Vascular cambium produces xylem (wood) and phloem, and together with the cork cambium, which produces a protective layer at the surface called phellem (cork), they provide thickness to plant organs. Our group is studying the development of cambium by using Arabidopsis thaliana root as a model. We combine lineage tracing and microscopy with molecular genetics to understand growth dynamics of the stem cells of the vascular cambium at a cellular resolution. By using these techniques, we recently showed that cells with a xylem identity direct adjacent vascular cambial cells to divide and function as stem cells (Smetana et al 2019). Therefore, we propose that xylem-identity cells constitute an organizer. Molecular studies revealed that the organizer is defined by local maximum of plant hormone auxin and subsequent expression of a set of cambial transcription factors. Further lineage tracing experiments revealed that xylem and phloem originate from a single, bifacial stem cell in each radial cell file, thus confirming a classical theory of a uniseriate vascular cambium (Sanio 1873). As a follow up, we have studied whether other cambial regulators interact with the factors defining the organizer. The latest discoveries of these studies will be presented during the seminar.
High levels of auxin signalling define the stem-cell organizer of the vascular cambium
Smetana O, Mäkilä R, Lyu M, Amiryousefi A, Sánchez Rodríguez F, Wu MF, Solé-Gil A, Leal Gavarrón M, Siligato R, Miyashima S, Roszak P, Blomster T, Reed JW, Broholm S, Mähönen AP. Nature. 2019 565:485-489
MultiSite Gateway-Compatible Cell Type-Specific Gene-Inducible System for Plants.
Siligato R, Wang X, Yadav SR, Lehesranta S, Ma G, Ursache R, Sevilem I, Zhang J, Gorte M, Prasad K, Wrzaczek M, Heidstra R, Murphy A, Scheres B, Mähönen AP. Plant Physiol. 2016 170:627-41.
Parsimonious Model of Vascular Patterning Links Transverse Hormone Fluxes to Lateral Root Initiation: Auxin Leads the Way, while Cytokinin Levels Out.
el-Showk S, Help-Rinta-Rahko H, Blomster T, Siligato R, Marée AF, Mähönen AP, Grieneisen VA. PLoS Comput Biol. 2015 11:e1004450
PLETHORA gradient formation mechanism separates auxin responses.
Mähönen, A.P., ten Tusscher, K., Siligato, R., Smetana, O., Díaz-Triviño, S., Salojärvi, J., Wachsman, G., Prasad, K., Heidstra, R. & Scheres B. Nature. 2014 515:125-129