Abstract
The introns are widely present in the genome of eukaryotes and the distribution of intron varies greatly among different organisms or different genes. Generally, introns loss is an important way for uneven distribution of intron during genome evolution. In this study, two closely related carnivorous plants (Genlisea aurea and Utricularia gibba) were chosen, their genome were relatively integrity and high quality, especially, the large difference in genome size between them. We detected intron loss events, then investigated the relationship between the genome size, intron density, intron loss and the mutation rate in the carnivorous plants. Finally, a total of 752 and 124 intron loss positions were identified in G. aurea and U. gibba, respectively. In carnivorous plants, we found that the region around lost site had high mutation rate, the genes of intron loss had high mutation rate. Besides, for the species with more intron losses, the genome size was smaller and the mutation rate was higher. Thus, we propose that the mutation rate was positively correlated with intron losses, but negatively correlated with intron number and genome size. These could be explained by the selection to minimize mutational hazards.
Highlights
The introns are ubiquitous in the eukaryotic genomes
We removed the introns with sequence length less than 30 bp and detected 62,377 and 88,915 satisfied introns in the annotation results of G. aurea and U. gibba, respectively
We identified 14,776 pairs of orthologous genes between the G. aurea and U. gibba, covering more than 80% of the genes in the G. aurea genome
Summary
The introns are ubiquitous in the eukaryotic genomes. the distribution of introns among different species and different genes are quite different (Ma et al, 2015b), studying the evolutionary dynamics of introns may provide clues to the evolution of eukaryotic genome. There is another way could change the frequency of alleles in the population, which is the mutation bias (Duret, 2008; Weber et al, 2014; Behringer and Hall, 2016) It means that, in the species, the probability of the beneficial mutation being fixed is higher than that of the neutral mutation, on the contrary, the probability of the disadvantage mutation being fixed is lower than that of the neutral mutation. A popular view about intron evolution is the mutational-hazard hypothesis proposed by Lynch He believes that non-coding sequences such as introns are harmful to organisms, but the power of these deleterious variations is very weak and is considered weakly harmful. In the species with samll Ne, the genetic drift plays a major role, such as eukaryotes, which cannot efficiently eliminate deleterious introns sequences and retain relatively high number of introns. Multicellular organisms have higher mutation rate and produce more mutations than unicellular organisms, and their genetic structure
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