Rodrigues Joana, Viegas Wanda, Silva Manuela
Linking Landscape, Environment, Agriculture and Food (LEAF), Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, Portugal.
PLoS One. 2017 Apr 27;12(4):e0176170. doi: 10.1371/journal.pone.0176170. eCollection 2017.
The genus Avena comprises four distinct genomes organized in diploid (AA or CC), tetraploid (AABB or AACC) and hexaploid species (AACCDD), constituting an interesting model for phylogenetic analysis. The aim of this work was to characterize 45S rDNA intergenic spacer (IGS) variability in distinct species representative of Avena genome diversity-A. strigosa (AA), A. ventricosa (CvCv), A. eriantha (CpCp), A. barbata (AABB), A. murphyi (AACC), A. sativa (AACCDD) and A. sterilis (AACCDD) through the assessment of the 5' external transcribed spacer (5'-ETS), a promising IGS region for phylogenetic studies poorly studied in Avena genus. In this work, IGS length polymorphisms were detected mainly due to distinct 5'-ETS sequence types resulting from major differences in the number and organization of repeated motifs. Although species with A genome revealed a 5'-ETS organization (A-organization) similar to the one previously described in A. sativa, a distinct organization was unraveled in C genome diploid species (C-organization). Interestingly, such new organization presents a higher similarity with other Poaceae species than A-genome sequences, supporting the hypothesis of C-genome being the ancestral Avena genome. Additionally, polyploid species with both genomes mainly retain the A-genome 5'-ETS organization, confirming the preferential elimination of C-genome sequences in Avena polyploid species. Moreover, 5'-ETS sequences phylogenetic analysis consistently clustered the species studied according to ploidy and genomic constitution supporting the use of ribosomal genes to highlight Avena species evolutive pathways.
燕麦属包含四个不同的基因组，以二倍体（AA或CC）、四倍体（AABB或AACC）和六倍体物种（AACCDD）的形式存在，构成了一个用于系统发育分析的有趣模型。这项工作的目的是通过评估5'外部转录间隔区（5'-ETS）来表征燕麦基因组多样性的不同代表物种——野燕麦（AA）、大燕麦（CvCv）、毛燕麦（CpCp）、芒颖燕麦（AABB）、墨菲燕麦（AACC）、普通燕麦（AACCDD）和不育燕麦（AACCDD）中45S rDNA基因间隔区（IGS）的变异性，5'-ETS是燕麦属中一个在系统发育研究中未得到充分研究但很有前景的IGS区域。在这项工作中，检测到IGS长度多态性主要是由于重复基序数量和组织的重大差异导致的不同5'-ETS序列类型。尽管具有A基因组的物种显示出与先前在普通燕麦中描述的5'-ETS组织（A组织）相似，但在C基因组二倍体物种中发现了一种不同的组织（C组织）。有趣的是，这种新组织与其他禾本科物种的相似度高于A基因组序列，支持了C基因组是燕麦属祖先基因组的假设。此外，具有两个基因组的多倍体物种主要保留A基因组的5'-ETS组织，证实了燕麦多倍体物种中C基因组序列的优先消除。此外，5'-ETS序列的系统发育分析根据倍性和基因组组成一致地将研究的物种聚类，支持使用核糖体基因来突出燕麦属物种的进化途径。
