Cui Songkui, Wakatake Takanori, Hashimoto Kei, Saucet Simon B, Toyooka Kiminori, Yoshida Satoko, Shirasu Ken
RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-045, Japan (S.C., T.W., K.H., S.B.S., K.T., S.Y., K.S.); andGraduate School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan (T.W., K.S.).
RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-045, Japan (S.C., T.W., K.H., S.B.S., K.T., S.Y., K.S.); andGraduate School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan (T.W., K.S.)
Plant Physiol. 2016 Mar;170(3):1492-503. doi: 10.1104/pp.15.01786. Epub 2015 Dec 28.
A haustorium is the unique organ that invades host tissues and establishes vascular connections. Haustorium formation is a key event in parasitism, but its underlying molecular basis is largely unknown. Here, we use Phtheirospermum japonicum, a facultative root parasite in the Orobanchaceae, as a model parasitic plant. We performed a forward genetic screen to identify mutants with altered haustorial morphologies. The development of the haustorium in P. japonicum is induced by host-derived compounds such as 2,6-dimethoxy-p-benzoquinone. After receiving the signal, the parasite root starts to swell to develop a haustorium, and haustorial hairs proliferate to densely cover the haustorium surface. We isolated mutants that show defects in haustorial hair formation and named them haustorial hair defective (hhd) mutants. The hhd mutants are also defective in root hair formation, indicating that haustorial hair formation is controlled by the root hair development program. The internal structures of the haustoria in the hhd mutants are similar to those of the wild type, indicating that the haustorial hairs are not essential for host invasion. However, all the hhd mutants form fewer haustoria than the wild type upon infection of the host roots. The number of haustoria is restored when the host and parasite roots are forced to grow closely together, suggesting that the haustorial hairs play a role in stabilizing the host-parasite association. Thus, our study provides genetic evidence for the regulation and function of haustorial hairs in the parasitic plant.
吸器是侵入宿主组织并建立维管连接的独特器官。吸器形成是寄生过程中的关键事件，但其潜在的分子基础 largely unknown。在这里，我们使用列当科的兼性根寄生植物日本列当作为模式寄生植物。我们进行了正向遗传学筛选，以鉴定吸器形态发生改变的突变体。日本列当吸器的发育由宿主衍生的化合物如2,6-二甲氧基对苯醌诱导。接收到信号后，寄生根开始肿胀以发育出吸器，吸器毛大量增殖以密集覆盖吸器表面。我们分离出了在吸器毛形成方面存在缺陷的突变体，并将它们命名为吸器毛缺陷（hhd）突变体。hhd突变体在根毛形成方面也存在缺陷，这表明吸器毛的形成受根毛发育程序控制。hhd突变体吸器的内部结构与野生型相似，这表明吸器毛对于侵入宿主并非必不可少。然而，在感染宿主根时，所有hhd突变体形成的吸器都比野生型少。当宿主根和寄生根被迫紧密生长在一起时，吸器的数量得以恢复，这表明吸器毛在稳定宿主 - 寄生关系中发挥作用。因此，我们的研究为寄生植物中吸器毛的调控和功能提供了遗传学证据。
