Yokoyama Toshiya, Asaoka Mariko, Nishitani Kazuhiko
Department of Science, Faculty of Science, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-Ku, Yokohama, Kanagawa, 221-8686, Japan.
J Plant Res. 2025 Jun 24. doi: 10.1007/s10265-025-01653-5.
Cuscuta, a genus of stem-parasitic plants, requires specific light and touch stimuli for host recognition and haustorium formation. Blue and far-red light promote parasitism, while red light inhibits it, but the roles played by light-responsive genes in the early stages of Cuscuta parasitism remain largely unexplored. This study utilized an in vitro C. campestris haustorium induction system to investigate this issue. RNA-sequence analysis revealed a group of differentially expressed genes that responded to the initiation of haustorium formation. Genes associated with light-signaling pathways, including phytochromes (PHYs), phytochrome-interacting factors (PIFs), and homeodomain-leucine zipper I/II transcription factors, were specifically up or downregulated in plants exposed to light for 4 h. Phylogenetic analysis demonstrated that two distinct forms of the PHYB gene, CcPHYB1 and CcPHYB2, were present in all sequenced Cuscuta species. CcPHYB2 was not expressed under normal light conditions, but was specifically upregulated under light regimes inducing haustorium formation; by contrast, CcPHYB1 exhibited non-light-dependent expression. Furthermore, the induction of haustorium formation by far-red light was canceled by red light exposure but could be re-activated by subsequent re-exposure to far-red light. The levels of expression of CcPHYB2, CcPIF1, CcPIF4, CcHOMEOBOX FROM ARABIDOPSIS THALIANA 3 (CcHAT3), CcHOMEOBOX 2 (CcHB2) and CcHB13 varied under different haustorium-inducing light conditions. Expression of these genes altered significantly upon exposure to blue and far-red light, but these changes were reversed in plants exposed to red light. These findings highlight the pivotal role of light-responsive signaling during the early stages of parasitism, providing valuable insights into the molecular mechanisms and evolution of light-mediated host recognition and parasitism in Cuscuta species.
菟丝子是一种茎寄生植物属，其宿主识别和吸器形成需要特定的光照和触碰刺激。蓝光和远红光促进寄生作用，而红光则抑制寄生作用，但光响应基因在菟丝子寄生早期所起的作用在很大程度上仍未得到探索。本研究利用体外的田野菟丝子吸器诱导系统来研究这个问题。RNA 序列分析揭示了一组对吸器形成起始有反应的差异表达基因。与光信号通路相关的基因，包括光敏色素（PHY）、光敏色素相互作用因子（PIF）和同源结构域 - 亮氨酸拉链 I/II 转录因子，在光照 4 小时的植物中特异性上调或下调。系统发育分析表明，在所有已测序的菟丝子物种中都存在两种不同形式的 PHYB 基因，即 CcPHYB1 和 CcPHYB2。CcPHYB2 在正常光照条件下不表达，但在诱导吸器形成的光照条件下特异性上调；相比之下，CcPHYB1 表现出非光依赖性表达。此外，远红光诱导的吸器形成在红光照射后被消除，但随后再次暴露于远红光可使其重新激活。在不同的吸器诱导光照条件下，CcPHYB2、CcPIF1、CcPIF4、拟南芥同源结构域 3（CcHAT3）、同源结构域 2（CcHB2）和 CcHB13 的表达水平有所不同。这些基因在暴露于蓝光和远红光时表达发生显著变化，但在暴露于红光的植物中这些变化被逆转。这些发现突出了光响应信号在寄生早期阶段的关键作用，为菟丝子物种中光介导的宿主识别和寄生的分子机制及进化提供了有价值的见解。
