Besides the obvious longitudinal growth, plants also enlarge in the radial sense. This thickening of plant stems and roots provides physical support to plants, provides us with wood and cork, and plays a major role in sequestering atmospheric carbon into plant biomass. The tissues responsible for this radial expansion are the vascular tissues which transport water and nutrients around plants and are visible as concentric circles in tree trunks known as annual growth rings. Finally, radial growth is important for the production of many edible structures such as turnips, carrots, sugar beet and potatoes. Despite this obvious importance of lateral growth for both plant growth and our everyday lives, we know very little about how this process is controlled.
In two joint publications, De Rybel (VIB-UGent Center for Plant Systems Biology, Belgium) and Helariutta (SLCU, UK) research groups contribute to our understanding of plant radial growth by showing that several DOF-type transcription factors control oriented divisions in specific cells belonging to the vascular tissues called procambium cells.
Prof. Bert De Rybel (VIB-UGent): "Our results suggest that the seemingly homogenous set of cells in the procambium in fact contains distinct zones of high proliferation and strong quiescence depending on the position of the cell within the vascular bundle." While loss-of-function results in a dose-dependent loss of vascular cells, overexpression is able to trigger massive radial expansion by inducing oriented cell divisions in all cells in the root meristem. "This understanding will assist future breeding of economically important crops and trees to obtain higher yields and is able to improve atmospheric carbon sequestration by increasing plant biomass", adds De Rybel.
- Mobile PEAR transcription factors integrate hormone and miRNA cues to prime cambial growth, Miyashima et al., Nature 2018
- DOF2.1 controls cytokinin-dependent vascular cell proliferation downstream of TMO5/LHW, Smet et al., Current Biolog. 2019