Genome-Wide Analysis of Genes From an Early-Diverging Angiosperm .

genes are the largest gene family in plants conferring resistance to pathogens. At present, studies on the evolution of genes in angiosperms mainly focused on monocots and eudicots, while studies on genes in the basal angiosperms are limited. represents an early-diverging angiosperm order, Nymphaeales, and confronts various pathogens during its lifetime, which can cause serious economic losses in terms of yield and quality. In this study, we performed a genome-wide identification and analysis of genes in . All 131 identified genes could be divided into three subclasses according to different domain combinations, including 18 , 40 , and 73 . The genes are unevenly distributed on 29 chromosomes; 87 genes are clustered at 18 multigene loci, and 44 genes are singletons. Gene duplication analysis revealed that segmental duplications acted as a major mechanism for gene expansions but not for genes, because 18 genes were scattered over 11 chromosomes without synteny loci, indicating that the expansion of genes could have been caused by ectopic duplications. Ancestral gene reconciliation based on phylogenetic analysis revealed that there were at least 122 ancestral lineages in the common ancestor of the three Nymphaeaceae species, suggesting that genes expanded slightly during speciation in . Transcriptome analysis showed that the majority of genes were at a low level of expression without pathogen stimulation. Overall, this study characterized the profile of genes in and should serve as a valuable resource for disease resistance breeding in .