Control of plant shape

Abstract

In the past years, the establishment of body shape and Bauplan in animals has been shown to be based upon a spatiotemporal pattern in the activity of transcription factors. The discovery of homeotic genes controlling flower morphogenesis stimulated the view that plant morphogenesis might follow the same principles. Based on this idea, a mutant approach was initiated to screen for pattern deletion mutants in Arabidopsis. Interestingly, the characterization of these mutants lead not to the isolation of the anticipated transcription factors, but to genes that are related to the formation of the cell plate. This outcome moves the spatiotemporal control of cell division into the centre of interest. Plants have developed microtubular structures that seem to be intimately linked to the spatial control of cell division: radial microtubules, preprophase band, and phragmoplast. This chapter will begin with a brief discussion of the impact of plant shape and then discuss the control of division axis and symmetry in cell biological terms. This will be followed by a discussion of potential molecular mechanisms related to this spatial control. A second role of microtubules during the control of plant shape is connected to their participation in mechano and gravity sensing. The prospect part of the chapter will treat, in a speculative way, the possibilities to manipulate gravitropic set-point angles and thus the angle of side branches (e.g. to increase photosynthetic efficiency), but also the control of phyllotaxis (whorl pattern), root architecture and tuber formation (in potatoes).