Marek Stephen M, Wu Jennifer, Louise Glass N, Gilchrist David G, Bostock Richard M
Department of Plant Pathology, University of California, Davis, CA 95616, USA.
Fungal Genet Biol. 2003 Nov;40(2):126-37. doi: 10.1016/s1087-1845(03)00086-0.
Many filamentous fungi are capable of undergoing conspecific hyphal fusion with a genetically different individual to form a heterokaryon. However, the viability of such heterokaryons is dependent upon vegetative (heterokaryon) incompatibility (het) loci. If two individuals undergo hyphal anastomosis, but differ in allelic specificity at one or more het loci, the fusion cell is usually compartmentalized and self-destructs. Many of the microscopic features associated with vegetative incompatibility resemble apoptosis in metazoans and plants. To test the hypothesis whether vegetative incompatibility results in nuclear degradation, a characteristic of apoptosis, the cytology of hyphal fusions between incompatible Neurospora crassa strains that differed at three het loci, mat, het-c and het-6, and the cytology of transformants containing incompatible het-c alleles were examined using fluorescent DNA stains and terminal deoxynucleotidyl transferase-mediated dUTP-X nick end labeling (TUNEL). Hyphal fusion cells between het incompatible strains and hyphal segments in het-c incompatible transformants were compartmentalized by septal plugging and contained heavily degraded nuclear DNA. Hyphal fusion cells in compatible self-pairings and hyphal cells in het-c compatible transformants were not compartmentalized and rarely showed TUNEL-positive nuclei. Cell death events also were observed in senescent, older hyphae. Morphological features of hyphal compartmentation and death during vegetative incompatibility and the extent to which it is genetically controlled can best be described as a form of programmed cell death.
许多丝状真菌能够与基因不同的个体进行同种菌丝融合，形成异核体。然而，这种异核体的活力取决于营养体（异核体）不亲和性（het）位点。如果两个个体进行菌丝吻合，但在一个或多个het位点的等位基因特异性上存在差异，融合细胞通常会被分隔并自我毁灭。许多与营养体不亲和性相关的微观特征类似于后生动物和植物中的细胞凋亡。为了检验营养体不亲和性是否导致细胞核降解（细胞凋亡的一个特征）这一假设，使用荧光DNA染色和末端脱氧核苷酸转移酶介导的dUTP-X缺口末端标记（TUNEL）技术，研究了在mat、het-c和het-6这三个het位点存在差异的不亲和粗糙脉孢菌菌株之间菌丝融合的细胞学，以及含有不兼容het-c等位基因的转化体的细胞学。不亲和菌株之间的菌丝融合细胞和het-c不兼容转化体中的菌丝片段通过隔膜堵塞进行分隔，并含有严重降解的核DNA。兼容自配对中的菌丝融合细胞和het-c兼容转化体中的菌丝细胞没有被分隔，很少显示TUNEL阳性细胞核。在衰老的、较老的菌丝中也观察到了细胞死亡事件。营养体不亲和期间菌丝分隔和死亡的形态特征以及其受遗传控制的程度，最好被描述为一种程序性细胞死亡形式。
