Leaf polarity and growth factors play important roles in patterning the fruit in Arabidopsis

Seed dispersal facilitated by the fruit is dependent on the formation of a specialized stripe of tissue termed the valve margin, which enables the valves to detach from the fruit and disclose the seeds. Valve margin development is dependent upon the SHATTERPROOF (SHP) genes and is limited to a stripe of cells through the repressive activities of FRUITFULL (FUL) in the valves and REPLUMLESS (RPL) in the replum. A critical aspect of fruit development that is not well understood is how the patterns of gene activities that control valve margin formation are initially established. We have found that FILAMENTOUS FLOWER (FIL) and YABBY3 (YAB3), genes which regulate the polarity of tissues in lateral organs, are required to promote the expression of FUL and SHP. The unrelated gene, JAGGED (JAG), which promotes the growth of tissues in lateral organs, acts redundantly with FIL and YAB3 to promote the expression of FUL and SHP, with jag fil yab3 triple mutants lacking FUL and SHP expression in the valves or valve margins. We also provide insight into the mechanism by which RPL regulates valve margin development by showing that RPL negatively regulates JAG/FIL activity in the replum. Our work describes the first functional link between patterning systems in plants that define organ polarity and growth and those that control tissue identity and provides a genetic framework for the patterning of the three tissue types composing the fruit