Researchers Explain Key Developmental Mechanism in Plants for the First Time

Researchers from the Cold Spring Harbor Laboratory (CSHL) led by Prof. Marja Timmermans have explained for the first time a mechanism in plants that controls a group of key developmental regulatory genes called homeobox genes.The homeobox genes studied by the group are BREVIPEDICELLUS (BP) and KNAT2. These genes have to be active in plant stem cells for the cells to maintain their non-specialized character. Stem cells develop, or "differentiate," into any plant cell type, depending only on signals that they receive, which send them down the developmental path. When the moment is just right for plant organs such as leaves to begin to grow, BP and KNAT2 are switched off so that development can proceed. A highly conserved assembly of proteins, called Polycomb-repressive complex2 (PRC2), spurs a process called epigenetic regulation that physically marks targeted genes – in this case, BP and KNAT2 – for repression.

Professor's Timmermans' team showed that PRC2 physically interacts with DNA binding proteins that attach to plant DNA in specific genome regions just ahead of where the homeobox genes are situated. In the plant they studied, Arabidopsis, those DNA binding proteins are ASYMMETRIC LEAVES1 (AS1) and AS2. When a stem cell commits to becoming a leaf cell, AS1 and AS2 become active, attach at the DNA sites near BP and KNAT2, and recruit PRC2 to repress these homeobox genes. The epigenetic mark made by PRC2, which acts like a cellular memory, is heritable, and is essential in order for leaves and other plant organs to develop.

Results of the team's study is published in the March 6 issue of Genes and Development and the abstract can be viewed online at http://genesdev.cshlp.org/content/early/2013/03/04/gad.211425.112.abstract. The news release can be read at http://www.cshl.edu/Article-Timmermans/researchers-explain-a-key-developmental-mechanism-for-the-first-time-in-plants.