Research Of Plant Intron Evolution Pattern

Considerable debate remains over several years and aspects of the evolution of spliceosomal introns, a major class of genetic element, including the timing of intron origin and proliferation, the mechanisms by which introns are lost and gained, and the forces that have shaped intron evolution. After entered into the genomic era, research of the spliceosomal intron evolution has been extremely actived by the mass genome sequences; however, plant intron study has just begun.Here we carry out a large-scale analysis on introns in different plant species, and the results are as follows:1．We measure the intron location and length profiling in 32 plant species, that average intron length in plant is shorter than in animal, even in some huge genome size plant lineages. We estimate that a remarkable difference in intron density exist between algae and higer plants.2．Analysed with our new intron gain/loss detect algorithm, the results underscore that low intron gain rates and intron number reduction are common features of recent plant evolution. We also find high intron gain rates in few species. We observe that most of intron positions are conserved in higher plants, some of them shared with algae. This pattern implies that rates of intron creation were high during earlier periods of plant evolution and algae have been a lot of intron loss.3．To gain insight into the forces that control intron evolutione and its impact for the intron length and intron loss, we test the relationship between gene expression and intron profiling. The results show that intron length and intron loss are affect with different factors, they are independence.4．We observe that intron change rates among paralog genes are higher than among ortholog genes in rice and arabidopsis, rate between intron loss and gain is 2:1．Moreover, tandem duplication genes show more intron gains, rate between intron loss and gain is almost 1:1．This result suggests that gene duplication may active intron gain and loss. 5．Glycine max,Triticum aestivum and Zea mays, which with actively transposons, have high intron gain rates in their genus. Further sequence analysis of new gained intron shows most of these introns have similar sequence with transposon, implies that new intron may create with transposon insertion.6．Thalassiosira pseudonana and Chlamydomonas reinhardtii have large number of species-specific intron position. Through comparing with a variety of alage intron position, we confirm that these two lineages have passed through a very intron-poor stage since early plant evolution and gained large number of intron in recent evolution.7．Based on above results, we developed a database of potential intron polymorphism (PIP) markers.8．In addition we advance a proposal about intron evolution: intron gain and loss are independent progress, intron loss rates might simply be rate of evolution, gain rates might be tiered with transposon and recombination rates in genome.