A bstractParasitic 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 H2O2 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.

中文翻译：

---

寄生被子植物中的信号器官发生：异种素生成、感知和反应

摘要 被子植物内的寄生策略通常通过在称为异种异种的过程中将发育转变与宿主识别信号紧密结合而取得成功。在玄参科中，就宿主识别过程而言，独脚金是研究最多和最了解的寄生成员之一。特定的异种素调节种子萌发、宿主附着器官的发育、吸器以及宿主-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的关键营养/寄生过渡。我们提供了独脚金根尖局部产生 H2O2 的证据，并建议如何使用这种氧化剂来利用宿主过氧化物酶和细胞壁果胶来产生简单的苯醌信号。事实证明，这种苯醌异种素对于培养的幼苗中的吸器诱导是必要的和充分的。此外，有证据表明苯醌与氧化还原活性位点结合完成了“氧化还原回路”以介导信号感知。这种氧化还原反应调节对成熟宿主附着器官发育至关重要的特定标记基因的时间依赖性表达。