A STRONG INHIBITOR OF GENE-EXPRESSION IN THE 5'-UNTRANSLATED REGION OF THE POLLEN-SPECIFIC LAT59 GENE OF TOMATO

Promoter sequences that direct pollen-specific expression have been pr eviously identified in the LAT59 (for late anther tomato) gene. Here, we show that the LAT59 sequences encoding the 5' untranslated region i nhibit expression of reporter genes by >20-fold in transient expressio n experiments and up to 300-fold after stable transformation. Inhibiti on occurred in somatic cells as well as in pollen. Our results indicat e that the inhibitor still functions after pollen germination and ther efore does not modulate the level of the LAT59 protein during pollen d evelopment. The presence of the leader sequence dramatically decreased mRNA accumulation but without affecting translation rate and mRNA sta bility. We believe that the leader inhibits transcription. We mapped t he inhibitor to a region in the leader that coincides with a putative stem-loop and present evidence that this stem-loop participates in inh ibition.