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资助项目
GST,p < 0.001) and low levels of seed-based gene flow. C. debaoensis (Cycadaceae) is an endangered species restricted to the border of Guangxi and Yunnan province in southwest China. This species has been classified into two types: sand and karst, according to the soil matrix they grow on. We examined chloroplast sequence variation of the cpDNA sequences from 11 populations of this species. Significant population genetic differentiation was detected (GST= 0.684 and FST = 0.74160). There was marked genetic differentiation between populations in the sand and karst regions and no expansion was detected. Climate changes during glacial periods have had significant effects on the current distribution of cycads. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest that C. debaoensis experienced range contraction during glacial periods, and that the current populations are still confined to the original refugia in southwest China which have favorable habitats in glacial period. These results imply that small refugia were maintained in both sand and karst regions during the LGM (last glacial maximum). This species had no postglacial recolonization and only stayed in these refugia up to now. The low within-population diversity of C. debaoensis suggests that there were strong bottleneck events or founder effects within each separate region during the Quaternary climatic oscillations. Relatively high genetic and haplotype diversities were detected in the newly discovered populations, which located at intermediate locality of sand regions and had morphological variation; this is probably the consequence of the admixture of different haplotypes colonizing the area from separate sources. C. micholitzii occurs in the Annan Highlands in central Vietnam near the Laos border. C. bifida occurs in North Vietnam; its distribution extends across the border into adjacent localities in Guangxi and Yunnan in China. For the comparability between them,theywere considered as the same species C. micholitzii by many academicians. The cpDNA sequences from 11 populations showed that these very controversial species, C. micholitzii and C. bifida, is paraphyletic and should belong to the same species C. micholitzii. AMOVA analysis showed that the component of among-population within region/species (76.46%) was unexpectedly larger than the among-species/region component (14.97%), which also indicates that there is no justification for recognizing two species as C. micholitzii and C. bifida. This hypothesis was also supported by the geological data, especially the neotectonic history of the indo-china block, which started to move south since Oligocene and cause the geographic isolation of these two groups. Therefore, the most likely explanation to the phenotypic similarities between these two groups may be the retention of ancestral polymorphisms in the paraphyletic group due to incomplete lineage sorting. Furthermore, the similarities may also be ascribed to pollen-mediated gene flow among geographically proximate populations and/or phenotypic convergence under similar selection schemes in the same region. C.micholitzi had the higest genetic diversity (HT = 0.980,) and genetic differentiation (GST = 0.830, NST = 0.915) among the C. micholitzii complex. The high genetic diversity might be attributed to its long evolutionary history, highly diverse habitats. The ineffective mode of seed dispersal and dramatic neotectonic movement in the distribution range of this species could result in the high genetic differentiation. 2. Phylogeographic analysis based on nuclear ribosomal sequences, We sequenced the nrDNA ITS in all 27 populations sampled, 7 haplotypes were identified, among which C. micholitzii had 6, while C. multipinnata, C. longipetiolula and C. debaoensis shared the remaining one. Compared to chloroplast genes, nuclear genes had higher correlation between genetic and geographical distance, but lower interspecies differentiation (54.42% vs 25.24%). Phylogeographical structure of C. micholitzii and C.bifida based on ITS Variation was consistent with the morphology differentiation. This similar in nuclear gene should be ascribed to pollen-mediated gene flow among geographically proximate populations.Long-distance gene flow over the two groups was clearly interrupted, which brought on the nrDNA genetic differenciation between the geographically isolated groups, to a certain extent affected the morphological variation. 3. Interspecies relationships among Cycas micholitzii complex, We analysed chloroplast sequence variation of the atpB-rbcL and psbA-trnH intergenic spacers in 27 populations sampled of C. micholitzii complex, AMOVA analysis showed that the component of among-species/region component (59.21%). However, phylogenic analysis showed that the haplotypes of C. micholitzii complex couldn`t grouped into four clusters closely corresponding to the narrowly defined C. micholitzi, C. multipinnata, C. debaoensis and C. longipetiolula. We concluded that the conflict may result from several factors: firstly incomplete lineage sorting of C. micholitzii; secondly hybridization/introgression of sympatrically cycads, which would be supported by evidence base on nrDNA ITS sequences; thirdly intramolecular recombination in cpDNA of cycads; eventually the neotectonic movement in the distribution range of this species.","jscount":"1","jsurl":"/simple-search?field1=all&field=dc.type_filter&advanced=false&query1=PRIMER%2BSETS&&fq=dc.project.title_filter%3ACycas%5C+micholitzii%5C+complex%5C+is%5C+composed%5C+of%5C+5%5C+species%5C%3A%5C+C.%5C+micholitzii%5C+Dyer%2C%5C+C.%5C+bifida%5C+%5C%28Dyer%5C%29%5C+K.%5C+D.%5C+Hill%2CC.%5C+longipetiolula%5C+D.%5C+Y.%5C+Wang%2C%5C+C.%5C+debaoensis%5C+Y.%5C+C.%5C+Zhong%5C+et%5C+C%5C+J.%5C+Chen%2C%5C+C.%5C+multipinnata%5C+C%5C+J.%5C+Chen%5C+et%5C+S.%5C+Y.%5C+Yang%EF%BC%8Cand%5C+distributed%5C+from%5C+southwest%5C+China%5C+to%5C+central%5C+Vietnam%5C+and%5C+eastern%5C+Laos.%5C+Based%5C+on%5C+sequence%5C+data%5C+from%5C+two%5C+maternally%5C+inherited%5C+cpDNA%5C+and%5C+one%5C+biparentally%5C+nuclear%5C+DNA%5C+fragments%2C%5C+our%5C+study%5C+revealed%5C+the%5C+population%5C+genetic%5C+structure%5C+of%5C+C.%5C+micholitzii%5C+complex%5C+and%5C+explored%5C+the%5C+potential%5C+causes.%5C+The%5C+evolutionary%5C+and%5C+demographic%5C+histories%5C+were%5C+investigated.%5C+The%5C+genetic%5C+relationship%5C+among%5C+species%5C+in%5C+the%5C+complex%5C+was%5C+also%5C+clarified.The%5C+results%5C+were%5C+summarized%5C+as%5C+follows%5C%3A%5C+1.%5C+Phylogeographic%5C+analysis%5C+based%5C+on%5C+chloroplast%5C+sequences%EF%BC%8CWe%5C+examined%5C+chloroplast%5C+sequence%5C+variation%5C+of%5C+the%5C+atpB%5C-rbcLand%5C+psbA%5C-trnHintergenic%5C+spacers%5C+in%5C+27%5C+populations%5C+of%5C+C.%5C+micholitzii%5C+complex%2C%5C+recovering%5C+26%5C+haplotypes.%5C+The%5C+average%5C+within%5C-population%5C+diversity%5C+%5C%28HS%5C+%3D%5C+0.140%5C%29%5C+was%5C+low%5C+while%5C+total%5C+diversity%5C+%5C%28HT%5C+%3D%5C+0.911%5C%29%5C+was%5C+high.%5C+Population%5C+differentiation%5C+was%5C+also%5C+high%5C%28GST%5C+%3D%5C+0.846%2C%5C+NST%5C+%3D%5C+0.919%5C%29%2C%5C+indicating%5C+significant%5C+phylogeographical%5C+structure%5C+%5C%28NST%5C+%3E%5C+GST%2Cp%5C+%3C%5C+0.001%5C%29%5C+and%5C+low%5C+levels%5C+of%5C+seed%5C-based%5C+gene%5C+flow.%5C+C.%5C+debaoensis%5C+%5C%28Cycadaceae%5C%29%5C+is%5C+an%5C+endangered%5C+species%5C+restricted%5C+to%5C+the%5C+border%5C+of%5C+Guangxi%5C+and%5C+Yunnan%5C+province%5C+in%5C+southwest%5C+China.%5C+This%5C+species%5C+has%5C+been%5C+classified%5C+into%5C+two%5C+types%5C%3A%5C+sand%5C+and%5C+karst%2C%5C+according%5C+to%5C+the%5C+soil%5C+matrix%5C+they%5C+grow%5C+on.%5C+We%5C+examined%5C+chloroplast%5C+sequence%5C+variation%5C+of%5C+the%5C+cpDNA%5C+sequences%5C+from%5C+11%5C+populations%5C+of%5C+this%5C+species.%5C+Significant%5C+population%5C+genetic%5C+differentiation%5C+was%5C+detected%5C+%5C%28GST%3D%5C+0.684%5C+and%5C+FST%5C+%3D%5C+0.74160%5C%29.%5C+There%5C+was%5C+marked%5C+genetic%5C+differentiation%5C+between%5C+populations%5C+in%5C+the%5C+sand%5C+and%5C+karst%5C+regions%5C+and%5C+no%5C+expansion%5C+was%5C+detected.%5C+Climate%5C+changes%5C+during%5C+glacial%5C+periods%5C+have%5C+had%5C+significant%5C+effects%5C+on%5C+the%5C+current%5C+distribution%5C+of%5C+cycads.%5C+The%5C+molecular%5C+phylogenetic%5C+data%2C%5C+together%5C+with%5C+the%5C+geographic%5C+distribution%5C+of%5C+the%5C+haplotypes%2C%5C+suggest%5C+that%5C+C.%5C+debaoensis%5C+experienced%5C+range%5C+contraction%5C+during%5C+glacial%5C+periods%2C%5C+and%5C+that%5C+the%5C+current%5C+populations%5C+are%5C+still%5C+confined%5C+to%5C+the%5C+original%5C+refugia%5C+in%5C+southwest%5C+China%5C+which%5C+have%5C+favorable%5C+habitats%5C+in%5C+glacial%5C+period.%5C+These%5C+results%5C+imply%5C+that%5C+small%5C+refugia%5C+were%5C+maintained%5C+in%5C+both%5C+sand%5C+and%5C+karst%5C+regions%5C+during%5C+the%5C+LGM%5C+%5C%28last%5C+glacial%5C+maximum%5C%29.%5C+This%5C+species%5C+had%5C+no%5C+postglacial%5C+recolonization%5C+and%5C+only%5C+stayed%5C+in%5C+these%5C+refugia%5C+up%5C+to%5C+now.%5C+The%5C+low%5C+within%5C-population%5C+diversity%5C+of%5C+C.%5C+debaoensis%5C+suggests%5C+that%5C+there%5C+were%5C+strong%5C+bottleneck%5C+events%5C+or%5C+founder%5C+effects%5C+within%5C+each%5C+separate%5C+region%5C+during%5C+the%5C+Quaternary%5C+climatic%5C+oscillations.%5C+Relatively%5C+high%5C+genetic%5C+and%5C+haplotype%5C+diversities%5C+were%5C+detected%5C+in%5C+the%5C+newly%5C+discovered%5C+populations%2C%5C+which%5C+located%5C+at%5C+intermediate%5C+locality%5C+of%5C+sand%5C+regions%5C+and%5C+had%5C+morphological%5C+variation%5C%3B%5C+this%5C+is%5C+probably%5C+the%5C+consequence%5C+of%5C+the%5C+admixture%5C+of%5C+different%5C+haplotypes%5C+colonizing%5C+the%5C+area%5C+from%5C+separate%5C+sources.%5C+%5C+C.%5C+micholitzii%5C+occurs%5C+in%5C+the%5C+Annan%5C+Highlands%5C+in%5C+central%5C+Vietnam%5C+near%5C+the%5C+Laos%5C+border.%5C+C.%5C+bifida%5C+occurs%5C+in%5C+North%5C+Vietnam%5C%3B%5C+its%5C+distribution%5C+extends%5C+across%5C+the%5C+border%5C+into%5C+adjacent%5C+localities%5C+in%5C+Guangxi%5C+and%5C+Yunnan%5C+in%5C+China.%5C+For%5C+the%5C+comparability%5C+between%5C+them%2Ctheywere%5C+considered%5C+as%5C+the%5C+same%5C+species%5C+C.%5C+micholitzii%5C+by%5C+many%5C+academicians.%5C+The%5C+cpDNA%5C+sequences%5C+from%5C+11%5C+populations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of the Royal Botanic Gardens Victoria","jscount":"1","jsurl":"/simple-search?field1=all&field=dc.type_filter&advanced=false&query1=PRIMER%2BSETS&&fq=dc.project.title_filter%3AFriends%5C+of%5C+the%5C+Royal%5C+Botanic%5C+Gardens%5C+Victoria"},{"jsname":"Glory Light International Fellowship for Chinese Botanists at Missouri Botanical Garden","jscount":"1","jsurl":"/simple-search?field1=all&field=dc.type_filter&advanced=false&query1=PRIMER%2BSETS&&fq=dc.project.title_filter%3AGlory%5C+Light%5C+International%5C+Fellowship%5C+for%5C+Chinese%5C+Botanists%5C+at%5C+Missouri%5C+Botanical%5C+Garden"},{"jsname":"How has natural selection determined the evolution of gene regulation by acting on major regulatory factors? This question has been attractive to many evolutionary biologists for a long time. MicroRNAs (miRNAs) are endogenous posttranscriptional repressors and play essential roles in diverse biological processes in plants. To understand how natural selection has targeted on the entire lay of miRNA regulatory modules during flower development, we resequenced 31 miRNA target sites involved in flower development from five rice populations. We found that purifying selection serves as a major evolutionary force to act on the conserved miRNA binding sites, leading to the globally reduced genetic variation in highly conserved miRNA binding sequences within the entire rice samples. Conversely, positive selection allows variations at nonconserved miRNA binding sites and acts on them in a population-specific behaviour. Further analysis revealed that the polymorphisms within target sites may serve as raw materials for diverse functions of miRNAs by means of the destabilization of duplex, abolishment of existing target sites, and creation of novel ones. Together, the above-mentioned results indicate that variations at conserved binding sites are likely deleterious during rice flower development, whereas variants at nonconserved binding sites may be conductive to flower development-related phenotypic diversities and rice population adaption to variable environmental conditions as well. To further assess functional effects and evolutionary significance of variable alleles at the target genes, we reported the detailed characterization of the haplotype and linkage disequilibrium (LD) patterns of the entire target gene (LOC_Os01g18850，SPL 1) and the 1.4 Mb flanking regions in three rice populations, namely japonica, indica and O. rufipogon. The genetic profile of SNPs at target site and its flanking regions revealed high haplotype frequency, low haplotype diversity and strong LD in two cultivatedricepopulations. By contrast, we observed the opposite phenomena in O. rufipogon. Using the long-range haplotype (LRT) test, we found strong evidence of recent positive selection for SNP 3C/T alleles at target site in the combined O. sativa. Comparsion between the two rice subpopulations indicated that the major haplotype mh 2 containing SNP 3C accounts for half of all haplotypes in indica, while mh 3 containing SNP 3T is 91% in japonica. Moreover, the extent of LD is stronger in japonica than that in inidca. These differences suggest that independent evolutionary events may have occurred in target sequences of two cultivated rice populations and stronger positive selection acted on japonica. Next, we examined geographic distribution of polymorphic variants at target sites. We found that the major alleles SNP 3T and tightly linked SNP 4A in japonica appear to be associated with the adaption to the northern climates during rice flower development.","jscount":"1","jsurl":"/simple-search?field1=all&field=dc.type_filter&advanced=false&query1=PRIMER%2BSETS&&fq=dc.project.title_filter%3AHow%5C+has%5C+natural%5C+selection%5C+determined%5C+the%5C+evolution%5C+of%5C+gene%5C+regulation%5C+by%5C+acting%5C+on%5C+major%5C+regulatory%5C+factors%5C%3F%5C+This%5C+question%5C+has%5C+been%5C+attractive%5C+to%5C+many%5C+evolutionary%5C+biologists%5C+for%5C+a%5C+long%5C+time.%5C+MicroRNAs%5C+%5C%28miRNAs%5C%29%5C+are%5C+endogenous%5C+posttranscriptional%5C+repressors%5C+and%5C+play%5C+essential%5C+roles%5C+in%5C+diverse%5C+biological%5C+processes%5C+in%5C+plants.%5C+To%5C+understand%5C+how%5C+natural%5C+selection%5C+has%5C+targeted%5C+on%5C+the%5C+entire%5C+lay%5C+of%5C+miRNA%5C+regulatory%5C+modules%5C+during%5C+flower%5C+development%2C%5C+we%5C+resequenced%5C+31%5C+miRNA%5C+target%5C+sites%5C+involved%5C+in%5C+flower%5C+development%5C+from%5C+five%5C+rice%5C+populations.%5C+We%5C+found%5C+that%5C+purifying%5C+selection%5C+serves%5C+as%5C+a%5C+major%5C+evolutionary%5C+force%5C+to%5C+act%5C+on%5C+the%5C+conserved%5C+miRNA%5C+binding%5C+sites%2C%5C+leading%5C+to%5C+the%5C+globally%5C+reduced%5C+genetic%5C+variation%5C+in%5C+highly%5C+conserved%5C+miRNA%5C+binding%5C+sequences%5C+within%5C+the%5C+entire%5C+rice%5C+samples.%5C+Conversely%2C%5C+positive%5C+selection%5C+allows%5C+variations%5C+at%5C+nonconserved%5C+miRNA%5C+binding%5C+sites%5C+and%5C+acts%5C+on%5C+them%5C+in%5C+a%5C+population%5C-specific%5C+behaviour.%5C+Further%5C+analysis%5C+revealed%5C+that%5C+the%5C+polymorphisms%5C+within%5C+target%5C+sites%5C+may%5C+serve%5C+as%5C+raw%5C+materials%5C+for%5C+diverse%5C+functions%5C+of%5C+miRNAs%5C+by%5C+means%5C+of%5C+the%5C+destabilization%5C+of%5C+duplex%2C%5C+abolishment%5C+of%5C+existing%5C+target%5C+sites%2C%5C+and%5C+creation%5C+of%5C+novel%5C+ones.%5C+Together%2C%5C+the%5C+above%5C-mentioned%5C+results%5C+indicate%5C+that%5C+variations%5C+at%5C+conserved%5C+binding%5C+sites%5C+are%5C+likely%5C+deleterious%5C+during%5C+rice%5C+flower%5C+development%2C%5C+whereas%5C+variants%5C+at%5C+nonconserved%5C+binding%5C+sites%5C+may%5C+be%5C+conductive%5C+to%5C+flower%5C+development%5C-related%5C+phenotypic%5C+diversities%5C+and%5C+rice%5C+population%5C+adaption%5C+to%5C+variable%5C+environmental%5C+conditions%5C+as%5C+well.%5C+To%5C+further%5C+assess%5C+functional%5C+effects%5C+and%5C+evolutionary%5C+significance%5C+of%5C+variable%5C+alleles%5C+at%5C+the%5C+target%5C+genes%2C%5C+we%5C+reported%5C+the%5C+detailed%5C+characterization%5C+of%5C+the%5C+haplotype%5C+and%5C+linkage%5C+disequilibrium%5C+%5C%28LD%5C%29%5C+patterns%5C+of%5C+the%5C+entire%5C+target%5C+gene%5C+%5C%28LOC_Os01g18850%EF%BC%8CSPL%5C+1%5C%29%5C+and%5C+the%5C+1.4%5C+Mb%5C+flanking%5C+regions%5C+in%5C+three%5C+rice%5C+populations%2C%5C+namely%5C+japonica%2C%5C+indica%5C+and%5C+O.%5C+rufipogon.%5C+The%5C+genetic%5C+profile%5C+of%5C+SNPs%5C+at%5C+target%5C+site%5C+and%5C+its%5C+flanking%5C+regions%5C+revealed%5C+high%5C+haplotype%5C+frequency%2C%5C+low%5C+haplotype%5C+diversity%5C+and%5C+strong%5C+LD%5C+in%5C+two%5C+cultivatedricepopulations.%5C+By%5C+contrast%2C%5C+we%5C+observed%5C+the%5C+opposite%5C+phenomena%5C+in%5C+O.%5C+rufipogon.%5C+Using%5C+the%5C+long%5C-range%5C+haplotype%5C+%5C%28LRT%5C%29%5C+test%2C%5C+we%5C+found%5C+strong%5C+evidence%5C+of%5C+recent%5C+positive%5C+selection%5C+for%5C+SNP%5C+3C%5C%2FT%5C+alleles%5C+at%5C+target%5C+site%5C+in%5C+the%5C+combined%5C+O.%5C+sativa.%5C+Comparsion%5C+between%5C+the%5C+two%5C+rice%5C+subpopulations%5C+indicated%5C+that%5C+the%5C+major%5C+haplotype%5C+mh%5C+2%5C+containing%5C+SNP%5C+3C%5C+accounts%5C+for%5C+half%5C+of%5C+all%5C+haplotypes%5C+in%5C+indica%2C%5C+while%5C+mh%5C+3%5C+containing%5C+SNP%5C+3T%5C+is%5C+91%25%5C+in%5C+japonica.%5C+Moreover%2C%5C+the%5C+extent%5C+of%5C+LD%5C+is%5C+stronger%5C+in%5C+japonica%5C+than%5C+that%5C+in%5C+inidca.%5C+These%5C+differences%5C+suggest%5C+that%5C+independent%5C+evolutionary%5C+events%5C+may%5C+have%5C+occurred%5C+in%5C+target%5C+sequences%5C+of%5C+two%5C+cultivated%5C+rice%5C+populations%5C+and%5C+stronger%5C+positive%5C+selection%5C+acted%5C+on%5C+japonica.%5C+Next%2C%5C+we%5C+examined%5C+geographic%5C+distribution%5C+of%5C+polymorphic%5C+variants%5C+at%5C+target%5C+sites.%5C+We%5C+found%5C+that%5C+the%5C+major%5C+alleles%5C+SNP%5C+3T%5C+and%5C+tightly%5C+linked%5C+SNP%5C+4A%5C+in%5C+japonica%5C+appear%5C+to%5C+be%5C+associated%5C+with%5C+the%5C+adaption%5C+to%5C+the%5C+northern%5C+climates%5C+during%5C+rice%5C+flower%5C+development."},{"jsname":"lastIndexed","jscount":"2024-04-15"}],"资助项目","dc.project.title_filter")'>
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