Salgado Marco Guedes, Maity Pooja Jha, Lundin Daniel, Pawlowski Katharina
Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
PLoS One. 2025 Feb 3;20(2):e0315798. doi: 10.1371/journal.pone.0315798. eCollection 2025.
All nitrogen-fixing root nodule symbioses of angiosperms-legume and actinorhizal symbioses-possess a common ancestor. Molecular processes for the induction of root nodules are modulated by phytohormones, as is the case of the first nodulation-related transcription factor NODULE INCEPTION (NIN), whose expression can be induced by exogenous cytokinin in legumes. The process of actinorhizal nodule organogenesis is less well understood. To study the changes exerted by phytohormones on the expression of the orthologs of CYCLOPS, NIN, and NF-YA1 in the actinorhizal host Datisca glomerata, an axenic hydroponic system was established and used to examine the transcriptional responses (RT-qPCR) in roots treated with the synthetic cytokinin 6-Benzylaminopurine (BAP), the natural auxin Phenylacetic acid (PAA), and the synthetic auxin 1-Naphthaleneacetic acid (NAA). The model legume Lotus japonicus was used as positive control. Molecular readouts for auxins and cytokinin were established: DgSAUR1 for PAA, DgGH3.1. for NAA, and DgARR9 for BAP. L. japonicus NIN was induced by BAP, PAA, and NAA in a dosage- and time-dependent manner. While expression of D. glomerata NIN2 could not be induced in roots, D. glomerata NIN1 was induced by PAA; this induction was abolished in the presence of exogenous BAP. Furthermore, the induction of DgNIN1 expression by PAA required ethylene and gibberellic acid. This study suggests that while cytokinin signaling is central for cortex-induced nodules of L. japonicus, it acts antagonistically to the induction of nodule primordia of D. glomerata by PAA in the root pericycle.
被子植物的所有固氮根瘤共生体——豆科植物和放线菌根共生体——都有一个共同的祖先。根瘤诱导的分子过程受植物激素调控，首个与结瘤相关的转录因子“结瘤起始”（NIN）就是如此，其表达可被豆科植物中的外源细胞分裂素诱导。放线菌根瘤器官发生的过程尚不太清楚。为了研究植物激素对放线菌根宿主聚花 Datisca 中 CYCLOPS、NIN 和 NF-YA1 直系同源基因表达的影响，建立了一个无菌水培系统，用于检测用合成细胞分裂素 6-苄基腺嘌呤（BAP）、天然生长素苯乙酸（PAA）和合成生长素 1-萘乙酸（NAA）处理的根中的转录反应（RT-qPCR）。模式豆科植物日本百脉根用作阳性对照。建立了生长素和细胞分裂素的分子读数：PAA 对应的 DgSAUR1、NAA 对应的 DgGH3.1 和 BAP 对应的 DgARR9。日本百脉根的 NIN 被 BAP、PAA 和 NAA 以剂量和时间依赖性方式诱导。虽然聚花 Datisca 的 NIN2 在根中不能被诱导表达，但聚花 Datisca 的 NIN1 被 PAA 诱导；在外源 BAP 存在的情况下，这种诱导作用被消除。此外，PAA 对 DgNIN1 表达的诱导需要乙烯和赤霉素。这项研究表明，虽然细胞分裂素信号传导对于日本百脉根皮层诱导的根瘤至关重要，但它在根中柱鞘中对 PAA 诱导聚花 Datisca 的根瘤原基起拮抗作用。
