n nnnTo gain entry to plants, many pathogenic fungi develop specializedinfection structures called appressoria. Here, we demonstratethat appressorium morphogenesis in the rice blast fungus Magnaportheoryzae is tightly regulated by the cell cycle. Shortly aftera fungus spore lands on the rice (Oryza sativa) leaf surface,a single round of mitosis always occurs in the germ tube. Wefound that initiation of infection structure development isregulated by a DNA replication-dependent checkpoint. Geneticintervention in DNA synthesis, by conditional mutation of theNever-in-Mitosis 1 gene, prevented germ tubes from developingnascent infection structures. Cellular differentiation of appressoria,however, required entry into mitosis because nimA temperature-sensitivemutants, blocked at mitotic entry, were unable to develop functionalappressoria. Arresting the cell cycle after mitotic entry, byconditional inactivation of the Blocked-in-Mitosis 1 gene orexpression of stabilized cyclinB-encoding alleles, did not impairappressorium differentiation, but instead prevented these cellsfrom invading plant tissue. When considered together, thesedata suggest that appressorium-mediated plant infection is coordinatedby three distinct cell cycle checkpoints that are necessaryfor establishment of plant disease.展开▼
机译：ABSTRACTn n
n TOP n <字体颜色= 464c53>抽象 n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n n nnn要进入植物，许多致病真菌会开发专门的 i感染结构称为Appressoria。在这里，我们证明 稻瘟病菌 Magnaporthe oryzae 中的包皮形态发生受细胞周期的严格调控。 真菌孢子落在水稻（ Oryza sativa ）叶表面后不久， 胚芽管中总是发生单轮有丝分裂。我们 发现感染结构发育的启动受DNA复制依赖性检查点的调节。通过 Never-in-Mitosis 1基因的条件突变，遗传干预DNA合成中的 阻止了胚管发育 新生的感染结构。然而，食欲细胞的细胞分化 需要进入有丝分裂，因为在有丝分裂进入中受阻的 nimA 温度敏感型 突变体无法发育功能性< SUP> appressoria。通过 有条件的失活有丝分裂阻断1基因或 表达稳定的cyclinB编码等位基因，阻止有丝分裂进入细胞周期，不会损害 < / SUP> appressorium分化，但阻止了这些细胞 入侵植物组织。一起考虑时，这些 数据表明，食堂介导的植物感染通过三个不同的细胞周期检查点来协调 ，这三个点对于确定植物病害是必需的。展开▼
