| Tree breeders have focused much attention on polyploid trees because of their importance to forestry. To evaluate the impact of intraspecies genome duplication on phenotype and transcriptome, morphology, photosynthesis, physiology, pollen characterist and transcriptome were measured between diploid and autotetraploid. These results shed light on variations in birch autotetraploidization and help identify important genes for the genetic engineering of birch trees. These results were as follows:There were significant variations in leaf morphology between diploid and autotetraploid. The leaf area and stoma length of autotetraploid were increased10.54%and95.73%respectively compared to those of diploid. The photosynthsis of autotetraploid was superior to that of diploid. The net photosynthetic rate, actual photochemical efficiency of PS Ⅱ and photochemical quenching of autotetraploid were increased13.33%,12.38%and10.68%respectively compared to those of diploid. There were significant variations in physiology and plant hormones between diploid and autotetraploid. The content of soluble sugar, soluble protein, chlorophyll, auxin, abscisic acid, gibberellin of autotetraploid were increased8.24%,12.52%,6.21%,32.93%,13.15%and34.93%respectively compared to those of diploid. The size of flower was larger in autotetraploid compared with diploid. The length of catkin and primary bract from staminate flowers, pollen diameter, the length and diameter of fruit of autotetraploid were increased44.02%,9.30%,27.75%.16.40%and33.69%respectively compared to those of diploid. The sterility of autotetraploid was reflected in male gamete. The germination rate of pollen in autotetraploid was decreased64.66%compared to that of diploid. In addition, there were significant variations in growth and reproduction in different autotetraploids.In the present study, we compared differences between transcriptomes of diploid and autotetraploid using Solexa sequencing technology. Short reads were assembled into unigenes, taking the distance of pair-end reads into account. All of the sequences were assembled, yielding132427non-redundant unigenes. Approximately47.61%of the unigenes were annotated by Blastx and Blastn against six public databases (Nr, Nt, Swiss-Prot, KEGG, COG and GO), with a threshold of10-5. The E-value distribution of the top hits in the Nr database revealed that55.78%of the mapped sequences showed strong homology (E-value≤10-30), and17.99%of the sequences shared greater than80%similarity. Nearly34.08%of the unigenes could be annotated using sequences from Vitis vinifera which was the most top-hit specie. Transcriptome data revealed numerous changes in gene expression attributable to autotetraploidization, which resulted in the upregulation of1166unigenes and the downregulation of890unigenes. GO enrichment analysis revealed that significant differences were seen between autotetraploid and diploid in the GO categories killing of cells of other organism, cellular response to molecule of bacterial origin, cell killing, iron ion binding, protein serine/threonine phosphatase activity, heme binding, monooxygenase activity, high affinity copper ion transmembrane transporter activity and tetrapyrrole binding. Differences in the dynamics and absolute levels of unigene expression between autotetraploid and diploid were seen in the following categories:RNA polymerase, pyrimidine metabolism, plant-pathogen interaction, purine metabolism, stilbenoid, diarylheptanoid and gingerol biosynthesis, limonene and pinene degradation and biosynthesis of secondary metabolites. Transcriptome analysis revealed that143genes involved in RNA polymerase, basal transcription factors, ribosome, plant hormone biosynthesis and signal transduction, sugar metabolism, circadian rhythm were altered after genome duplication, which may have contributed to phenotypic changes. |
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