Data from: Nod factors potentiate auxin signaling for transcriptional regulation and lateral root formation in Medicago truncatula

Nodulation (Nod) factors (NFs) are symbiotic molecules produced by rhizobia that are essential for establishment of the rhizobium–legume endosymbiosis. Purified NFs can stimulate lateral root formation (LRF) in Medicago truncatula, but little is known about the molecular mechanisms involved. Using a combination of reporter constructs, pharmacological and genetic approaches, we show that NFs act on early steps of LRF in M. truncatula, independently of the ethylene signaling pathway and of the cytokinin receptor MtCRE1, but in interaction with auxin. We conducted a whole-genome transcriptomic study upon NF and/or auxin treatments, using a lateral root inducible system adapted for M. truncatula. This revealed a large overlap between NF and auxin signaling and, more interestingly, synergistic interactions between these molecules. Three groups showing interaction effects were defined: group 1 contained more than 1500 genes responding specifically to the combinatorial treatment of NFs and auxin; group 2 comprised auxin-regulated genes whose expression was enhanced or antagonized by NFs; and in group 3 the expression of NF regulated genes was antagonized by auxin. Groups 1 and 2 were enriched in signaling and metabolic functions, which highlights important crosstalk between NF and auxin signaling for both developmental and symbiotic processes.

结瘤因子（Nodulation factors, NFs）是根瘤菌产生的共生分子，对根瘤菌-豆科植物内共生体系的建立至关重要。纯化的结瘤因子可刺激蒺藜苜蓿（Medicago truncatula）的侧根发生（lateral root formation, LRF），但目前对其背后的分子机制尚不明晰。本研究结合报告基因构建体、药理学与遗传学研究手段，证实结瘤因子可作用于蒺藜苜蓿侧根发生的早期阶段，该过程不依赖乙烯信号通路与细胞分裂素受体MtCRE1，但需与生长素协同发挥作用。我们采用适配蒺藜苜蓿的侧根诱导系统，针对结瘤因子和/或生长素处理开展了全基因组转录组学分析。结果显示，结瘤因子与生长素的信号通路存在大量重叠，更值得关注的是二者间存在协同相互作用。本研究将受调控基因划分为三类具有交互效应的基因簇：第1类包含超过1500个仅在结瘤因子与生长素联合处理下产生表达响应的基因；第2类包含受生长素调控的基因，其表达可被结瘤因子增强或拮抗；第3类则包含受结瘤因子调控的基因，其表达可被生长素拮抗。第1类与第2类基因富集于信号转导与代谢功能通路，这表明结瘤因子与生长素的信号串扰在植物发育与共生过程中均发挥关键作用。