AINTEGUMENTA-LIKE proteins: hubs in a plethora of networks
Horstman, A. ; Willemsen, V. ; Boutilier, K.A. ; Heidstra, R. - \ 2014
Trends in Plant Science 19 (2014)3. - ISSN 1360-1385 - p. 146 - 157.
stem-cell niche - ethylene-responsive element - lateral root initiation - homeodomain finger proteins - actin-depolymerizing factor - homeotic gene apetala2 - shoot apical meristem - dna-binding proteins - transcription factors - arabidopsis root
Members of the AINTEGUMENTA-LIKE (AIL) family of APETALA 2/ETHYLENE RESPONSE FACTOR (AP2/ERF) domain transcription factors are expressed in all dividing tissues in the plant, where they have central roles in developmental processes such as embryogenesis, stem cell niche specification, meristem maintenance, organ positioning, and growth. When overexpressed, AIL proteins induce adventitious growth, including somatic embryogenesis and ectopic organ formation. The Arabidopsis (Arabidopsis thaliana) genome contains eight AIL genes, including AINTEGUMENTA, BABY BOOM, and the PLETHORA genes. Studies on these transcription factors have revealed their intricate relationship with auxin as well as their involvement in an increasing number of gene regulatory networks, in which extensive crosstalk and feedback loops have a major role.
Rooting plant development
Scheres, B. - \ 2013
Development 140 (2013)5. - ISSN 0950-1991 - p. 939 - 941.
arabidopsis root - cell fate - meristem - differentiation - mechanism - shoot - framework - epidermis - division - pattern
In 1993, we published a paper in Development detailing the anatomical structure of the Arabidopsis root. The paper described how root growth was maintained by the precisely tuned activity of a small set of 'initials', which acted as the source of dividing and differentiating cells, and how these stem cell-like cells surrounded a few infrequently dividing cells. This work underpinned subsequent research on root developmental biology and sparked a detailed molecular analysis of how stem cell groups are positioned and maintained in plants.
Spatial coordination between stem cell activity and cell differentiation in the root meristem
Moubayidin, L. ; Mambro, R. Di; Sozzani, R. ; Pacifici, E. ; Salvi, E. ; Terpstra, I. ; Bao, D. ; Dijken, A. van; Dello loio, R. ; Perilli, S. ; Ljung, K. ; Benfey, P.N. ; Heidstra, R. ; Costantino, P. ; Sabatini, S. - \ 2013
Developmental Cell 26 (2013)4. - ISSN 1534-5807 - p. 405 - 415.
gras gene family - arabidopsis root - auxin biosynthesis - scarecrow - expression - thaliana - transport - division - growth - niche
A critical issue in development is the coordination of the activity of stem cell niches with differentiation of their progeny to ensure coherent organ growth. In the plant root, these processes take place at opposite ends of the meristem and must be coordinated with each other at a distance. Here, we show that in Arabidopsis, the gene SCR presides over this spatial coordination. In the organizing center of the root stem cell niche, SCR directly represses the expression of the cytokinin-response transcription factor ARR1, which promotes cell differentiation, controlling auxin production via the ASB1 gene and sustaining stem cell activity. This allows SCR to regulate, via auxin, the level of ARR1 expression in the transition zone where the stem cell progeny leaves the meristem, thus controlling the rate of differentiation. In this way, SCR simultaneously controls stem cell division and differentiation, ensuring coherent root growth.
A mutually inhibitory interaction between auxin and cytokinin specifies vascular pattern in roots.
Bishopp, A. ; Help, H. ; El-Showk, S. ; Weijers, D. ; Scheres, B.J.G. ; Friml, J. ; Benkova, E. ; Pekka Mahonen, A. ; Helariutta, Y. - \ 2011
Current Biology 21 (2011)11. - ISSN 0960-9822 - p. 917 - 926.
cup-shaped-cotyledon - stem-cell niche - class iiihd-zip - arabidopsis root - meristem activity - hormonal-control - gene family - embryo - efflux - embryogenesis
Background Whereas the majority of animals develop toward a predetermined body plan, plants show iterative growth and continually produce new organs and structures from actively dividing meristems. This raises an intriguing question: How are these newly developed organs patterned? In Arabidopsis embryos, radial symmetry is broken by the bisymmetric specification of the cotyledons in the apical domain. Subsequently, this bisymmetry is propagated to the root promeristem. Results Here we present a mutually inhibitory feedback loop between auxin and cytokinin that sets distinct boundaries of hormonal output. Cytokinins promote the bisymmetric distribution of the PIN-FORMED (PIN) auxin efflux proteins, which channel auxin toward a central domain. High auxin promotes transcription of the cytokinin signaling inhibitor AHP6, which closes the interaction loop. This bisymmetric auxin response domain specifies the differentiation of protoxylem in a bisymmetric pattern. In embryonic roots, cytokinin is required to translate a bisymmetric auxin response in the cotyledons to a bisymmetric vascular pattern in the root promeristem. Conclusions Our results present an interactive feedback loop between hormonal signaling and transport by which small biases in hormonal input are propagated into distinct signaling domains to specify the vascular pattern in the root meristem. It is an intriguing possibility that such a mechanism could transform radial patterns and allow continuous vascular connections between other newly emerging organs.
Cellulose microfibril deposition: coordinated activity at the plant plasma membrane
Lindeboom, J.J. ; Mulder, B. ; Vos, J.W. ; Ketelaar, M.J. ; Emons, A.M.C. - \ 2008
Journal of Microscopy 231 (2008)2. - ISSN 0022-2720 - p. 192 - 200.
cortical microtubule arrays - cell-wall - root hairs - equisetum-hyemale - arabidopsis root - calcofluor white - cytochalasin-d - pollen tubes - in-vitro - synthase
Plant cell wall production is a membrane-bound process. Cell walls are composed of cellulose microfibrils, embedded inside a matrix of other polysaccharides and glycoproteins. The cell wall matrix is extruded into the existing cell wall by exocytosis. This same process also inserts the cellulose synthase complexes into the plasma membrane. These complexes, the nanomachines that produce the cellulose microfibrils, move inside the plasma membrane leaving the cellulose microfibrils in their wake. Cellulose microfibril angle is an important determinant of cell development and of tissue properties and as such relevant for the industrial use of plant material. Here, we provide an integrated view of the events taking place in the not more than 100 nm deep area in and around the plasma membrane, correlating recent results provided by the distinct field of plant cell biology. We discuss the coordinated activities of exocytosis, endocytosis, and movement of cellulose synthase complexes while producing cellulose microfibrils and the link of these processes to the cortical microtubules