Reference nodule transcriptomes for and cv. Algonquin.

Host/symbiont compatibility is a hallmark of the symbiotic nitrogen-fixing interaction between rhizobia and legumes, mediated in part by plant-produced nodule-specific cysteine-rich (NCR) peptides and the bacterial BacA membrane protein that can act as a NCR peptide transporter. In addition, the genetic and metabolic properties supporting symbiotic nitrogen fixation often differ between compatible partners, including those sharing a common partner, highlighting the need for multiple study systems. Here, we report high-quality nodule transcriptome assemblies for cv. Algonquin and , two legumes able to form compatible symbioses with . The compressed and assemblies consisted of 79,978 and 64,593 contigs, respectively, of which 33,341 and 28,278 were assigned putative annotations, respectively. As expected, the two transcriptomes showed broad similarity at a global level. We were particularly interested in the NCR peptide profiles of these plants, as these peptides drive bacterial differentiation during the symbiosis. A total of 412 and 308 NCR peptides were predicted from the and transcriptomes, respectively, with approximately 9% of the transcriptome of both species consisting of transcripts. Notably, transcripts encoding highly cationic NCR peptides (isoelectric point > 9.5), which are known to have antimicrobial properties, were ∼2-fold more abundant in than in , and ∼27-fold more abundant when considering only NCR peptides in the six-cysteine class. We hypothesize that the difference in abundance of highly cationic NCR peptides explains our previous observation that some rhizobial alleles which can support symbiosis with are unable to support symbiosis with .