Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, 650201 Kunming, China.
Chinese Academy of Sciences Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, 100049 Beijing, China.
Proc Natl Acad Sci U S A. 2020 Sep 15;117(37):23125-23130. doi: 10.1073/pnas.2009445117. Epub 2020 Aug 31.
Many plants use environmental cues, including seasonal changes of day length (photoperiod), to control their flowering time. Under inductive conditions, FLOWERING LOCUS T (FT) protein is synthesized in leaves, and FT protein is a mobile signal, which is able to travel to the shoot apex to induce flowering. Dodders (, Convolvulaceae) are root- and leafless plants that parasitize a large number of autotrophic plant species with varying flowering time. Remarkably, some dodder species, e.g., , are able to synchronize their flowering with the flowering of their hosts. Detailed sequence inspection and expression analysis indicated that the gene in dodder very likely does not function in activating flowering. Using soybean host plants cultivated under inductive and noninductive photoperiod conditions and soybean and tobacco host plants, in which was overexpressed and knocked out, respectively, we show that FT-induced flowering of the host is likely required for both host and parasite flowering. Biochemical analysis revealed that host-synthesized FT signals are able to move into dodder stems, where they physically interact with a dodder FD transcription factor to activate dodder flowering. This study demonstrates that FTs can function as an important interplant flowering signal in host-dodder interactions. The unique means of flowering regulation of dodder illustrates how regressive evolution, commonly found in parasites, may facilitate the physiological synchronization of parasite and host, here allowing the parasite to time reproduction exactly with that of their hosts, likely optimizing parasite fitness.
许多植物利用环境线索，包括日照时间（光周期）的季节性变化，来控制其开花时间。在诱导条件下，FT 蛋白在叶片中合成，FT 蛋白是一种移动信号，能够移动到茎尖诱导开花。菟丝子（旋花科）是一种无根无叶的植物，寄生在大量具有不同开花时间的自养植物物种上。值得注意的是，一些菟丝子物种，例如，能够与它们的宿主同步开花。详细的序列检测和表达分析表明，菟丝子 中的 基因很可能不参与激活开花。利用在诱导和非诱导光周期条件下种植的大豆宿主植物，以及分别过表达和敲除 的大豆和烟草宿主植物，我们表明，FT 诱导的宿主开花可能是宿主和寄生虫开花所必需的。生化分析表明，宿主合成的 FT 信号能够进入菟丝子茎中，在那里与菟丝子 FD 转录因子相互作用，激活菟丝子开花。这项研究表明，FT 可以作为宿主-菟丝子相互作用中一种重要的植物间开花信号。菟丝子独特的开花调节方式说明了寄生中常见的退行进化如何促进寄生虫和宿主的生理同步，这里允许寄生虫与宿主的繁殖时间完全同步，可能优化了寄生虫的适应性。
