POLLEN SPECIFICITY ELEMENTS RESIDE IN 30 BP OF THE PROXIMAL PROMOTERSOF 2 POLLEN-EXPRESSED GENES

Functional analyses previously identified minimal promoter regions req uired for maintaining high-level expression of the late anther tomato LAT52 and LAT59 genes in tomato pollen. Here, we now define elements t hat direct pollen specificity. We used a transient assay system consis ting of two cell types that differentially express the LAT genes and b oth ''loss-of-function'' and ''gain-of-function'' approaches. Linker s ubstitution mutants analyzed in the transient assay and in transgenic plants identified 30-bp proximal promoter regions of LAT52 and LAT59 t hat are essential for their expression in pollen and that confer polle n specificity when fused to the heterologous cauliflower mosaic virus 35S core promoter. In vivo competition experiments demonstrated that a common trans-acting factor interacts with the pollen specificity regi on of both LAT gene promoters and suggested that a common mechanism re gulates their coordinate expression. Adjacent upstream elements, the 5 2/56 box in LAT52 and the 56/59 box in LAT59, are involved in modulati ng the level of expression in pollen. The 52/56 box may be a target fo r the binding of a member of the GT-1 transcription factor family.