Genome-Wide Analysis of the () Members in Alfalfa and the Involvement of in Nitrogen Assimilation.

The LATERAL ORGAN BOUNDARIES DOMAIN (LBD) proteins, a transcription factor family specific to the land plants, have been implicated in multiple biological processes including organ development, pathogen response and the uptake of inorganic nitrogen. The study focused on s in legume forage . The genome-wide analysis revealed that in 178 loci across 31 allelic chromosomes encoded 48 unique LBDs (MsLBDs), and the genome of its diploid progenitor spp. encoded 46 s. Synteny analysis indicated that the expansion of s was attributed to the whole genome duplication event. The MsLBDs were divided into two major phylogenetic classes, and the LOB domain of the Class I members was highly conserved relative to that of the Class II. The transcriptomic data demonstrated that 87.5% of s were expressed in at least one of the six test tissues, and Class II members were preferentially expressed in nodules. Moreover, the expression of Class II s in roots was upregulated by the treatment of inorganic nitrogen such as KNO and NHCl (0.3 mM). The overexpression of , a Class II member, in resulted in growth retardance with significantly declined biomass compared with the non-transgenic plants, and the transcription level of the genes involved in nitrogen uptake or assimilation, including , , and was repressed. Therefore, the LBDs in are highly conserved with their orthologs in embryophytes. Our observations that ectopic expression of inhibited growth by repressing nitrogen adaption suggest the negative role of the transcription factor in plant uptake of inorganic nitrogen. The findings imply the potential application of in yield improvement via gene editing.