{Reference Type}: Journal Article
{Title}: Unique features of conventional and nonconventional introns in Euglena gracilis.
{Author}: Gao P;Zhao Y;Xu G;Zhong Y;Sun C;
{Journal}: BMC Genomics
{Volume}: 25
{Issue}: 1
{Year}: 2024 Jun 13
{Factor}: 4.547
{DOI}: 10.1186/s12864-024-10495-9
{Abstract}: <B>BACKGROUND: </B>Nuclear introns in Euglenida have been understudied. This study aimed to investigate nuclear introns in Euglenida by identifying a large number of introns in Euglena gracilis (E. gracilis), including cis-spliced conventional and nonconventional introns, as well as trans-spliced outrons. We also examined the sequence characteristics of these introns.<BR><B>RESULTS: </B>A total of 28,337 introns and 11,921 outrons were identified. Conventional and nonconventional introns have distinct splice site features; the former harbour canonical GT/C-AG splice sites, whereas the latter are capable of forming structured motifs with their terminal sequences. We observed that short introns had a preference for canonical GT-AG introns. Notably, conventional introns and outrons in E. gracilis exhibited a distinct cytidine-rich polypyrimidine tract, in contrast to the thymidine-rich tracts observed in other organisms. Furthermore, the SL-RNAs in E. gracilis, as well as in other trans-splicing species, can form a recently discovered motif called the extended U6/5' ss duplex with the respective U6s. We also describe a novel type of alternative splicing pattern in E. gracilis. The tandem repeat sequences of introns in this protist were determined, and their contents were comparable to those in humans.<BR><B>CONCLUSIONS: </B>Our findings highlight the unique features of E. gracilis introns and provide insights into the splicing mechanism of these introns, as well as the genomics and evolution of Euglenida.