Study On Mitochondrial Genome Of Ginkgo Biloba

Ginkgo biloba was an important economic plant,in order to better understand G.biloba at molecular level,the study taken the endosperm of G.biloba as material,sequenced the whole genome of G.biloba.After sequencing,we assembled and annotated the mitochondrial genome and explored the evolutionary status of G.biloba.At the same time,through comparing and analyzing the mitogenomes of 38 different types of plants(including G.biloba),we summarized the change rules of the mitogenome with the evolution of plants.The main results were as follows:1.The whole genome sequencing of G.biloba built ten libraries,each library inserted 400 bp fragment,the method of sequencing was PE250 Illumina high-throughput sequencing,and finally we acquired 430 Gb second generation datas.After comparison,we got 2×13Gb mitogenome datas of G.biloba,including 2×49325044 reads,which could be connected to 45 contigs.There were 4 gaps after assembling the contigs into primary sequence,and then we complemented the mitogenome of G.biloba by test.2.The mitogenome size of G.biloba was 346595 bp,and its base composition respectively was A(24.46%),T(25.18%),C(25.43%)and G(24.93%).The mitogenome of G.biloba had 67 genes,including 41 protein-coding genes,23 tRNA genes and 3 rRNA genes.There were 82 repetitive sequences in the mitogenome of G.biloba,which accounted for 8.6% of its total length.In addition,the mitogenome of G.biloba was also detected 240 SSRs and 1253 RNA editing sites.3.In order to explore the evolutionary status of G.biloba,the study structured tree analysis of ML,NJ and MP which was based on the 15 protein-coding genes? amino acid sequences of 25 species?(including G.biloba)mitogenomes.These 25 species involved two algaes,five bryophytes,one fern,three gymnosperms and fourteen angiosperms.G.biloba was most closely related to Cycas taitungensis in all three methods,and the next was Welwitschia mirabilis and angiosperms.The results of three kinds of tree analysis were generally consistent which were clustered according to different evolutionary types of algaes,bryophytes,ferns,gymnosperms and angiosperms.4.Through the comparative analysis of 38 different types of plants,we found that the mitogenome of G.biloba was medium size,which was slightly smaller than C.taitungensis,but larger than ordinary algaes and bryophytes.From lower plants to higher plants,the size of mitogenomes showed a tortuous rise.In terms of base content of genome,only G.biloba and W.mirabilis?s GC content was more than 50%.Most algaes? GC content was low,bryophytes? had no obvious rule,gymnosperms? GC content was high with an average of 50.1% and angiosperms? GC content was much more stable which was basically between 44% and 46%.In general,the GC content of plant mitogenomes tended to be steady along with evolution.In the case of mitochondrial genetic makeup,protein-coding genes and tRNA genes were generally decreasing with evolution of species,but the type and the amount of rRNA genes were conservative.As for repetitive sequence,the proportion of repetitive sequences in the mitogenome of 38 plants showed a general increase.The mitogenome of G.biloba contained 0.72% chloroplast migratory section,and other plants also existed similar genetic migrations.