Department of Plant and Microbial Biology, The University of California, Berkeley, CA 94720.
Institut für Genetik, Technische Universität Braunschweig, 38106 Braunschweig, Germany.
Microbiol Spectr. 2017 Mar;5(2). doi: 10.1128/microbiolspec.FUNK-0015-2016.
For the majority of fungal species, the somatic body of an individual is a network of interconnected cells sharing a common cytoplasm and organelles. This syncytial organization contributes to an efficient distribution of resources, energy, and biochemical signals. Cell fusion is a fundamental process for fungal development, colony establishment, and habitat exploitation and can occur between hyphal cells of an individual colony or between colonies of genetically distinct individuals. One outcome of cell fusion is the establishment of a stable heterokaryon, culminating in benefits for each individual via shared resources or being of critical importance for the sexual or parasexual cycle of many fungal species. However, a second outcome of cell fusion between genetically distinct strains is formation of unstable heterokaryons and the induction of a programmed cell death reaction in the heterokaryotic cells. This reaction of nonself rejection, which is termed heterokaryon (or vegetative) incompatibility, is widespread in the fungal kingdom and acts as a defense mechanism against genome exploitation and mycoparasitism. Here, we review the currently identified molecular players involved in the process of somatic cell fusion and its regulation in filamentous fungi. Thereafter, we summarize the knowledge of the molecular determinants and mechanism of heterokaryon incompatibility and place this phenomenon in the broader context of biotropic interactions and immunity.
对于大多数真菌物种来说，个体的体细胞是一个由共享细胞质和细胞器的相互连接的细胞网络组成。这种合胞体组织有助于资源、能量和生化信号的有效分配。细胞融合是真菌发育、菌落建立和栖息地利用的基本过程，它可以发生在单个菌落的菌丝细胞之间，也可以发生在遗传上不同的个体之间。细胞融合的一个结果是建立一个稳定的异核体，通过共享资源为每个个体带来好处，或者对许多真菌物种的有性或准性周期至关重要。然而，遗传上不同菌株之间细胞融合的第二个结果是形成不稳定的异核体，并诱导异核细胞发生程序性细胞死亡反应。这种非自我排斥的反应，称为异核体（或营养体）不亲和性，在真菌界广泛存在，是一种抵御基因组利用和真菌寄生的防御机制。在这里，我们回顾了丝状真菌体细胞融合及其调控过程中涉及的目前已鉴定的分子参与者。此后，我们总结了异核体不亲和性的分子决定因素和机制的知识，并将这一现象置于生物相互作用和免疫的更广泛背景下。
