| Nuclear DNA amount involves DNA C-value and genome size.DNA C-value is an important biological concept,it has biological and ecology significance.There is a controversial about the reliability of the results about the nuclear DNA amount determination,it is unclear whether the different methods of determination results regularity of differences.The variation pattern of plant nuclear DNA content in different life forms on a global scale is not clear.Previous studies have focused on the relationship between latitude,altitude,average annual temperature and annual rainfall,but the relationship between nuclear DNA content and these environmental variables has been controversial,and the relationship between extreme weather conditions and other biological climate factors is not clear.It has been known that environmental nitrogen may be one of the driving factors of plant genome evolution,but the evidence only comes from individual groups of local environment,whether it is universal or not is not clear.To solve the above problems,we used FACSCalibur flow cytometry to determine the DNA 2C value data of 167 Echinochloa samples collected from the farmland environment in China.Linear model and gaussian model were used to analyze the geographic gradient law of the DNA 2C value of Echinochloa and the DNA 2C value of different types of Echinochloa on the latitude and longitude gradient.We used SPSS one-way anova to analyze the difference between flow cytometry and foul-root staining for the determination of nuclear DNA content.We compared the contents of nuclear DNA between invasive plants and native species,endangered species and nonendangered species with different ploidy.Based on the nuclear DNA content data and geographic distribution information of angiosperms such as poaceae,leguminosae and compositae,which have been measured worldwide,we used quantile regression analysis to analyze the relationship between the nuclear DNA content of these groups and environmental factors such as climate and nitrogen content.The above work aims at a more comprehensive understanding of the distribution of nuclear DNA content in plants and elucidating its possible biological,ecological and evolutionary significance.The main results are as follows:1.Among the 5,763 angiosperms whose nuclear DNA has been determined,we found that the genome size of the invasive species(150 species)was 1.631±0.166 pg,and that of the non-invasive species(5613 species)was 4.895±0.108 pg.The genome size of the invasive species was significantly smaller than that of the non-invasive species(p<0.001);For the Asteraceae plants,the genome size of the invasive species(24 species)was 1.583±0.146 pg,and that of the non-invasive species(706 species)was 2.925±0.076 pg.Similarly,the genome size of the invasive plants in this family was significantly smaller than that of the non-invasive species(p<0.001).However,for the Poaceae plants,the genome of invasive species(19 species)was 2.138±0.237 pg,and that of non-invasive species was 2.915±0.069 pg,with no significant difference between the two.2.On the basis of 5694 known genome size of angiosperms,class I and class II and class III endangered species of endangered species genome size mean respectively 4.688 pg,4.157 pg,8.781 pg,we found endangered highest level(class III)genome size extremely significantly greater than the endangered species(type I),and endangered level lower species genome size(class II)(p < 0.001),the value of C-DNA has the same rule.For Orchidaceae plants,the mean genome sizes of class I species,class II endangered species and class III endangered species were 4.410 pg,12.612 pg and 19.718 pg,respectively.The mean values of DNA c-values of endangered plants of class I,II and III were 4.518 pg,12.613 pg and 23.622 pg,respectively.Therefore,in groups with similar genetic backgrounds,endangered species also have larger DNA c-value and genome size.3.Among 735 Poaceae plants in the world,the average genome size of diploid(267 species)and polyploid(468 species)was 3.383 ± 0.128 pg and 2.661 ± 0.076 pg,respectively,and we found that the genome size of diploid was significantly larger than that of polyploid(p<0.001).We analysis the genome size of Poaceae plants within the scope of Australia,founding the same rule?We analysis the differences of the genome size between the different ploidy of Poaceae plants,founding their genome size is very significant different,and the diploid has the biggest genome size,and the mean genome size of the dodecaploid is the smallest.4.There are 54,395 known poaceae sites in the world.The DNA c-values of diploid,tetraploid,hexaploid and octaploid obtained by Feulgen microdensity method were 3.826±0.017 pg,3.157±0.015 pg,2.206±0.017 pg and 2.543±0.016 pg,respectively.The DNA c-values of diploid,tetraploid,hexaploid and octaploid obtained by flow cytometry were 1.726 ± 0.012 pg,2.243 ± 0.020 pg,2.229 ± 0.140 pg,and 2.020 ±0.020 pg,respectively.There are 2889 known poaceae sites in Australia.The DNA cvalues of diploid,tetraploid,hexaploid and octaploid obtained by Feulgen microdensity method were 4.697±0.086 pg,3.315±0.063 pg,2.177±0.077 pg and 2.990±0.000 pg,respectively.The DNA c-values of diploid,tetraploid,hexaploid and octaploid obtained by flow cytometry were 1.637±0.047 pg,2.156±1.648 pg,2.055±0.036 pg,and 2.055±0.008 pg,respectively.We found that there was a significant difference in DNA cvalue between diploid,tetraploid and octaploid species determined by the two methods(p<0.05),while there was no significant difference in hexaploid.5.The DNA 2C values of domestic Echinochloa and its varieties,e.cruspavonis,e.glabrescens and e.calum(linn.)Link were 2.319 0.010 pg,2.252 0.043 pg,2.297 0.024 pg and 2.170 0.025 pg,respectively.There was a certain degree of variation of DNA 2C value among the Echinochloa species(p = 0.113).The DNA 2C values of E.crusgalli?E.crusgalli var.breviseta ? E.crusgalli var.mitis ? E.crusgalli var.zelayensis ?E.crusgalli var.praticola were 2.357±0.025 pg ? 2.331±0.037 pg ? 2.305±0.010pg?2.309±0.024pg?2.412±0.027pg?There was no significant difference in DNA 2C value between different varieties of Echinochloa grass(p =0.370),and the difference was smaller than that between different varieties.We combine our predecessors on the testing data tares of 36 samples,to barnyard grass as a whole,the DNA 2C-value(y)with latitude(x1)and longitude(x2)are showed regular changes,using gaussian model and linear model fitting respectively,but the application of gaussian model can better fit the nonlinear methods DNA 2C value and the relationship between geographical gradient.The DNA 2C value of Echinochloa was higher at latitude 29°,and showed a downward trend with the increase or decrease of latitude.On the longitude gradient,the DNA 2C value of Echinochloa was higher at longitude 114°,and the DNA 2C value showed a downward trend as the longitude increased or decreased.At the level of species,the DNA 2C value of Echinochloa,its varieties and E.cruspavonis also showed the above trend,but the geographical latitude of the DNA 2C value of E.glabrescens was not obvious.6.The effect of latitude on the size of plant genome was analyzed by quantile regression.On a global scale,there was a significant non-linear relationship between the genome size and latitude of Poaceae and leguminous herbs,indicating that the DNA 2C value of these groups was smaller at the equator and nearby regions,and increased towards higher south and north latitudes.In the northern hemisphere,DNA 2C value reaches its maximum value at latitude 55 degrees.With the further increase of latitude,this value shows a downward trend.Quantile regression analysis shows that species with large genomes are less distributed near the equator and in high latitudes and more distributed in middle latitudes,while species with small genomes are distributed in the whole latitudes.This indicates that species with small genomes can adapt to more severe or diverse environmental conditions,that is,environmental conditions have a selective effect on genome size.7.On the global scale,with quantile regression analysis method,we statistically analysised the effects on plant genome size by different climate factors,founding that within the scope of the global large-scale,it is obvious nonlinear relationship between Poaceae,leguminosae herbage plant and climate factors,but obvious linear relationship between Asteraceae,leguminosae woody and climate factors.In different loci,the degree of influence of climate factors on the content of plant nuclear DNA is different.It is found that climate factors have a greater influence on species with larger genome size,that is,species with larger genome have higher requirements for living environment,while species with smaller genome have distribution in the whole climate.8.Based on the nuclear DNA content of monocotyledon plants in ten latitudinal gradients around the world,the variation of nuclear DNA content of monocotyledon plants along latitudinal gradients was analyzed.On the global scale plant nuclear DNA contents varied nonlinearly with latitude,the values being lowest in the regions around the equator or those near the Arctic,and being highest in the temperate mid-latitude regions;the values were affected by climatic factors,which were highest in the regions with moderate temperature and rainfall,and decreased in the environment of extreme temperature and rainfall,the relationships between plant nuclear DNA values and climatic factors also being nonlinear,following "unimodal" functions;the groups with lower nuclear DNA values distributed widely on the global scale,while those with higher nuclear DNA values distributed more frequently in the temperate mid-latitudes,revealing restrictive influences of extreme climate environments on the distribution of the species with higher nuclear DNA values.Therefore,plant nuclear DNA contents changed regularly and nonlinearly with latitude on the global scale,which was of strong adaptation significance to climatic environments.9.We analysised the relationship between angiosperms and surface nitrogen content in Australia,revealing that there was a significant non-linear relationship between the nitrogen conten and the genome size t of Asteraceae,and a significant linear relationship between the nitrogen content and genome size of Leguminous woody plants.Species with smaller genome size distributed in all the nitrogen content,species with larger genome size distributed more under the condition of less nitrogen.When nitrogen content rose to a certain value,species with large genome size were basically not distributed,indicating that surface nitrogen content had a greater impact on plants with large genome size.10.Analysis the differences of genome size between Poaceae plants with different groups and different species evolution by the mean of one-way anova of SPSS,finding that the genome sizes of the genera with different evolutionary degrees of Poaceae have significant differences,and the genome size of species with different evolutionary degrees within the same genus also varies to some extent. |
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