Stepanenko Anton, Chen Guimin, Hoang Phuong T N, Fuchs Jörg, Schubert Ingo, Borisjuk Nikolai
Jiangsu Key Laboratory for Eco-Agricultural Biotechnology Around Hongze Lake and Jiangsu Collaborative Innovation Centre of Regional Modern Agriculture and Environmental Protection, School of Life Sciences, Huaiyin Normal University, Huai'an, China.
Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany.
Front Plant Sci. 2022 Mar 3;13:819750. doi: 10.3389/fpls.2022.819750. eCollection 2022.
The freshwater plant water lettuce ( L.) grows in warm climatic zones and is used for phytoremediation and biomass production. belongs to the Araceae, an ecologically and structurally diverse early monocot family, but the phylogenetic relationships among Araceae members are poorly understood. Ribosomal DNAs (rDNAs), including the 35S and 5S rDNA, encode the RNA components of ribosomes and are widely used in phylogenetic and evolutionary studies of various plant taxa. Here, we comprehensively characterized the chromosomal locations and molecular organization of 35S and 5S rDNA genes in water lettuce using karyological and molecular methods. Fluorescence hybridization revealed a single location for the 35S and 5S rDNA loci, each on a different pair of the species' 28 chromosomes. Molecular cloning and nucleotide sequencing of 35S rDNA of , the first representative Araceae in which such a study was performed, displayed typical structural characteristics. The full-length repeat showed high sequence conservation of the regions producing the 18S, 5.8S, and 25S rRNAs and divergence of the internal transcribed spacers ITS1 and ITS2 as well as the large intergenic spacer (IGS). Alignments of the deduced sequence of 18S rDNA with the sequences available for other Araceae and representatives of other clades were used for phylogenetic analysis. Examination of 11 IGS sequences revealed significant intra-genomic length variability due to variation in subrepeat number, with four types of units detected within the 35S rDNA locus of the genome (estimated size 407 Mb/1C). Similarly, the 5S rDNA locus harbors gene units comprising a conserved 119-bp sequence encoding 5S rRNA and two types of non-transcribed spacer (NTS) sequences. Type I was classified into four subtypes, which apparently originated via progressive loss of subrepeats within the duplicated NTS region containing the 3' part of the 5S rRNA gene. The minor Type II NTS is shorter than Type I and differs in nucleotide composition. Some DNA clones containing two or three consecutive 5S rDNA repeats harbored 5S rDNA genes with different types of NTSs, confirming the mosaic composition of the 5S rDNA locus.
淡水植物大薸（Pistia stratiotes L.）生长在温暖气候带，可用于植物修复和生物质生产。大薸属于天南星科，这是一个生态和结构多样的早期单子叶植物科，但天南星科成员之间的系统发育关系尚不清楚。核糖体DNA（rDNA），包括35S和5S rDNA，编码核糖体的RNA成分，广泛用于各种植物类群的系统发育和进化研究。在这里，我们使用核型分析和分子方法全面表征了大薸中35S和5S rDNA基因的染色体位置和分子组织。荧光原位杂交显示35S和5S rDNA位点各有一个单一位置，分别位于该物种28条染色体的不同对染色体上。对大薸35S rDNA进行分子克隆和核苷酸测序，这是首次对天南星科代表性植物进行此类研究，显示出典型的结构特征。全长重复序列在产生18S、5.8S和25S rRNA的区域显示出高度的序列保守性，而内部转录间隔区ITS1和ITS2以及大的基因间隔区（IGS）则存在差异。将推导的18S rDNA序列与其他天南星科植物和其他分支的代表序列进行比对，用于系统发育分析。对11个IGS序列的检查发现，由于亚重复序列数量的变化，基因组内存在显著的长度变异性，在大薸基因组（估计大小为407 Mb/1C）的35S rDNA位点内检测到四种类型的单元。同样，5S rDNA位点包含基因单元，由一个保守的119 bp序列编码5S rRNA和两种类型的非转录间隔区（NTS）序列组成。I型分为四个亚型，显然是通过在包含5S rRNA基因3'部分的重复NTS区域内亚重复序列的逐渐丢失而产生的。较小的II型NTS比I型短，核苷酸组成不同。一些包含两个或三个连续5S rDNA重复序列的DNA克隆含有具有不同类型NTS的5S rDNA基因，证实了5S rDNA位点的镶嵌组成。
