The Department of Plant Biology, University of California, Davis, California 95616, USA.
RIKEN BioResource Research Center, Tsukuba, Ibaraki 305-0074, Japan.
Plant Physiol. 2021 Aug 3;186(4):2093-2110. doi: 10.1093/plphys/kiab231.
Parasitic plants reduce crop yield worldwide. Dodder (Cuscuta campestris) is a stem parasite that attaches to its host, using haustoria to extract nutrients and water. We analyzed the transcriptome of six C. campestris tissues and identified a key gene, LATERAL ORGAN BOUNDARIES DOMAIN 25 (CcLBD25), as highly expressed in prehaustoria and haustoria. Gene coexpression networks from different tissue types and laser-capture microdissection RNA-sequencing data indicated that CcLBD25 could be essential for regulating cell wall loosening and organogenesis. We employed host-induced gene silencing by generating transgenic tomato (Solanum lycopersicum) hosts that express hairpin RNAs to target and down-regulate CcLBD25 in the parasite. Our results showed that C. campestris growing on CcLBD25 RNAi transgenic tomatoes transited to the flowering stage earlier and had reduced biomass compared with C. campestris growing on wild-type (WT) hosts, suggesting that parasites growing on transgenic plants were stressed due to insufficient nutrient acquisition. We developed an in vitro haustorium system to assay the number of prehaustoria produced on strands from C. campestris. Cuscuta campestris grown on CcLBD25 RNAi tomatoes produced fewer prehaustoria than those grown on WT tomatoes, indicating that down-regulating CcLBD25 may affect haustorium initiation. Cuscuta campestris haustoria growing on CcLBD25 RNAi tomatoes exhibited reduced pectin digestion and lacked searching hyphae, which interfered with haustorium penetration and formation of vascular connections. The results of this study elucidate the role of CcLBD25 in haustorium development and might contribute to developing parasite-resistant crops.
寄生植物会降低全球作物的产量。菟丝子（Cuscuta campestris）是一种茎寄生植物，它通过附着在宿主植物上，利用吸器来提取营养和水分。我们分析了 6 种菟丝子组织的转录组，鉴定出一个关键基因，即侧生器官边界域 25（CcLBD25），它在预吸器和吸器中高度表达。来自不同组织类型的基因共表达网络和激光捕获显微切割 RNA-seq 数据表明，CcLBD25 可能对调节细胞壁松弛和器官发生至关重要。我们通过生成表达发夹 RNA 的转基因番茄（Solanum lycopersicum）宿主，对其进行寄主诱导基因沉默，以靶向和下调寄生物中的 CcLBD25。我们的结果表明，与在野生型（WT）宿主上生长的菟丝子相比，在 CcLBD25 RNAi 转基因番茄上生长的菟丝子更早地进入开花阶段，生物量也减少了，这表明由于养分获取不足，寄生在转基因植物上的菟丝子受到了压力。我们开发了一种体外吸器系统，以检测菟丝子的吸器前体在丝状体上产生的数量。与在 WT 番茄上生长的菟丝子相比，在 CcLBD25 RNAi 番茄上生长的菟丝子产生的吸器前体数量更少，这表明下调 CcLBD25 可能会影响吸器的起始。在 CcLBD25 RNAi 番茄上生长的菟丝子吸器表现出果胶消化减少，并且缺乏搜索菌丝，这干扰了吸器的穿透和血管连接的形成。这项研究的结果阐明了 CcLBD25 在吸器发育中的作用，并可能有助于开发抗寄生作物。
