Keyes WJ, O'Malley RC, Kim D, Lynn DG
Searle and Jones Chemistry Laboratory, 5735 Ellis Avenue, The University of Chicago, Chicago, IL 60637, USA
J Plant Growth Regul. 2000 Jun;19(2):217-231. doi: 10.1007/s003440000024.
Parasitic strategies within the angiosperms generally succeed by tightly coupling developmental transitions with host recognition signals in a process referred to as xenognosis. Within the Scrophulariaceae, Striga asiatica is among the most studied and best understood parasitic member with respect to the processes of host recognition. Specific xenognosins regulate seed germination, the development of the host attachment organ, the haustorium, and several later stages of host-parasite integration. Here we discuss the signals regulating the development of the haustorium, the critical vegetative/parasitic transition in the life cycle of this obligate parasite. We provide evidence for the localized production of H(2)O(2) at the Striga root tip and suggest how this oxidant is used to exploit host peroxidases and cell wall pectins to generate a simple benzoquinone signal. This benzoquinone xenognosin proves to be both necessary and sufficient for haustorial induction in cultured seedlings. Furthermore, evidence is provided that benzoquinone binding to a redox active site completes a "redox circuit" to mediate signal perception. This redox reaction regulates the time-dependent expression of specific marker genes critical for the development of the mature host attachment organ. These studies extend the emerging series of events necessary for the molecular regulation of organogenesis within the parasitic plants and suggest novel signaling features and molecular mechanisms that may be common across higher plants.
被子植物中的寄生策略通常通过在一个被称为异源识别的过程中将发育转变与宿主识别信号紧密耦合来成功实现。在玄参科中，就宿主识别过程而言，亚洲独脚金是研究最多且理解最透彻的寄生成员之一。特定的异源识别素调节种子萌发、宿主附着器官（吸器）的发育以及宿主 - 寄生虫整合的几个后期阶段。在这里，我们讨论调节吸器发育的信号，这是这种专性寄生虫生命周期中关键的营养/寄生转变。我们提供了亚洲独脚金根尖局部产生过氧化氢的证据，并提出这种氧化剂如何被用来利用宿主过氧化物酶和细胞壁果胶来产生一种简单的苯醌信号。这种苯醌异源识别素被证明对于培养幼苗中的吸器诱导既是必要的也是充分的。此外，有证据表明苯醌与一个氧化还原活性位点结合完成了一个“氧化还原回路”以介导信号感知。这种氧化还原反应调节特定标记基因的时间依赖性表达，这些基因对于成熟宿主附着器官的发育至关重要。这些研究扩展了寄生植物中器官发生分子调控所需的一系列新出现的事件，并提出了可能在高等植物中普遍存在的新信号特征和分子机制。
