Department of Plant Pathology, University of Arkansas Division of Agriculture, Fayetteville, Arkansas 72701, USA.
Mycologia. 2010 Nov-Dec;102(6):1221-8. doi: 10.3852/09-041. Epub 2010 Jul 13.
Many metabolic and developmental processes in fungi are controlled by biological rhythms. Circadian rhythms approximate a daily (24 h) cycle and have been thoroughly studied in the model fungus, Neurospora crassa. However relatively few examples of true circadian rhythms have been documented among other filamentous fungi. In this study we describe a circadian rhythm underlying hyphal melanization in Cercospora kikuchii, an important pathogen of soybean. After growth in light or light : dark cycles, colonies transferred to darkness produced zonate bands of melanized hyphae interspersed with bands of hyaline hyphae. Rhythmic production of bands was remarkably persistent in the absence of external cues, lasting at least 7 d after transfer to darkness, and was compensated over a range of temperatures. As in N. crassa, blue light but not red light was sufficient to entrain the circadian rhythm in C. kikuchii, and a putative ortholog of white collar-1, one of the genes required for light responses in N. crassa, was identified in C. kikuchii. Circadian regulation of melanization is conserved in other members of the genus: Similar rhythms were identified in another field isolate of C. kikuchii as well as field isolates of C. beticola and C. sorghi, but not in wild-type strains of C. zeae-maydis or C. zeina. This report represents the first documented circadian rhythm among Dothideomycete fungi and provides a new opportunity to dissect the molecular basis of circadian rhythms among filamentous fungi.
许多真菌的代谢和发育过程受生物节律控制。昼夜节律近似于每日（24 小时）周期，在模式真菌 Neurospora crassa 中得到了深入研究。然而，在其他丝状真菌中，真正的昼夜节律的例子相对较少。在这项研究中，我们描述了 Cercospora kikuchii 中菌丝黑化的昼夜节律，Cercospora kikuchii 是大豆的一种重要病原体。在光照或光照：黑暗循环中生长后，转移到黑暗中的菌落产生了有黑色素菌丝的带状区域，与透明菌丝的带状区域交错。在没有外部线索的情况下，带状物的周期性产生非常持久，在转移到黑暗后至少持续 7 天，并且在一系列温度下得到补偿。与 Neurospora crassa 一样，蓝光但不是红光足以使 C. kikuchii 的昼夜节律同步，并且在 C. kikuchii 中鉴定出了 white collar-1 的一个假定同源物，white collar-1 是 Neurospora crassa 中光反应所必需的基因之一。黑化的昼夜节律调节在该属的其他成员中是保守的：在另一个 C. kikuchii 的田间分离株以及 C. beticola 和 C. sorghi 的田间分离株中也鉴定出了类似的节律，但在 C. zeae-maydis 或 C. zeina 的野生型菌株中则没有。本报告代表了 Dothideomycete 真菌中第一个有记录的昼夜节律，并为解析丝状真菌中昼夜节律的分子基础提供了新的机会。
