Transcripts of Vp-1 homoeologues are alternatively spliced within the Triticeae tribe

Hexaploid bread wheat (Triticum aestivum) caryopses are characterised by relatively weak embryo dormancy and display pre-harvest sprouting (PHS) under cool moist conditions. The phenotype of sprouted wheat is very similar to that of the maize seed-specific mutation viviparous 1 (vp1) and to abi3 in Arabidopsis. VP1 has been shown to be a transcription factor that functions both in the activation of genes involved in the maturation program and in the repression of genes involved in germination. Our analysis of the three wheat Vp-1 gene homoeologues has shown that each gene produces a set of cytoplasmic mRNAs, the majority of which are alternatively spliced, containing unedited intron sequences and deletion of coding region. These transcripts do not have the capacity to encode full-length proteins. The analysis of these Vp-1 transcripts has been extended to look at their structure in the presumed progenitors of wheat and species within the triticeae tribe, which may allow us to determine when alterations in transcript structures evolved. Results using transgenic plants have shown that expression of the Avena fatua VP1 protein in wheat has a positive effect in the reduction of PHS. In addition, there was a clear reduction in the germination indices of transgenic seeds compared to the control under conditions that would promote PHS.