The establishment of the cambium-specific stem cell niche, which is being addressed by characterizing CBI1, a novel repressor of cambium identity in Arabidopsis thaliana

• Applicant: Dr. Stefanie Suer
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2012 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 215904443

The vascular cambium, being an essential tissue for plant biomass production, is of extraordinary importance for plant growth and current plant research, and represents a unique system to study meristem regulation. Interestingly, despite the well-established connection between the plant hormone auxin and the promotion of cambium initiation and activity, a molecular link on the level of the cambium itself has only recently been described by the transcription factor WOX4 (Suer et al., 2011). In this project, we will make use of CAMBIUM ISLANDS1 (CBI1), a novel locus involved in WOX4 regulation to address the question of how cells establish meristematic activity, upstream of WOX4. We identified cbi1 mutants in a forward genetics screen for mutants with altered activity of a WOX4:GUS reporter. Represented by two recessive alleles, cbi1 mutants display island-like ectopic WOX4:GUS activity in the pith tissue of stems, overlapping with cellular patterning defects. Furthermore, cbi1 stems show enhanced transcript levels of the (pro)cambium-specific genes ATHB8, PXY, and WOX4, and the auxin-inducible genes PIN1 and IAA5, suggesting a general role of CBI1 in repressing the entire program of cambium identity. Based on these observations, I hypothesize that CBI1 functions upstream of auxin biosynthesis, transport, or signaling. Because such a general vascular regulator has so far not been described, revealing the function of CBI1 within the network of known cambium regulators will be highly significant. By detailed mutant analysis on both histological and molecular levels, identification of the CBI1 locus, subsequent expression studies, and by unraveling the connection of CBI1 with auxin biosynthesis, transport, and signaling, the project has the potential to deliver long-sought insights into the early events of vascular patterning and cell specification.

• DFG Programme: Research Fellowships
• International Connection: Austria
• Host: Professor Dr. Thomas Greb