Two new SINE elements, p-SINE2 and p-SINE3, from rice

Area of Science:

• Genomics and Molecular Evolution
• Plant Genetics
• Bioinformatics

Background:

• Short interspersed nuclear elements (SINEs) are mobile genetic elements found in eukaryotic genomes.
• p-SINE1 elements have been identified in various rice species (Oryza sativa) with different genomes (AA or non-AA).
• The evolutionary history and genomic distribution of rice SINEs are not fully understood.

Purpose of the Study:

• To identify and characterize novel SINE families in rice.
• To investigate the evolutionary relationships and origins of different rice SINE families.
• To analyze the genomic distribution and potential functional implications of these SINEs.

Main Methods:

• Bioinformatic analysis of rice genomic sequences to identify novel SINE elements.
• Sequence comparison and homology analysis to determine relationships between SINE families.
• Phylogenetic analysis to infer evolutionary origins.
• Comparative genomics to assess the distribution of SINEs across different rice species and genomes.

Main Results:

• Two new rice SINE families, p-SINE2 and p-SINE3, were identified, distinct from p-SINE1.
• p-SINE2 and p-SINE3 share homology with p-SINE1 in their 5' regions (promoter elements) but differ in 3' regions, though all possess a conserved stem-loop structure and T-rich tail.
• p-SINE2 and p-SINE3 are dispersed across rice chromosomes, preferentially in gene-rich areas, with p-SINE2 found in AA, BB, CC, DD, and EE genomes, while p-SINE3 is specific to the AA genome.
• Sequence divergence suggests p-SINE1 is older, and p-SINE2 and p-SINE3 likely evolved from it.

Conclusions:

• The three rice SINE families (p-SINE1, p-SINE2, p-SINE3) likely originated from a common ancestor.
• p-SINE2 and p-SINE1 share a broader evolutionary history across multiple rice genomes, while p-SINE3 appears to have a more recent origin within the AA genome lineage.
• The conserved RNA secondary structure in the 3' region suggests functional importance in retroposition, and the differential distribution indicates distinct evolutionary trajectories.