Academic Staff - Dr Mary Byrne

Research Areas

My lab is interested in regulation of plant development and for our studies we use the model species Arabidopsis thaliana. Our research focuses on plant shoots and covers three main areas.

Left: Scanning electron micrograph of a vegetative shoot apex showing shoot meristem and young developing leaves. Right: Adaxial and abaxial sides of an Arabidopsis leaf.

Genes that control plant shoot meristems

Plant shoot and root meristems are indeterminate structures that are established in embryogenesis and give rise to the entire body of the plant. The shoot meristem has two functions. A population of undifferentiated stem cells are required to maintain the meristem for further growth. Cells derived from this stem cell population are recruited to form differentiated structures of the plant such as leaves. Gene networks are involved in maintaining the difference between stem cells of the meristem and differentiated cells of lateral organs. We have identified key components of this network and demonstrated negative regulatory interactions between the meristem homeodomain transcription factor class I KNOX genes and the lateral organ Myb domain transcription factor gene ASYMMETRIC LEAVES1 (AS1).

Left: Vegetative rosette of Arabidopsis wild type and as1 mutant. Middle: Complementary expression domains of AS1 and the KNOX gene STM. Right: Graphical representation of the shoot apex; AS1 in leaves represses KNOX expression and KNOX in the meristem represses AS1.

Molecular basis of leaf patterning

Leaves initiate on the flanks of the shoot meristem and the mature leaf forms through patterning in three planes. (1) Dorsoventral polarity establishes distinct adaxial (top) and abaxial (bottom) sides of the leaf. (2) Outgrowth of the leaf from the meristem establishes proximodistal polarity, corresponding to the base and tip of the leaf. (3) Growth of the leaf lamina from the central midvein to the margin of the leaf sets up mediolateral polarity. Dorsoventral polarity, or specification of adaxial and abaxial domains, is essential for development of leaf lamina. Likewise, adjacent adaxial and abaxial domains can lead to ectopic leaf lamina. Genes regulating dorsoventral polarity include transcription factor genes and genes involved in production of small RNAs. We have made the surprising discovery that ribosomal protein genes, called PIGGYBACK (PGY) genes, are also required for dorsoventral patterning of the leaf.

Left: as1 pgy mutant leaf with ectopic lamina outgrowths on the adaxial side of the main leaf. Right: Scanning electron micrographs of developing ectopic lamina outgrowths in as1 pgy mutant.

The role of ribosomes in plant development

Life is maintained through a central chain of events from DNA to mRNA to proteins. Translation of mRNA into proteins is carried out by the ribosome. In eukaryotes ribosomes are composed of a small and a large subunit, together consisting of 3 RNA molecules and nearly 80 proteins. Although the ribosome is involved in protein synthesis we have found that mutations in ribosomal proteins have discrete developmental phenotypes. How this occurs is currently unknown. However, our work on pgy ribosomal protein mutants is providing information that ribosomal proteins have a greater role in eukaryote development than previously assumed and raises the possibility that a basic cellular housekeeping process has a broader function and is a control point for developmental patterning in plants.

Publications in Plant Development

• Szakonyi, D., Moschopoulos, A. and Byrne, M.E. (2010). Perspectives on leaf dorsoventrality. Journal of Plant Research 123:281-290.
  Citations: 0.
• International Brachypodium Initiative. (2010). Genome sequencing and analysis of the model grass Brachypodium distachyon Nature 463:763-768.
  Citations: 5.
• Byrne, M.E. (2009). A role for the ribosome in development. Trends Plant Science 9:512-9.
  Citations: 1.
• Wu C., You C., Li C., Long T., Chen G., Byrne M.E. and Zhang Q. (2008). RID1, encoding a Cys2/His2-type zinc finger transcription factor, acts as a master switch from vegetative to floral development in rice. Proceedings of the National Academy of Science USA 105:12915-1292.
  Citations: 14.
• Pinon V., Etchells J.P., Rossignol R. Collier R.A., Arroyo J.M., Martienssen R.A. and Byrne M.E. (2008) Three PIGGYBACK genes specifically influencing leaf patterning encode ribosomal proteins. Development 135:1315-1324.
  Citations: 17.
• Byrne M.E. (2006). Shoot meristem function and leaf polarity: the role of class III HD–ZIP genes. PloS Genetics 2: e89.
  Citations: 13.
• Garcia D., Collier S.A., Byrne M.E., Martienssen R.A. (2006). Specification of leaf polarity in Arabidopsis via the trans-acting siRNA pathway. Current Biology 16: 933-938. (corresponding author).
  Citations: 89.
• Byrne M.E. (2005). Networks in leaf development. Current Opinion Plant Biology 8: 59-66.
  Citations: 25.
• Byrne M.E. (2005). Shoot development – genetic interactions in the meristem. Biochemical Society Transactions 33: 1499-1501.
  Citations: 2.
• Byrne M.E., Kidner C.A. and Martienssen, R.A. (2003). Plant stem cells: divergent pathways and common themes in shoots and roots. Current Opinion in Genetics and Development 13: 551-557.
  Citations: 18.
• Byrne M.E., Groover A.T., Fontana J.R. and Martienssen R.A. (2003). Phyllotactic pattern and stem cells fate are determined by the Arabidopsis homeobox gene BELLRINGER. Development 130: 3941-3950.
  Citations: 56.
• Kidner C.A., Timmermans M.C.P., Byrne M.E. and Martienssen R.A. (2002). Developmental genetics of the angiosperm leaf. In Advances in Botanical Research: Volume 38 (ed. J. A. Callow), pp. 191-234. London: Academic Press.
  Citations: 5.
• Byrne M.E., Simorowski, J. and Martienssen, R.A. (2002). ASYMMETRIC LEAVES1 regulates knox gene redundancy. Development 129: 1957-1965.
  Citations: 142.
• Byrne M., Timmermans M., Kidner C. and Martienssen R.A. (2001). Development of leaf shape. Current Opinion in Plant Biology 4: 38–43.
  Citations: 43.
• Byrne M.E., Barley R., Curtis M., Arroyo J.-M., Dunham M., Hudson A. and Martienssen R.A. (2000). Asymmetric leaves1 mediates axis leaf patterning and stem cell fate in Arabidopsis. Nature 408: 967-71.
  Citations: 290.