Ari Pekka Mähönen - Cell Fate Decisions in the Arabidopsis Root Cambium
14:00 - 15:30
Ari Pekka Mähönen
Institute of Biotechnology/Department of Biosciences, University of Helsinki, Finnland
Despite the importance of the vascular cambium in plant biology and in wood production, the molecular and cellular mechanisms underlying cambial activity remain largely unknown. Particularly, it is unknown where the cambial stem cells are located, and how the stem cell niche is organized to drive cambial growth.In animal stem cell studies lineage tracing has been the method for locating the stem cells. In this method single cell clones marked with reporter expression are generated within a population of dividing cells. The clones are transmitted to all daughter cells of the initial cell, resulting in a marked sector within the tissue. By analysing the size and distribution of the sectors the position and the mitotic activity of dividing cells and stem cells can be deduced. In order to understand the cell lineage relations in the Arabidopsis root cambium, we generated GUS/GFP sectors by using two step CRE-lox based clonal activation system. To understand which cells in the primary tissue contribute to the cambium formation we induced single cell clones during the primary development of the root and analysed the growing sectors during the secondary development. We also generated marked sectors in active cambium to map the position of stem cells and to understand the growth dynamics of the cambial cells. In my seminar presentation I will explain how we are utilizing the lineage tracing data to provide mechanistic understanding of cambium regulation.
Relevant recent publications:
1. Immanen J, Nieminen K, Smolander OP, Kojima M,
Alonso Serra J, Koskinen P, Zhang J, Elo AK, Mähönen AP, Street N, Bhalerao RP,
Paulin L, Auvinen P, Sakakibara H, Helariutta Y. Cytokinin and auxin display
distinct but interconnected distribution and signaling profiles to stimulate
cambial activity. Curr Biol. 2016 26: 1990-7
2: el-Showk S, Help-Rinta-Rahko H, Blomster T,
Siligato R, Marée AF, Mähönen AP, Grieneisen VA. Parsimonious Model of Vascular
Patterning Links Transverse Hormone Fluxes to Lateral Root Initiation: Auxin
Leads the Way, while Cytokinin Levels Out. PLoS Comput Biol. 2015 11: e1004450
3: Nieminen K, Blomster T, Helariutta Y, Mähönen AP. Vascular
Cambium Development. Arabidopsis Book. 2015 13: e0177.
4: Mähönen AP, ten Tusscher K, Siligato R, Smetana O,
Díaz-Triviño S, Salojärvi J, Wachsman G, Prasad K, Heidstra R, Scheres B.
PLETHORA gradient formation mechanism separates auxin responses. Nature. 2014
5: Bishopp A, Help H, El-Showk S, Weijers D, Scheres
B, Friml J, Benková E, Mähönen AP, Helariutta Y. A mutually inhibitory
interaction between auxin and cytokinin specifies vascular pattern in roots.
Curr Biol. 2011 21:917-26.