ABSTRACT
The dynamic activity of transposable elements (TEs) contributes to the vast diversity of genome size and architecture among plants. Here, we examined the genomic distribution and transposition activity of long terminal repeat retrotransposons (LTR-RTs) in Arabidopsis thaliana (Ath) and three of its relatives, Arabidopsis lyrata (Aly), Eutrema salsugineum (Esa), and Schrenkiella parvula (Spa), in Brassicaceae. Our analyses revealed the distinct evolutionary dynamics of Gypsyretrotransposons, which reflects the different patterns of genome size changes of the four species over the past million years. The rate of Gypsy transposition in Aly is approximately five times more rapid than that of Ath and Esa, suggesting an expanding Aly genome. Gypsy insertions in Esa are strictly confined to pericentromeric heterochromatin and associated with dramatic centromere expansion. In contrast, Gypsy insertions in Spa have been largely suppressed over the last million years, likely as a result of a combination of an inherent molecular mechanism of preferential DNA removal and purifying selection at Gypsy elements. Additionally, species-specific clades of Gypsy elements shaped the distinct genome architectures of Aly and Esa.
Subject(s)
Brassicaceae/genetics , Evolution, Molecular , Genome Size , Genome, Plant , Genomics , Phylogeny , Retroelements , Species SpecificityABSTRACT
Objective To find new compound from soft corals.Methods The chloroform portion of the soft coral Sinularia sp.was subjected to silica gel to give ceramide(Ⅰ).Results Structure of compound(Ⅰ) was identified as 2S,3S,4R-N-octadecanoyl-phytosphingosine on the bases of spectroscopic(IR,MS,NMR) and chemical analyses.Conclusion Compound(Ⅰ) was a new natural ceramide and its IR, NMR data were reported here for the first time.