The Spitzenkörper (

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

for 'pointed body', SPK) is a structure found in fungal

hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

that is the organizing center for hyphal growth and

morphogenesis Morphogenesis (from the Greek ''morphê'' shape and ''genesis'' creation, literally "the generation of form") is the biological process that causes a cell, tissue or organism to develop its shape. It is one of three fundamental aspects of deve ...

. It consists of many small vesicles and is present in growing hyphal tips, during spore

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, ...

, and where branch formation occurs. Its position in the hyphal tip correlates with the direction of hyphal growth. The Spitzenkörper is a part of the

endomembrane system The endomembrane system is composed of the different membranes (endomembranes) that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryote ...

in fungi. The vesicles are organized around a central area that contains a dense meshwork of

microfilament Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other ...

Polysome A polyribosome (or polysome or ergosome) is a group of ribosomes bound to an mRNA molecule like “beads” on a “thread”. It consists of a complex of an mRNA molecule and two or more ribosomes that act to translate mRNA instructions into p ...

s are often found closely to the posterior boundary of the Spitzenkörper core within the ''

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

'',

microtubules Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

extend into and often through the Spitzenkörper and within the Ascomycota Woronin bodies are found in the apical region near the Spitzenkörper. The

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

of the extreme apex is occupied almost exclusively by secretory vesicles. In the higher fungi (

and

Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

), secretory and endocytic vesicles are arranged into a dense, spherical aggregation called the Spitzenkörper or ‘apical body’. The Spitzenkörper may be seen in growing hyphae even with a light microscope. Hyphae of the Oomycota and some lower Eumycota (notably the

Zygomycota Zygomycota, or zygote fungi, is a former phylum, division or phylum of the kingdom Fungi. The members are now part of two Phylum, phyla: the Mucoromycota and Zoopagomycotina, Zoopagomycota. Approximately 1060 species are known. They are mostly t ...

) do not contain a recognizable Spitzenkörper, and the vesicles are instead distributed more loosely often in a crescent-shaped arrangement beneath the apical

plasma membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

. This structure is most commonly found in

Dikarya Dikarya is a subkingdom of Fungi that includes the divisions Ascomycota and Basidiomycota, both of which in general produce dikaryons, may be hypha, filamentous or unicellular, but are always without flagella. The Dikarya are most of the so-calle ...

and was at first thought to only occur among them. . Vargas et al 1993 however were the first to find a Spitzenkörper in another clade, specifically the

Allomyces ''Allomyces'' is a genus of fungi in the family Blastocladiaceae. It was circumscribed by British mycologist Edwin John Butler in 1911. Species in the genus have a polycentric thallus and reproduce sexually or asexually by zoospores that have ...

(

Blastocladiomycota Blastocladiomycota is one of the currently recognized phyla within the kingdom Fungi.Hibbett DS et al. 2007. A higher-level phylogenetic classification of the fungi. Mycological Research 111:509–47. Blastocladiomycota was originally the order ...

), then subsequently ''

Basidiobolus ranarum ''Basidiobolus'' is a fungus genus. It was circumscribed by the mycologist in 1886, with '' Basidiobolus ranarum'' assigned as the type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''spe ...

'' which has been placed in several different phyla was also found to have an SPK. these and the Blastocladiella (also in Blastocladiomycota) are the only known taxa to bear this structure.

References

Cell biology Fungal morphology and anatomy Articles containing video clips {{mycology-stub