The shoot apical meristem and development of vascular architectureThis review is one of a selection of papers published on the Special Theme of Shoot Apical Meristems.

The shoot apical meristem (SAM) functions to generate external architecture and internal tissue pattern as well as to maintain a self-perpetuating population of stem-cell-like cells. The internal three-dimensional architecture of the vascular system corresponds closely to the external arrangement of lateral organs, or phyllotaxis. This paper reviews this correspondence for dicotyledonous plants in general and in Arabidopsis thaliana (L.) Heynh., specifically. Analysis is partly based on the expression patterns of the class III homeodomain-leucine zipper transcription factor ARABIDOPSIS THALIANA HOMEOBOX GENE 8 (ATHB8), a marker of the procambial and preprocambial stages of vascular development, and on the anatomical criteria for recognizing vascular tissue pattern. The close correspondence between phyllotaxis and vascular pattern present in mature tissues arises at early stages of development, at least by the first plastochron of leaf primordium outgrowth. Current literature provides an integrative model in which local variation in auxin concentration regulates both primordium formation on the SAM and the first indications of a procambial prepattern in the position of primordium leaf trace as well as in the elaboration of leaf vein pattern. The prospects for extending this model to the development of the complex three-dimensional vascular architecture of the shoot are promising.

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Toward a 3D model of phyllotaxis based on a biochemically plausible auxin-transport mechanism

10.1101/398628 ◽

2018 ◽

Author(s):

Félix P. Hartmann ◽

Pierre Barbier de Reuille ◽

Cris Kuhlemeier

Keyword(s):

Shoot Apical Meristem ◽

Apical Meristem ◽

Auxin Transport ◽

Vascular System ◽

Three Dimensional ◽

Integrative Approach ◽

Dimensional Model ◽

Three Dimensional Model ◽

Leaf Formation ◽

Cell Layers

AbstractPolar auxin transport lies at the core of many self-organizing phenomena sustaining continuous plant organogenesis. In angiosperms, the shoot apical meristem is a potentially unique system in which the two main modes of auxin-driven patterning— convergence and canalization—co-occur in a coordinated manner and in a fully three-dimensional geometry. In the epidermal layer, convergence points form, from which auxin is canalized towards inner tissue. Each of these two patterning processes has been extensively investigated separately, but the integration of both in the shoot apical meristem remains poorly understood. We present here a first attempt of a three-dimensional model of auxin-driven patterning during phyllotaxis. We base our simulations on a biochemically plausible mechanism of auxin transport proposed by Cieslak et al. (2015) which generates both convergence and canalization patterns. We are able to reproduce most of the dynamics of PIN1 polarization in the meristem, and we explore how the epidermal and inner cell layers act in concert during phyllotaxis. In addition, we discuss the mechanism by which initiating veins connect to the already existing vascular system.Author summaryThe regularity of leaf arrangement around stems has long puzzled scientists. The key role played by the plant hormone auxin is now well established. On the surface of the tissue responsible for leaf formation, auxin accumulates at several points, from which new leaves eventually emerge. Auxin also guides the progression of new veins from the nascent leaves to the vascular system of the plant. Models of auxin transport have been developed to explain either auxin accumulation or auxin-driven venation. We propose the first three-dimensional model embracing both phenomena using a unifying mechanism of auxin transport. This integrative approach allows an assessment of our present knowledge on how auxin contributes to the early development of leaves. Our model reproduces many observations of auxin dynamics. It highlights how the inner and epidermal tissues act together to position new leaves. We also show that an additional, yet unknown, mechanism is required to attract new developing veins towards the main vasculature of the plant.

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Developmental events and shoot apical meristem gene expression patterns during shoot development in Arabidopsis thaliana

The Plant Journal ◽

10.1046/j.1365-313x.2002.01479.x ◽

2002 ◽

Vol 32 (6) ◽

pp. 867-877 ◽

Cited By ~ 92

Author(s):

Andrew J. Cary ◽

Ping Che ◽

Stephen H. Howell

Keyword(s):

Gene Expression ◽

Arabidopsis Thaliana ◽

Shoot Apical Meristem ◽

Apical Meristem ◽

Expression Patterns ◽

Shoot Development ◽

Gene Expression Patterns

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Ectopic Expression of BraYAB1-702, a Member of YABBY Gene Family in Chinese Cabbage, Causes Leaf Curling, Inhibition of Development of Shoot Apical Meristem and Flowering Stage Delaying in Arabidopsis thaliana

International Journal of Molecular Sciences ◽

10.3390/ijms140714872 ◽

2013 ◽

Vol 14 (7) ◽

pp. 14872-14891 ◽

Cited By ~ 9

Author(s):

Xin-Ling Zhang ◽

Ze-Ping Yang ◽

Jing Zhang ◽

Lu-Gang Zhang

Keyword(s):

Arabidopsis Thaliana ◽

Gene Family ◽

Chinese Cabbage ◽

Shoot Apical Meristem ◽

Apical Meristem ◽

Ectopic Expression ◽

Flowering Stage ◽

Leaf Curling ◽

Yabby Gene

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Nuclear import of the transcription factor SHOOT MERISTEMLESS depends on heterodimerization with BLH proteins expressed in discrete sub-domains of the shoot apical meristem of Arabidopsis thaliana

Nucleic Acids Research ◽

10.1093/nar/gkl016 ◽

2006 ◽

Vol 34 (4) ◽

pp. 1281-1292 ◽

Cited By ~ 70

Author(s):

M. Cole

Keyword(s):

Arabidopsis Thaliana ◽

Transcription Factor ◽

Nuclear Import ◽

Shoot Apical Meristem ◽

Apical Meristem ◽

Shoot Meristemless

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Characterisation of three shoot apical meristem mutants of Arabidopsis thaliana

Development ◽

10.1242/dev.116.2.397 ◽

1992 ◽

Vol 116 (2) ◽

pp. 397-403 ◽

Cited By ~ 19

Author(s):

H. M. Ottoline Leyser ◽

I. J. Furner

Keyword(s):

Arabidopsis Thaliana ◽

Root Growth ◽

Shoot Apical Meristem ◽

Apical Meristem ◽

Floral Development ◽

Wild Type ◽

Recessive Mutations ◽

Phenotypic Characterisation ◽

Dicotyledonous Plants ◽

And Function

The shoot apical meristem of dicotyledonous plants is highly regulated both structurally and functionally, but little is known about the mechanisms involved in this regulation. Here we describe the genetic and phenotypic characterisation of recessive mutations at three loci of Arabidopsis thaliana in which meristem structure and function are disrupted. The loci are Clavata1 (Clv1), Fasciata1 (Fas1) and Fasciata2 (Fas2). Plants mutant at these loci are fasciated having broad, flat stems and disrupted phyllotaxy. In all cases, the fasciations are associated with shoot apical meristem enlargement and altered floral development. While all the mutants share some phenotypic features they can be divided into two classes. The pleiotropic fas1 and fas2 mutants are unable to initiate wild- type organs, show major alterations in meristem structure and have reduced root growth. In contrast, clv1 mutant plants show near wild-type organ phenotypes, more subtle changes in shoot apical meristem structure and wild-type root growth.

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Ontogenetic Changes in Auxin Biosynthesis and Distribution Determine the Organogenic Activity of the Shoot Apical Meristem in pin1 Mutants

International Journal of Molecular Sciences ◽

10.3390/ijms20010180 ◽

2019 ◽

Vol 20 (1) ◽

pp. 180 ◽

Cited By ~ 3

Author(s):

Alicja Banasiak ◽

Magdalena Biedroń ◽

Alicja Dolzblasz ◽

Mateusz Adam Berezowski

Keyword(s):

Shoot Apical Meristem ◽

Apical Meristem ◽

Auxin Transport ◽

Vascular System ◽

Auxin Biosynthesis ◽

Wild Type ◽

Ontogenetic Changes ◽

Auxin Distribution ◽

Stem Development ◽

Knockout Mutation

In the shoot apical meristem (SAM) of Arabidopsis, PIN1-dependent polar auxin transport (PAT) regulates two crucial developmental processes: organogenesis and vascular system formation. However, the knockout mutation in the PIN1 gene does not fully inhibit these two processes. Therefore, we investigated a potential source of auxin for organogenesis and vascularization during inflorescence stem development. We analyzed auxin distribution in wild-type (WT) and pin1 mutant plants using a refined protocol of auxin immunolocalization; auxin activity, with the response reporter pDR5:GFP; and expression of auxin biosynthesis genes YUC1 and YUC4. Our results revealed that regardless of the functionality of PIN1-mediated PAT, auxin is present in the SAM and vascular strands. In WT plants, auxin always accumulates in all cells of the SAM, whereas in pin1 mutants, its localization within the SAM changes ontogenetically and is related to changes in the structure of the vascular system, organogenic activity of SAM, and expression levels of YUC1 and YUC4 genes. Our findings indicate that the presence of auxin in the meristem of pin1 mutants is an outcome of at least two PIN1-independent mechanisms: acropetal auxin transport from differentiated tissues with the use of vascular strands and auxin biosynthesis within the SAM.

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