This project is focused on understanding how plant organs grow and attain their final shape. In particular, this work is focused on the growth of petals in the plant Arabidopsis thaliana. Petals are excellent organs for studies such as these because they are accessible and are not essential for plant reproduction. In particular, this project will examine the role of two genes that function to control petal growth. The first gene is a micro-RNA gene (miR319a) that functions by regulating a set of DNA binding transcription factor genes of the TCP family. The second gene, named DORNRÖSCHEN-LIKE (DRNL), is a DNA binding transcription factor. When either the miR319a or DRNL gene is inactivated, the petals develop, but do not attain the normal shape. However, when both miR319a and DRNL are inactivated together, the petals are reduced to very small filamentous structures. The work in this project is focused on understanding how the genetic and molecular pathways controlled by miR319a and DRNL function together to control the growth of petals.
This project has several broader impacts. First, this work is important because it will contribute to our knowledge about how plant organs attain their shape. A more detailed understanding of plant growth in petals will increase our knowledge of the growth of more agriculturally important plant organs such as leaves, fruits, and seeds, three key components of the human diet. Second, this project will provide training for several graduate students and undergraduate students. Third, the primary outreach activity of this project involves participation in a summer professional development workshop for high school teachers from Vermont and New Hampshire, many of whom are from under-resourced public schools.
This project focused on understanding the molecular mechanisms that underlie how plant organs are specified, how they grow, and how they attain their final shape. In particular, this work focused on the floral organs in the plant Arabidopsis thaliana. The Arabidopsis flower, like most angiosperm flowers, consists of four organ types: sepals, petals, stamens, and carpels. This project focused on several genes that play key roles during the early stages of flower development. The first gene is a micro-RNA gene (miR319a) that functions by regulating a set of DNA binding transcription factor genes of the TCP family. When miR319a function is impaired, the petals are small and misshapen and the six stamens, which normally develop as separate organs, fuse together. A second gene, named DORNRÖSCHEN-LIKE (DRNL), encodes a DNA binding transcription factor. When DRNL function is impaired, the stamens most often do not form due to a failure of stamen primordia to properly enlarge and differentiate. A third gene, SUPERMAN, functions to repress other genes. When SUPERMAN function is impaired, extra stamens and fewer carpels develop in the flower. There are two major scientific outcomes of this work. First, we demonstrated, using live confocal imaging, that DRNL is expressed in the precursor founder cells for all of the floral organs. Early in flower development, DRNL marks the positions where the stamens will develop; surprisingly, the plant hormone auxin does not direct responses during these stages of stamen development suggesting that DRNL may be more important than auxin for stamen primordia formation. Second, we demonstrated, using live confocal imaging, that the additional stamens that develop in superman mutants derive from cells in the floral meristem, and not from cells in the third whorl where SUPERMAN is expressed as had been previously postulated. This project has several broader impacts. First, this work is important because it has contributed to our knowledge about how plant organs are specified, grow, and attain their final shape. These insights into floral organ growth in Arabidopsis can easily be extrapolated to crop plants, and thus lead to an increase our knowledge of the growth of plant organs such as leaves, fruits, and seeds in agriculturally important plants. Second, this project provided training for postdoctoral fellows, graduate students and undergraduate students. Third, the primary outreach activity of this project involved participation in hands-on workshops here at Dartmouth for K-12 students from Vermont and New Hampshire, many of whom are from under-resourced public schools.
