Drought, bringing the risks of agricultural production losses, is becoming a globally environmental stress. Previous results suggested that legumes with nodules exhibited superior drought tolerance compared with the non-nodule group. To investigate the molecular mechanism of rhizobium symbiosis impacting drought tolerance, transcriptome and sRNAome sequencing were performed to identify the potential mRNA–miRNA–ncRNA dynamic network. Our results revealed that seedlings with active nodules exhibited enhanced drought tolerance by reserving energy, synthesizing N-glycans, and medicating systemic acquired resistance due to the early effects of symbiotic nitrogen fixation (SNF) triggered in contrast to the drought susceptible with inactive nodules. The improved drought tolerance might be involved in the decreased expression levels of miRNA such as mtr_miR169l-5p, mtr_miR398b, and mtr_miR398c and its target genes in seedlings with active nodules. Based on the negative expression pattern between miRNA and its target genes, we constructed an mRNA–miR169l–ncRNA ceRNA network. During severe drought stress, the lncRNA alternative splicings TCONS_00049507 and TCONS_00049510 competitively interacted with mtr_miR169l-5p, which upregulated the expression of NUCLEAR FACTOR-Y (NF-Y) transcription factor subfamily NF-YA genes MtNF-YA2 and MtNF-YA3 to regulate their downstream drought-response genes. Our results emphasized the importance of SNF plants affecting drought tolerance. In conclusion, our work provides insight into ceRNA involvement in rhizobium symbiosis contributing to drought tolerance and provides molecular evidence for future study.

: Torenia fournieri Lind. is an ornamental plant, popular for its numerous flowers and variety of colors. However, its genomic evolution, as well as the genetic and metabolic basis of flower color formation, remain poorly understood. Here we report a chromosome-level reference genome of T. fournieri comprising 164.4 Mb. Phylogenetic analysis revealed the phylogenetic placement of the species, and comparative genomics analysis indicated that T. fournieri shared a whole genome duplication (WGD) event with Antirrhinum majus . Through joint transcriptomics and metabolomics analyses, we characterized the differential genes and metabolites in the anthocyanin synthesis pathway in five T. fournieri varieties. We identified many metabolites related to pelargonidin, peonidin, and naringenin in Rose (R) color samples. On the other hand, the blue (B) and blue-violet (D) color samples contained many metabolites related to petunidin, cyanidin, quercetin, and malvidin. The formation of different flower colors in T. fournieri involves multiple genes and metabolites. We analyzed the results and obtained significantly different genes and metabolites related to the biosynthesis of flavonoids and anthocyanins, which are key metabolites in the formation of different flower colors. Our T. fournieri genome data provide a basis for studying the differentiation of this species and provide a valuable model genome enabling genetic studies and genomics-assisted breeding of T. fournieri . Highlight: The genome of Torenia fournieri was reported for the first time, and the formation mechanism of different colors in Torenia fournieri flowers was analyzed by genomics, transcriptomics and metabolomics.