Regulated use of an alternative spliced leader exon in the plant parasitic nematode Meloidogyne javanica

In the nematodes Caenorhabditis elegans and Ascaris suum about 80% of messenger RNAs (mRNAs) have at their 5' end a short trans-spliced exon known as the spliced leader (SL). Trans-splicing has now been demonstrated in all nematode species examined suggesting that it is a universal feature of nematode gene expression. The addition of the SL appears to be linked to the generation of mature capped mRNAs and SL addition directs efficient translation in a homologous in vitro system. The sequence of the major spliced leader in different nematodes is apparently identical to the C. elegans SL1. Additional SLs have been described recently in C. elegans which differ in function from the first described and more abundant SL1. These SLs (SL2, SL3, SL4, SL5 and several others) are more related in sequence to each other than to SL1. They are trans-spliced to down-stream genes in operons and function in the resolution of polycistronic pre-mRNAs into monocistronic mature mRNAs. Here we describe for the first time the presence of two SL1-like SLs in a nematode, the plant parasite Meloidogyne javanica and present evidence that their use is developmentally regulated.