MicroRNAs are important regulators of gene expression in eukaryotes. Previously, we reported that in Phaseolus vulgaris, the precursor for miR2119 is located in the same gene as miR398a, conceiving a dicistronic MIR gene. Both miRNA precursors are transcribed and processed from a single transcript resulting in two mature microRNAs that regulate the mRNAs encoding ALCOHOL DEHYDROGENASE 1 (ADH1) and COPPER-ZINC SUPEROXIDE DISMUTASE 1 (CSD1). Genes for miR398 are distributed throughout the spermatophytes; however, miR2119 is only found in Leguminosae species, indicating its recent emergence. Here, we used public databases to explore the presence of the miR2119 sequence in several plant species. We found that miR2119 is present only in specific clades within the Papilionoideae subfamily, including important crops used for human consumption and forage. Within this subfamily, MIR2119 and MIR398a are found together as a single gene in the genomes of the Millettioids and Hologalegina. In contrast, in the Dalbergioids MIR2119 is located in a different locus from MIR398a, suggesting this as the ancestral genomic organization. To our knowledge, this is a unique example where two separate MIRNA genes have merged to generate a single polycistronic gene. Phylogenetic analysis of ADH1 gene sequences in the Papilionoideae subfamily revealed duplication events resulting in up to four ADH1 genes in certain species. Notably, the presence of MIR2119 correlates with the conservation of target sites in particular ADH1 genes in each clade. Our results suggest that post-transcriptional regulation of ADH1 genes by miR2119 has contributed to shaping the expansion and divergence of this gene family in the Papilionoideae. Future experimental work on ADH1 regulation by miR2119 in more legume species will help to further understand the evolutionary history of the ADH1 gene family and the relevance of miRNA regulation in this process.

中文翻译：

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豆类中 miR2119 和 ADH1 调节模块的起源和进化动力学

MicroRNA 是真核生物基因表达的重要调节因子。此前，我们报道了在菜豆中，miR2119 的前体与 miR398a 位于同一基因中，构想出一个双顺反子MIR基因。两种 miRNA 前体都从单个转录本转录和加工，产生两个成熟的 microRNA，可调节编码酒精脱氢酶 1 (ADH1) 和铜锌超氧化物歧化酶 1 (CSD1) 的 mRNA。miR398 的基因分布在整个精子植物中；然而，miR2119 仅在豆科物种中发现，表明它是最近出现的。在这里，我们使用公共数据库来探索 miR2119 序列在几种植物物种中的存在。我们发现 miR2119 仅存在于蝶形亚科的特定进化枝中，包括用于人类消费和饲料的重要作物。在这个亚科中，MIR 2119 和MIR398a 在 Millettioids 和 Hologalegina 的基因组中作为单个基因一起被发现。相比之下，在黄檀中，MIR 2119 位于与MIR 398a不同的位点，表明这是祖先的基因组组织。据我们所知，这是一个独特的例子，其中两个单独的MIRNA基因合并生成一个多顺反子基因。蝶形亚科中ADH1基因序列的系统发育分析揭示了重复事件导致某些物种中多达四个ADH1基因。值得注意的是，MIR 2119 的存在与目标位点的保守性相关，特别是ADH1每个进化枝中的基因。我们的结果表明，miR2119对ADH1基因的转录后调控有助于塑造凤蝶科中该基因家族的扩展和分化。未来在更多豆科植物中通过miR2119调控 ADH1 的实验工作将有助于进一步了解ADH1基因家族的进化历史以及 miRNA 调控在该过程中的相关性。