Park Sang-Hyuck, Kyndt John A, Brown Judith K
School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
Institute of Cannabis Research, Colorado State University-Pueblo, Pueblo, CO 81001, USA.
Life (Basel). 2022 Mar 20;12(3):458. doi: 10.3390/life12030458.
Resequencing of the chloroplast genome (cpDNA) of UTEX 25 was completed (GenBank Accession no. KC631634.1), revealing a genome size of 84,576 base pairs and 30.8% GC content, consistent with features reported for the previously sequenced 0710, (GenBank Accession no. KC843975). The UTEX 25 cpDNA encoded 78 predicted open reading frames, 32 tRNAs, and 4 rRNAs, making it smaller and more compact than the cpDNA genome of (124,579 bp) and (150,613 bp). By comparison, the compact genome size of was attributable primarily to a lower intergenic sequence content. The cpDNA coding regions of all known species were found to be organized in conserved colinear blocks, with some rearrangements. The and species genome structure and composition were similar, and of particular interest were genes influencing photosynthetic efficiency, i.e., chlorophyll synthesis and photosystem subunit I and II genes, consistent with other biofuel species of interest. Phylogenetic analysis revealed that is the closest known relative, followed by members of the genus . The cpDNA of encodes 37 genes that are highly homologous to representative cyanobacteria species, including , , and , corroborating a well-recognized symbiosis. Several putative coding regions were identified that shared high nucleotide sequence identity with virus-like sequences, suggestive of horizontal gene transfer. Despite these predictions, no corresponding transcripts were obtained by RT-PCR amplification, indicating they are unlikely to be expressed in the extant lineage.
完成了对UTEX 25叶绿体基因组（cpDNA）的重测序（GenBank登录号：KC631634.1），结果显示其基因组大小为84,576个碱基对，GC含量为30.8%，这与之前测序的0710（GenBank登录号：KC843975）所报道的特征一致。UTEX 25的cpDNA编码了78个预测的开放阅读框、32个tRNA和4个rRNA，使其比（124,579 bp）和（150,613 bp）的cpDNA基因组更小且更紧凑。相比之下，基因组紧凑的原因主要是基因间序列含量较低。所有已知物种的cpDNA编码区域都以保守的共线性模块形式组织，不过存在一些重排。物种的基因组结构和组成相似，特别值得关注的是影响光合效率的基因，即叶绿素合成基因以及光系统亚基I和II基因，这与其他有研究价值的生物燃料物种一致。系统发育分析表明，是已知最接近的亲属，其次是属的成员。UTEX 25的cpDNA编码了37个与代表性蓝藻物种高度同源的基因，包括、和，这证实了一种广为人知的共生关系。还鉴定出了几个与病毒样序列具有高核苷酸序列同一性的推定编码区域，这表明存在水平基因转移。尽管有这些预测，但通过RT-PCR扩增未获得相应的转录本，这表明它们不太可能在现存谱系中表达。
