FIGURE 3.

Schematic representation of the splicing reaction in eukaryotes. 5′ and 3′ splice sites (SS) are recognized by SR proteins that attract the U1 and U2 snRNPs to constitute the intron defining complex. Then, the U4/U6.U5 tri-snRNP is recruited to the intron region to form the complex B. The exclusion of U1 and U4 snRNPs would rise to the complex B^∗ which, together with several RNA helicases, is responsible of the first and second catalytic reactions. These two reactions render the post-catalytic complex that contains the intron lariat, the ligated exons and the U4/U6.U5 tri-snRNP. The release of the snRNPs from this complex allows the regeneration of the spliceosome for subsequent splicing reactions. In green color are represented Arabidopsis proteins with known functions in plant tolerance to abiotic stress.