Investigating KNOX Gene Expression in Aquilegia Petal Spur Development

(1) Cambridge Rindge and Latin High School, Cambridge, Massachusetts, (2) Organismic and Evolutionary Biology Department, Harvard University, Cambridge, Massachusetts

Organ growth in many flowering plants progresses through two phases: cell proliferation and cell elongation. Recent work has indicated that class 1 KNOX genes regulate cell proliferation. These genes encode transcription factors that are largely responsible for a steady supply of undifferentiated stem cells. Moreover, KNOX gene expression is detectable in lateral organs of different plants such as compound leaves, suggesting a role in sculpting organ shape. The association of KNOX genes with stem cells suggests a role for these genes in the cell division phase of plant development. This suggests that a specific lateral organ, petal spurs, may be built in part using KNOX genes. Indeed, previous work has shown that KNOX gene over-expression in petals may cause spur-like outgrowths. In Aquilegia, a short proliferation phase gives rise to nascent spurs, which is followed by a cell elongation phase. We investigated KNOX gene expression and found by using Reverse Transcription Polymerase Chain Reaction, that expression of KNOX genes was detectable, but not uniformly so, suggesting that there may be either a highly cell-specific expression of KNOX genes or extremely low expression in petal spurs. Future tests with micro dissected tissue samples may prove to be helpful but it can be concluded for now that KNOX genes are not highly or consistently expressed in Aquilegia petal spurs, and their role in this organ is an ongoing mystery.

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