Spore

In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa.[1] Bacterial spores are not part of a sexual cycle but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoebulae into their hosts for parasitic infection, but also reproduce within the hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula.[2]

Spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. Under favourable conditions the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, which eventually goes on to produce gametes. Two gametes fuse to form a zygote which develops into a new sporophyte. This cycle is known as alternation of generations.

The spores of seed plants are produced internally, and the megaspores (formed within the ovules) and the microspores are involved in the formation of more complex structures that form the dispersal units, the seeds and pollen grains.

Sporic meiosis
Spores produced in a sporic life cycle.
Brachythecium rutabulum on Populus x canadensis
Fresh snow partially covers rough-stalked feather-moss (Brachythecium rutabulum), growing on a thinned hybrid black poplar (Populus x canadensis). The last stage of the moss lifecycle is shown, where the sporophytes are visible before dispersion of their spores: the calyptra (1) is still attached to the capsule (2). The tops of the gametophytes (3) can be discerned as well. Inset shows the surrounding, black poplars growing on sandy loam on the bank of a kolk, with the detail area marked.

Definition

The term spore derives from the ancient Greek word σπορά spora, meaning "seed, sowing", related to σπόρος sporos, "sowing," and σπείρειν speirein, "to sow."

In common parlance, the difference between a "spore" and a "gamete" is that a spore will germinate and develop into a sporeling, while a gamete needs to combine with another gamete to form a zygote before developing further.

The main difference between spores and seeds as dispersal units is that spores are unicellular, the first cell of a gametophyte, while seeds contain within them a developing embryo (the multicellular sporophyte of the next generation), produced by the fusion of the male gamete of the pollen tube with the female gamete formed by the megagametophyte within the ovule. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes.

Classification of spore-producing organisms

Plants

Vascular plant spores are always haploid. Vascular plants are either homosporous (or isosporous) or heterosporous. Plants that are homosporous produce spores of the same size and type.

Heterosporous plants, such as seed plants, spikemosses, quillworts, and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male". Such plants typically give rise to the two kind of spores from within separate sporangia, either a megasporangium that produces megaspores or a microsporangium that produces microspores. In flowering plants, these sporangia occur within the carpel and anthers, respectively.

Fungi

Fungi commonly produce spores, as a result of sexual, or asexual, reproduction. Spores are usually haploid and grow into mature haploid individuals through mitotic division of cells (Urediniospores and Teliospores among rusts are dikaryotic). Dikaryotic cells result from the fusion of two haploid gamete cells. Among sporogenic dikaryotic cells, karyogamy (the fusion of the two haploid nuclei) occurs to produce a diploid cell. Diploid cells undergo meiosis to produce haploid spores.

Classification of spores

Spores can be classified in several ways:

By spore-producing structure

Microspore-formation
In plants, microspores, and in some cases megaspores, are formed from all four products of meiosis.
Macrospore-formation
In contrast, in many seed plants and heterosporous ferns, only a single product of meiosis will become a megaspore (macrospore), with the rest degenerating.

Fungi

In fungi and fungus-like organisms, spores are often classified by the structure in which meiosis and spore production occurs. Since fungi are often classified according to their spore-producing structures, these spores are often characteristic of a particular taxon of the fungi.

Red algae

By function

  • Chlamydospores: thick-walled resting spores of fungi produced to survive unfavorable conditions.
  • Parasitic fungal spores may be classified into internal spores, which germinate within the host, and external spores, also called environmental spores, released by the host to infest other hosts.[3]

By origin during life cycle

By mobility

Spores can be differentiated by whether they can move or not.

  • Zoospores: mobile spores that move by means of one or more flagella, and can be found in some algae and fungi.
  • Aplanospores: immobile spores that may nevertheless potentially grow flagella.
  • Autospores: immobile spores that cannot develop flagella.
  • Ballistospores: spores that are forcibly discharged or ejected from the fungal fruiting body as the result of an internal force, such as buildup of pressure. Most basidiospores are also ballistospores, and another notable example is spores of the genus Pilobolus.
  • Statismospores: spores that are discharged from the fungal fruiting body as the result of an external force, such as raindrops or a passing animal. Examples are puffballs.

Anatomy

Under high magnification, spores can be categorized as either monolete spores or trilete spores. In monolete spores, there is a single line on the spore indicating the axis on which the mother spore was split into four along a vertical axis. In trilete spores, all four spores share a common origin and are in contact with each other, so when they separate, each spore shows three lines radiating from a center pole.

Spore tetrads and trilete spores

Envelope-enclosed spore tetrads are taken as the earliest evidence of plant life on land,[4] dating from the mid-Ordovician (early Llanvirn, ~470 million years ago), a period from which no macrofossils have yet been recovered.[5] Individual trilete spores resembling those of modern cryptogamic plants first appeared in the fossil record at the end of the Ordovician period.[6]

Dispersal

Spores being ejected by fungi.

In fungi, both asexual and sexual spores or sporangiospores of many fungal species are actively dispersed by forcible ejection from their reproductive structures. This ejection ensures exit of the spores from the reproductive structures as well as travelling through the air over long distances. Many fungi thereby possess specialized mechanical and physiological mechanisms as well as spore-surface structures, such as hydrophobins, for spore ejection. These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolytes in the fluids of the ascus that lead to explosive discharge of the ascospores into the air.[7]

The forcible discharge of single spores termed ballistospores involves formation of a small drop of water (Buller's drop), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g.[8] Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs. Attracting insects, such as flies, to fruiting structures, by virtue of their having lively colours and a putrid odour, for dispersal of fungal spores is yet another strategy, most prominently used by the stinkhorns.

In Common Smoothcap moss (Atrichum undulatum), the vibration of sporophyte has been shown to be an important mechanism for spore release.[9]

In the case of spore-shedding vascular plants such as ferns, wind distribution of very light spores provides great capacity for dispersal. Also, spores are less subject to animal predation than seeds because they contain almost no food reserve; however they are more subject to fungal and bacterial predation. Their chief advantage is that, of all forms of progeny, spores require the least energy and materials to produce.

In the spikemoss Selaginella lepidophylla, dispersal is achieved in part by an unusual type of diaspore, a tumbleweed.[10]

Gallery

Bartramia ithyphylla sporen.jpeg

Spores of the moss Bartramia ithyphylla. (microscopic view, 400x)

Fernspore1

Dehisced fern sporangia. (microscopic view, no spores are visible)

Botbrush1

Spores and elaters from a horsetail. (Equisetum, microscopic view)

Trilete spores

Fossil plant spores (Scylaspora) from Silurian deposits of Sweden.

Unknown fruit mold with spores methylene blue x2000

Fruit mold with spores and distinguishable cellular growth. (2000x)

Reticularia olivacea-1

Spore clusters, formed inside sporangia of the slime mold Reticularia olivacea, from pine forests of eastern Ukraine.

Tubifera dudkae-4

Internal surface of the peridium of the slime mold Tubifera dudkae with spores.

See also

References

  1. ^ Tree Of Life Web Project
  2. ^ "Myxozoa". Tree of Life web project. Ivan Fiala 10 July 2008. Web. 14 Jan. 2014.
  3. ^ "Microsporidia (Protozoa): A Handbook of Biology and Research Techniques". Archived from the original on 26 June 2008. Retrieved 8 July 2007.CS1 maint: BOT: original-url status unknown (link). modares.ac.ir
  4. ^ Gray, J.; Chaloner, W. G.; Westoll, T. S. (1985). "The Microfossil Record of Early Land Plants: Advances in Understanding of Early Terrestrialization, 1970–1984". Philosophical Transactions of the Royal Society B. 309 (1138): 167–195. Bibcode:1985RSPTB.309..167G. doi:10.1098/rstb.1985.0077. JSTOR 2396358.
  5. ^ Wellman CH, Gray J (2000). "The microfossil record of early land plants". Philosophical Transactions of the Royal Society B. 355 (1398): 717–732. doi:10.1098/rstb.2000.0612. PMC 1692785. PMID 10905606.
  6. ^ Steemans, P.; Herisse, A. L.; Melvin, J.; Miller, M. A.; Paris, F.; Verniers, J.; Wellman, C. H. (2009). "Origin and Radiation of the Earliest Vascular Land Plants" (PDF). Science. 324 (5925): 353. Bibcode:2009Sci...324..353S. doi:10.1126/science.1169659. ISSN 0036-8075. PMID 19372423.
  7. ^ Trail F. (2007). "Fungal cannons: explosive spore discharge in the Ascomycota". FEMS Microbiology Letters. 276 (1): 12–8. doi:10.1111/j.1574-6968.2007.00900.x. PMID 17784861.
  8. ^ Pringle A, Patek SN, Fischer M, Stolze J, Money NP (2005). "The captured launch of a ballistospore". Mycologia. 97 (4): 866–71. doi:10.3852/mycologia.97.4.866. PMID 16457355.
  9. ^ Johansson, Lönnell, Sundberg and Hylander (2014) Release thresholds for moss spores: the importance of turbulence and sporophyte length. Journal of Ecology, n/a-n/a.
  10. ^ "False Rose of Jericho – Selaginella lepidophyllaFalse Rose of Jericho – Selaginella lepidophylla". Plant- and Flower guide. February 2009. Retrieved 1 February 2010.
Basidiospore

A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. Typically, four basidiospores develop on appendages from each basidium, out of these 2 are of one strain and other 2 of its opposite strain. In gills under a cap of one common species, there exist millions of basidia. Some gilled mushrooms in the order Agaricales have the ability to release billions of spores. The puffball fungus Calvatia gigantea has been calculated to produce about five trillion basidiospores. Most basidiospores are forcibly discharged, and are thus considered ballistospores. These spores serve as the main air dispersal units for the fungi. The spores are released during periods of high humidity and generally have a night-time or pre-dawn peak concentration in the atmosphere.When basidiospores encounter a favorable substrate, they may germinate, typically by forming hyphae. These hyphae grow outward from the original spore, forming an expanding circle of mycelium. The circular shape of a fungal colony explains the formation of fairy rings, and also the circular lesions of skin-infecting fungi that cause ringworm. Some basidiospores germinate repetitively by forming small spores instead of hyphae.

Basidium

A basidium (pl., basidia) is a microscopic sporangium (or spore-producing structure) found on the hymenophore of fruiting bodies of basidiomycete fungi which are also called tertiary mycellium, developed from secondary mycelium. Tertiary mycelium is highly coiled secondary mycelium, a dikaryon. The presence of basidia is one of the main characteristic features of the Basidiomycota. A basidium usually bears four sexual spores called basidiospores; occasionally the number may be two or even eight. In a typical basidium, each basidiospore is borne at the tip of a narrow prong or horn called a sterigma (pl. sterigmata), and is forcibly discharged upon maturity.

The word basidium literally means little pedestal, from the way in which the basidium supports the spores. However, some biologists suggest that the structure more closely resembles a club. An immature basidium is known as a basidiole.

Development of Spore

Spore is a video game developed by Maxis and designed by Will Wright, released in September 2008. The game has drawn wide attention for its ability to simulate the development of a species on a galactic scope, using its innovation of user-guided evolution via the use of procedural generation for many of the components of the game, providing vast scope and open-ended gameplay.

Spore is a god game. The player molds and guides a species across many generations, growing it from a single-celled organism into a more complex animal. Eventually, the species becomes sentient. The player then begins molding and guiding this species' society, developing it into a space-faring civilization, at which point they can explore the galaxy in a space ship. Spore's main innovation is the use of procedural generation for many of the components of the game, providing vast scope and open-endedness. Wright said, "I didn't want to make players feel like Luke Skywalker or Frodo Baggins. I wanted them to be like George Lucas or J. R. R. Tolkien." During the 2007 Technology Entertainment Design (TED) conference, Wright added that he wanted to create a "toy" for kids to inspire long-term thinking, stating, "I think toys can change the world."

Endospore

An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Firmicutes. The name "endospore" is suggestive of a spore or seed-like form (endo means within), but it is not a true spore (i.e., not an offspring). It is a stripped-down, dormant form to which the bacterium can reduce itself. Endospore formation is usually triggered by a lack of nutrients, and usually occurs in gram-positive bacteria. In endospore formation, the bacterium divides within its cell wall, and one side then engulfs the other. Endospores enable bacteria to lie dormant for extended periods, even centuries. There are many reports of spores remaining viable over 10,000 years, and revival of spores millions of years old has been claimed. There is one report of viable spores of Bacillus marismortui in salt crystals approximately 250 million years old. When the environment becomes more favorable, the endospore can reactivate itself to the vegetative state. Most types of bacteria cannot change to the endospore form. Examples of bacteria that can form endospores include Bacillus and Clostridium.The endospore consists of the bacterium's DNA, ribosomes and large amounts of dipicolinic acid. Dipicolinic acid is a spore-specific chemical that appears to help in the ability for endospores to maintain dormancy. This chemical accounts for up to 10% of the spore's dry weight.Endospores can survive without nutrients. They are resistant to ultraviolet radiation, desiccation, high temperature, extreme freezing and chemical disinfectants. Thermo-resistant endospores were first hypothesized by Ferdinand Cohn after studying Bacillus subtilis (pictured to the right) growth on cheese after boiling the cheese. His notion of spores being the reproductive mechanism for the growth was a large blow to the previous suggestions of spontaneous generation. Astrophysicist Steinn Sigurdsson said "There are viable bacterial spores that have been found that are 40 million years old on Earth – and we know they're very hardened to radiation." Common anti-bacterial agents that work by destroying vegetative cell walls do not affect endospores. Endospores are commonly found in soil and water, where they may survive for long periods of time. A variety of different microorganisms form "spores" or "cysts," but the endospores of low G+C gram-positive bacteria are by far the most resistant to harsh conditions.Some classes of bacteria can turn into exospores, also known as microbial cysts, instead of endospores. Exospores and endospores are two kinds of "hibernating" or dormant stages seen in some classes of microorganisms.

Gametophyte

A gametophyte () is one of the two alternating phases in the life cycle of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis.

Germination

Germination is the process by which an organism grows from a seed or similar structure. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. In addition, the growth of a sporeling from a spore, such as the spores of hyphae from fungal spores, is also germination. Thus, in a general sense, germination can be thought of as anything expanding into greater being from a small existence or germ.

Gleba

Gleba is the spore-bearing inner mass of certain fungi such as the puffball or stinkhorn.

The gleba is a solid mass of spores, generated within an enclosed area within the sporocarp. The continuous maturity of the sporogenous cells leave the spores behind as a powdery mass that can be easily blown away. The gleba may be sticky or it may be enclosed in a case (peridiole).It is a tissue usually found in an angiocarpous fruit-body, especially gasteromycetes. Angiocarpous fruit-bodies usually consist of fruit enclosed within a covering that does not form a part of itself; such as the filbert covered by its husk, or the acorn seated in its cupule. The presence of gleba can be found in earthballs and puffballs. The gleba consists of mycelium, and basidia and may also contain capillitium threads.Gleba found on the fruit body of species in the family Phallaceae is typically gelatinous, often fetid-smelling, and deliquescent (becoming liquid from the absorption of water). It is formed on the exterior face of the cap or the upper part of the fruit body. The foul smell helps to attract insects that help disperse the spores. Chemicals that contribute to the odor include methylmercaptan and hydrogen sulfide.

Hymenium

The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia (basidiomycetes) or paraphyses (ascomycetes). Cystidia are often important for microscopic identification. The subhymenium consists of the supportive hyphae from which the cells of the hymenium grow, beneath which is the hymenophoral trama, the hyphae that make up the mass of the hymenophore.

The position of the hymenium is traditionally the first characteristic used in the classification and identification of mushrooms. Below are some examples of the diverse types which exist among the macroscopic Basidiomycota and Ascomycota.

In agarics, the hymenium is on the vertical faces of the gills.

In boletes, it is in a spongy mass of downward-pointing tubes.

In puffballs, it is internal.

In stinkhorns, it develops internally and then is exposed in the form of a foul-smelling gel.

In cup fungi, it is on the concave surface of the cup.

In teeth fungi, it grows on the outside of tooth-like spines.

Maxis

Maxis is an American video game developer and a division of Electronic Arts (EA). The studio was founded in 1987 by Will Wright and Jeff Braun, and acquired by EA in 1997. Maxis is best known for its simulation games, including The Sims.

Maxis' Emeryville studio was closed in March 2015, moving development of Maxis titles to other EA studio locations. Employees of the Emeryville studio were "given opportunities to explore" other positions within Maxis and other EA studios. In an organisational restructure later in September, the now consolidated Maxis team was moved to function alongside EA Mobile.

Milky spore

Paenibacillus popilliae (formerly Bacillus popilliae) is a soil-dwelling, Gram-positive, rod-shaped bacterium. It is responsible for a disease (commonly called milky spore) of the white grubs of Japanese beetles.

The adult Japanese beetles pupate in July (in the Northeast United States) and feed on flowers and leaves of shrubs and garden plants. During this adult stage, the beetles also mate and the females lay eggs in the soil in late July to early August. The eggs hatch soon afterwards and in this larval or grub stage, they feed on the roots of grass and other plants. As the weather gets cooler and winter approaches, the grubs go deeper into the soil, and feeding declines as they over-winter.

In August, when the grubs are close to the surface and feeding, they are vulnerable to infestation by milky spore. This is also the optimal time frame for turf inoculation or applications with milky spore to increase milky spore in the soil environment (there are product specific guidelines that should be followed for milky spore application).

Resident spores in the soil are swallowed by grubs during their normal pattern of feeding on roots. This ingestion of the spore by the host activates reproduction of the bacteria inside the grub. Within 7–21 days the grub will eventually die and as the grub decomposes, billions of new spores are released into the soil.

Milky spore in the soil is not harmful to beneficial insects, birds, bees, pets, or people; and milky spore, like other bacteria, is highly survivable in drought conditions but suffers in temperatures of Zone 5 and colder.

Pileus (mycology)

The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp (fungal fruiting body) that supports a spore-bearing surface, the hymenium. The hymenium (hymenophore) may consist of lamellae, tubes, or teeth, on the underside of the pileus. A pileus is characteristic of agarics, boletes, some polypores, tooth fungi, and some ascomycetes.

Rust (fungus)

Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales (previously also known as Uredinales).

An estimated 168 rust genera and approximately 7,000 species, more than half of which belong to the genus Puccinia, are currently accepted. Rust fungi are highly specialized plant pathogens with several unique features. Taken as a group, rust fungi are diverse and affect many kinds of plants. However, each species has a very narrow range of hosts and cannot be transmitted to non-host plants. In addition, most rust fungi cannot be grown easily in pure culture.

A single species of rust fungi may be able to infect two different plant hosts in different stages of its life cycle, and may produce up to five morphologically and cytologically distinct spore-producing structures viz., spermogonia, aecia, uredinia, telia, and basidia in successive stages of reproduction. Each spore type is very host specific, and can typically infect only one kind of plant.

Rust fungi are obligate plant pathogens that only infect living plants. Infections begin when a spore lands on the plant surface, germinates, and invades its host. Infection is limited to plant parts such as leaves, petioles, tender shoots, stem, fruits, etc. Plants with severe rust infection may appear stunted, chlorotic (yellowed), or may display signs of infection such as rust fruiting bodies. Rust fungi grow intracellularly, and make spore-producing fruiting bodies within or, more often, on the surfaces of affected plant parts. Some rust species form perennial systemic infections that may cause plant deformities such as growth retardation, witch's broom, stem canker, galls, or hypertrophy of affected plant parts.

Rusts get their name because they are most commonly observed as deposits of powdery rust-coloured or brown spores on plant surfaces. The Roman agricultural festival Robigalia (April 25) has ancient origins in combating wheat rust.

Spore (2008 video game)

Spore is a 2008 life simulation real-time strategy God game developed by Maxis Emeryville, published by Electronic Arts and designed by Will Wright, and was released for Microsoft Windows and Mac OS X. Covering many genres including action, real-time strategy, and role-playing games, Spore allows a player to control the development of a species from its beginnings as a microscopic organism, through development as an intelligent and social creature, to interstellar exploration as a spacefaring culture. It has drawn wide attention for its massive scope, and its use of open-ended gameplay and procedural generation. Throughout each stage, players are able to use various creators to produce content for their games. These are then automatically uploaded to the online Sporepedia and are accessible by other players for download.

Spore was released after several delays to generally favorable reviews. Praise was given for the fact that the game allowed players to create customized creatures, vehicles and buildings. However, Spore was criticized for its gameplay which was seen as shallow by many reviewers; GameSpot remarked: "Individual gameplay elements are extremely simple". Controversy surrounded Spore due to the inclusion of SecuROM, and its digital rights management software, which can potentially open the user's computer to security risks.

Spore photoproduct lyase

Spore photoproduct lyase (EC 4.1.99.14, SAM, SP lyase, SPL, SplB, SplG) is a radical SAM enzyme that repairs a particular kind of lesion that arises upon UV-radiation of bacterial DNA. This repair mechanism is one of the reasons for the resilience of certain bacterial spores. Through a series of radical reactions the photodimer, 3 5-thyminyl-5,6-dihydrothymine, is disconnected to give back two functional thymine rings.

Spore print

The spore print is the powdery deposit obtained by allowing spores of a fungal fruit body to fall onto a surface underneath. It is an important diagnostic character in most handbooks for identifying mushrooms. It shows the color of the mushroom spores if viewed en masse.

Zoospore

A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria and fungi to propagate themselves.

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