Effects Of Heterozygosity And Stress On Plant Mutation And Recombination

Mutations and recombinations have important implications in evolution.They are the main forms of inherited variations and have long been frontier areas in biology.Mutations,either SNP or indel,distribute extremely unevenly along the genome,most of which cluster in hotspots.It has been suggested that mutation hotspot is associated with neucleotide compositions or special epigenetics modifications.Based on genome comparison,our team previously proved that SNP mutation frequency will increase near indel loci,so we suggested that indel may have mutation inducing effect.Mutation rate and recombination rate of the sam species rarely surpass the range while raised in natural conditions,however,if under stress conditions,both recombination rate and mutation rate may increase significantly.Recombination also cluster in hotspots while there are cold spots where recombination rarely occurs.As the next generation of sequencing develops,we could derectly sequence multiple progenies of a single generation and take the information of all the mutation and recombination on a genome scale.We hope to investigate the effects of heterozygosity and stress on plant mutation and recombination.Frist,we suggested that heterogeneous site have a mutator effect to the local region.We sequenced the progenies of heterozygous and homozygous plants and compare their mutation rate.The result shows that heterozygous plants indeed have higher mutation rate than homozygous plants.The mutation rate decreases while heterozygosity decreases and in a single plant,the heterogeneous part of the genome has higher mutation rate than the homozygous part.Second,to test whether stress could increase mutation rate and recombination rate,we sequenced progenies raised under stress conditions and compare their mutation rate and recombination rate with progenies raised under natural conditions.The result suggests that UV radiation,high temperature and pathogen infection could increase the mutation rate and recombination rate of some progenies.But the extent is limited and not all progenies have this effect.We also come out with a map of rice recombination.In rice more than 9.1%recombination events occurred in hotspot regions less than 0.72%of the genome.Most of the recombination cold spots were around the pericentromeric region.In this study we proved that heterozygosity could increase mutation and this could help in the explanation of mutation hotspot in the genome.We also proved that enviroment stress could directly influence mutation rate and recombination rate other than just having a selection effect on the organisms.The recombination map of rice would be beneficial in the breeding of rice cultivars.