title: Spaceflight-induced genetic and epigenetic changes in the rice (Oryza sativa L.) genome are independent of each other.
abstract: An array of studies have reported that the spaceflight environment is mutagenic and may induce phenotypic and genetic changes in diverse organisms. We reported recently that in at least some plant species (e.g., rice) the spaceflight environment can be particularly potent in generating heritable epigenetic changes in the form of altered cytosine methylation patterns and activation of transposable elements. To further study the issue of spaceflight-induced genomic instability, and in particular to test whether the incurred genetic and epigenetic changes are connected or independent of each other, we performed the present study. We subjected seeds of the standard laboratory rice (Oryza sativa L.) cultivar Nipponbare to a spaceflight in the spaceship Long March 2 for 18 days. We then investigated the genetic and DNA methylation stabilities of 11 randomly selected plants germinated from the spaceflown seeds by using two kinds of DNA markers, amplified fragment length polymorphism (AFLP) and methylation sensitive amplified polymorphism (MSAP). For AFLP, by using 15 primer combinations, we assessed 460 genomic loci and found that the frequencies of genetic changes across the 11 plants ranged from 0.7% to 6.7% with an average frequency of 3.5%. For MSAP, by using 14 primer combinations, we assessed 467 loci and detected the occurrence of four major types of cytosine methylation alterations at the CCGG sites, namely CG or CNG hypomethylation and CG or CNG hypermethylation. Collectively, the frequencies of the two kinds of hypermethylation, CG (1.95%) and CNG (1.44%), are about two times higher than those of the two kinds of hypomethylation, CG (0.76%) and CNG (0.80%), though different plants showed variable frequencies for each type of alteration. Further analysis suggested that both the genetic and cytosine methylation changes manifested apparent mutational bias towards specific genomic regions, but the two kinds of instabilities are independent of each other based on correlation analysis.
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun 130024, China.
authors.forename: Xiufang
authors.initials: X
authors.lastname: Ou
authors.forename: Likun
authors.initials: L
authors.lastname: Long
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Yu
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Lin
authors.forename: Xin
authors.initials: X
authors.lastname: Qi
authors.forename: Bao
authors.initials: B
authors.lastname: Liu
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D019175:DNA Methylation; D018744:DNA, Plant / Q000235:genetics; D044127:Epigenesis, Genetic; D018745:Genome, Plant / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D012275:Oryza / Q000235:genetics*; D013026:Space Flight
chemical_list: D018744:DNA, Plant