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Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually; [1] i.e., having male and female reproductive structures on the same thallus. The opposite sexual functions are performed by different cells of a single mycelium. [2] It can be contrasted to heterothallic. It is often used to categorize fungi.
Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi , which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.
In consumer theory, a consumer's preferences are called homothetic if they can be represented by a utility function which is homogeneous of degree 1. [1]: 146 For example, in an economy with two goods ,, homothetic preferences can be represented by a utility function that has the following property: for every >:
Homothallic species are able to mate with themselves, while in heterothallic species only isolates of opposite mating types can mate. Mating between isogamous fungi may consist only of a transfer of a nucleus from one cell to another. Vegetative incompatibility within species often prevents a fungal isolate from mating with another isolate.
Those fungi that need a partner to mate are referred to as heterothallic (self-sterile), and those fungi not needing a partner are referred to as homothallic (self-fertile). A study of DNA sequences of mating type loci from different heterothallic and homothallic species in the genus Cochliobolus suggests that homothallism can be derived from ...
In heterothallic species, sexual reproduction occurs when opposite mating types (designated + and -) come into close proximity, inducing the formation of specialized hyphae called gametangia. The gametangia grow toward each other, then fuse, forming a diploid zygote at the point of fusion.
These are outcrossing (in heterothallic fungi) in which two different individuals contribute nuclei, and self-fertilization or selfing (in homothallic fungi) in which both nuclei are derived from the same individual. In recent years, sexual cycles have been discovered in numerous species previously thought to be asexual.
These fungi are said to be homothallic, versus the normal heterothallic species with mating types. Others are secondarily homothallic, in that two compatible nuclei following meiosis migrate into each basidiospore, which is then dispersed as a pre-existing dikaryon. Often such species form only two spores per basidium, but that too varies.