MicroRNA160 is a class of nitrogen-starvation responsive genes which governs establishment of root system architecture by down-regulating AUXIN RESPONSE FACTOR genes (ARF10, ARF16 and ARF17) in plants. The high copy number of MIR160 variants discovered by us from land plants, especially polyploid crop Brassicas, posed questions regarding genesis, duplication, evolution and function. Absence of studies on impact of whole genome and segmental duplication on retention and evolution of MIR160 homologs in descendent plant lineages prompted us to undertake the current study. Herein, we describe ancestry and fate of MIR160 homologs in Brassicaceae in context of polyploidy driven genome re-organization, copy number and differentiation. Paralogy amongst Brassicaceae MIR160a, MIR160b and MIR160c was inferred using phylogenetic analysis of 468 MIR160 homologs from land plants. The evolutionarily distinct MIR160a was found to represent ancestral form and progenitor of MIR160b and MIR160c. Chronology of evolutionary events resulting in origin and diversification of genomic loci containing MIR160 homologs was delineated using derivatives of comparative synteny. A prescient model for causality of segmental duplications in establishment of paralogy in Brassicaceae MIR160, with whole genome duplication accentuating the copy number increase, is being posited in which post-segmental duplication events viz. differential gene fractionation, gene duplications and inversions are shown to drive divergence of chromosome segments. While mutations caused the diversification of MIR160a, MIR160b and MIR160c, duplicated segments containing these diversified genes suffered gene rearrangements via gene loss, duplications and inversions. Yet the topology of phylogenetic and phenetic trees were found congruent suggesting similar evolutionary trajectory. Over 80% of Brassicaceae genomes and subgenomes showed a preferential retention of single copy each of MIR160a, MIR160b and MIR160c suggesting functional relevance. Thus, our study provides a blue-print for reconstructing ancestry and phylogeny of MIRNA gene families at genomics level and analyzing the impact of polyploidy on organismal complexity. Such studies are critical for understanding the molecular basis of agronomic traits and deploying appropriate candidates for crop improvement.

MicroRNA160是一类氮饥饿响应基因，它通过下调植物中的AUXIN RESPONSE FACTOR基因（ARF10、ARF16和ARF17）来控制根系结构的建立。我们从陆地植物中发现的高拷贝数MIR160变体，特别是多倍体作物芸苔属植物，提出了关于起源、复制、进化和功能的问题。缺乏关于全基因组和片段重复对后代植物谱系中MIR160同源物的保留和进化的影响的研究促使我们进行当前的研究。在这里，我们描述MIR160的血统和命运多倍体驱动的基因组重组、拷贝数和分化背景下的十字花科同源物。使用来自陆地植物的 468 个MIR160同源物的系统发育分析推断出十字花科MIR160a、MIR160b和MIR160c之间的同源性。发现进化上不同的MIR160a代表MIR160b和MIR160c 的祖先形式和祖先。导致包含MIR160的基因组位点的起源和多样化的进化事件的年表使用比较同线性的衍生物来描绘同源物。在十字花科MIR160中建立旁系学的节段重复因果关系的先见之明模型，全基因组复制加剧了拷贝数的增加，正在假定其中后节段复制事件即。差异基因分离、基因重复和倒位被证明会导致染色体片段的分化。而突变导致MIR160a、MIR160b和MIR160c的多样化，包含这些多样化基因的重复片段通过基因丢失、重复和倒位遭受基因重排。然而，系统发育树和表型树的拓扑结构被发现一致，表明进化轨迹相似。超过 80% 的十字花科基因组和亚基因组显示优先保留MIR160a、MIR160b和MIR160c 中的每一个，表明功能相关性。因此，我们的研究为在基因组水平上重建MIRNA基因家族的祖先和系统发育提供了蓝图，并分析了多倍性对生物复杂性的影响。这些研究对于了解农艺性状的分子基础和部署合适的作物改良候选物至关重要。