PETAL LOSS

PTL-driven reporter gene expression was also detected at later stages in the margins of expanding sepals, petals and stamens, and in the leaf margins

Surprisingly, PTL expression could not be detected in petals during the early stages of their development

PTL transcripts were detected in the early-developing flower, in four zones between the initiating sepals and in their developing margins.

thus, PTL may redundantly dampen lateral outgrowth of these organs, helping define their final shape.

Strong misexpression of PTL in a range of tissues universally results in inhibition of growth, indicating that its normal role is to suppress growth between initiating sepals, ensuring that they remain separate.

Consistent with this, sepals are sometimes fused in ptl single mutants, but much more frequently in double mutants with either of the organ boundary genes cup-shaped cotyledon1 or 2.

so petal defects associated with PTL loss of function may be indirect, perhaps involving disruption to signalling processes caused by overgrowth in the region

We have cloned PTL and show that it encodes a plant-specific trihelix transcription factor

Perianth development is specifically disrupted in mutants of the PETAL LOSS (PTL) gene, particularly petal initiation and orientation.

Expression of PTL within the newly arising sepals is apparently prevented by the PINOID auxin-response gene.