Developmental Biology of Dormancy Cycling

In perennial plants, like trees, the SAM is cycling between active and dormant states in synchrony with the season (Rinne et al. 2001; Rinne and van der Schoot 2003, 2004). The SD-induced development of dormancy and acclimation involves the obstruction of cellular contacts at the SAM, including both Pd and cell walls (Rinne et al., 2001; Rinne and van der Schoot 2004). The present proposal is necessary to continue part of the NFR-funded strategic university project ?Climatree? (2003-2007). This part, whic h is ending at the beginning of 2006, has generated important insights. In birch, SD induces the development of dormancy sphincter complexes (DSC) that close all Pd, cell walls become water-repellent, and ER-derived lipid bodies (spherosomes) are randomly produced in the cytoplasm. The lipid bodies possess 8 unidentified proteins, among which 1,3-b-D-glucanase (GLU-h). During chilling-induced dormancy breaking the lipid bodies are displaced towards cell membrane and Pd, while DSC disappear. As DSC contain 1,3-b-D-glucan (GLU), the physical contact between lipid bodies and the DSC may facilitate GLU-h driven hydrolysis of GLU, thereby restoring Pd. In addition, lipid bodies may recycle membrane lipids and deliver additional proteins to the membrane and wal l. We here aim to further investigate the proteome of the lipid bodies by isolating the proteins, and identify the genes that encode for them. We will investigate the function of these proteins by using RNA silencing technology and overexpression studies. In addition, microarrays will be used to pinpoint genes in the dormancy related pool that might function in the control over Pd function during dormancy cycling. We will use Birch and Arabidopis as model plants. Understanding dormancy cycling is importan t to design optimal strategies for forestry and plant production in geographically distinct areas, particularly in view of the deregulating effects of global climate changes.