Claviceps paspali also produces tremorgens (paspalitrem) causing "paspalum staggers" in cattle. The fungi of the genera Penicillium and Aspergillus also produce ergot alkaloids, notably some isolates of the human pathogen Aspergillus fumigatus, and have been isolated from plants in the family Convolvulaceae, of which morning glory is best known. The causative agents of most ergot poisonings are the ergot alkaloid class of fungal metabolites, though some ergot fungi produce distantly related indole-diterpene alkaloids that are tremorgenic.
Ergot does not contain lysergic acid diethylamide (LSD) but instead contains lysergic acid as well as its precursor, ergotamine. Lysergic acid is a precursor for the synthesis of LSD. Their realized and hypothesized medicinal uses have encouraged intensive research since the 1950s culminating on the one hand in development of drugs both legal (e.g., bromocriptine) and illegal (e.g., LSD), and on the other hand in extensive knowledge of the enzymes, genetics and diversity of ergot alkaloid biosynthetic pathways.
The January 4, 2007 issue of the New England Journal of Medicine includes a paper that documents a British study of more than 11,000 Parkinson's disease patients. The study found that two ergot-derived drugs, pergolide and cabergoline, commonly used to treat Parkinson's Disease may increase the risk of leaky heart valves by up to 700%.
Economic impact Ergot contamination of crops continues to have economic consequences. In the European Union, ergot in grains made for human consumption can only have 0.05% of ergot in grains and up to a maximum and selling grains with a higher percentage than that would result in fines and fees. Similar standards are held for the US and Canada. Additional costs also arise from the cleaning of grains containing ergot with it being estimated to be 2€/dt. Average contamination levels in Germany between 1995 and 2004 were relatively stable with it being at 0.11% w/w. Outbreaks have caused severe localized losses, in 1998 there was almost a total loss of rye crops in Germany. In 2005, in the US Midwest there was also a widespread amount of ergot that was reported to be found in barley crops. To reduce the risk of ergot infection found in grains, farmers have to introduce different methods such as changes in crop rotation and deeper ploughing.Haarmann, T., Rolke, Y., Giesbert, S., & Tudzynski, P. (2009, July). Ergot: From Witchcraft to Biotechnology. Molecular plant pathology. https://pmc.ncbi.nlm.nih.gov/articles/PMC6640538/