Organ positions and pattern formation in the shoot apex

Callos, Joseph D.; Medford, June I.

doi:10.1046/j.1365-313x.1994.6010001.x

Cited by 55 publications

(32 citation statements)

References 33 publications

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“…The architecture of orthostichy is based on the phyllotaxy of the plant. For example, Arabidopsis has a 3/5-spiral leaf phyllotaxy, which means that every fifth leaf is vertically aligned after three spirals around the plant and leaves in an orthostichy are arranged approximately on a vertical line [9]. The pathway of systemic signalling in response to various stresses, such as wounding, herbivory, or pathogen attack, follows this pattern along orthostichies [1], as evidenced by the demonstration that the translocation of systemic signal molecules, such as salicylic acid, essentially moves with assimilate movement along an orthostichy [10].…”

Section: Introductionmentioning

confidence: 99%

Phloem sap intricacy and interplay with aphid feeding

Dinant

Bonnemain

Girousse

et al. 2010

Comptes Rendus. Biologies

151

118

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ARTICLE INFO ABSTRACT Keywords:Stylectomy Phloem exudation Phloem sap Sieve element EPG Transporters Plant defenceAphididae feed upon the plant sieve elements (SE), where they ingest sugars, nitrogen compounds and other nutrients. For ingestion, aphid stylets penetrate SE, and because of the high hydrostatic pressure in SE, phloem sap exudes out into the stylets. Severing stylets to sample phloem exudates (i.e. stylectomy) has been used extensively for the study of phloem contents. Alternative sampling techniques are spontaneous exudation upon wounding that only works in a few plant species, and the popular EDTA-facilitated exudation technique. These approaches have allowed fundamental advances on the understanding of phloem sap composition and sieve tube physiology, which are surveyed in this review. A more complete picture of metabolites, ions, proteins and RNAs present in phloem sap is now available, which has provided large evidence for the phloem role as a signalling network in addition to its primary role in partitioning of photo-assimilates. Thus, phloem sap sampling methods can have remarkable applications to analyse plant nutrition, physiology and defence responses. Since aphid behaviour is suspected to be affected by phloem sap quality, attempts to manipulate phloem sap content were recently undertaken based on deregulation in mutant plants of genes controlling amino acid or sugar content of phloem sap. This opens up new strategies to control aphid settlement on a plant host. importantes pour l'analyse de la composition de la séve et la physiologie des tubes criblés. Un tableau assez complet des metabolites, des ions, des hormones, des protéines et des ARN presents dans la séve du phloéme est désormais disponible. Ces avancées ont largement étayé le role du phloéme comme réseau de signalisation, en plus de son role central dans la repartition des photo-assimilats. Ces méthodes d'echantillonnage de la séve élaborée ont aussi des applications potentielles remarquables pour l'analyse de la nutrition, la physiologie et les reactions de defense des plantes. Plusieurs études ayant suggéré que la qualité de la séve phloémienne pouvait affecter le comportement alimentaire des pucerons, des tentatives de manipulation de la composition de la séve phloémienne ont été engagées, basées sur la deregulation des genes controlant la teneur en acides amines ou en sucres de la séve, dans les plantes transgéniques. De telles approches ouvrent des strategies nouvelles pour limiter le développement des pucerons sur leur plante hote et ainsi leur nuisibilité. RESUME

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Section: Introductionmentioning

confidence: 99%

Phloem sap intricacy and interplay with aphid feeding

Dinant

Bonnemain

Girousse

et al. 2010

Comptes Rendus. Biologies

151

118

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“…Most of the information on the control of phyllotaxis stems not from genetic analyses but from surgical and pharmacological experiments conducted between 20 and 60 years ago (reviewed in Steeves and Sussex, 1989;Lyndon, 1990Lyndon, , 1998Callos and Medford, 1994). These experiments provided evidence that factors of either a chemical or a physical nature could affect leaf position and the angle between leaves.…”

Section: Introductionmentioning

confidence: 99%

“…In many mutants, disorganized phyllotaxis is part of a pleiotropic phenotype, and the effects on phyllotaxis may well be indirect. Only in the recently described maize abphyl1 mutant has a specific phyllotactic alteration, from distichous (alternate) to decussate (opposite), been observed (Jackson and Hake, 1999).Most of the information on the control of phyllotaxis stems not from genetic analyses but from surgical and pharmacological experiments conducted between 20 and 60 years ago (reviewed in Steeves and Sussex, 1989;Lyndon, 1990Lyndon, , 1998Callos and Medford, 1994). These experiments provided evidence that factors of either a chemical or a physical nature could affect leaf position and the angle between leaves.…”

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Auxin Regulates the Initiation and Radial Position of Plant Lateral Organs

2000

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Leaves originate from the shoot apical meristem, a small mound of undifferentiated tissue at the tip of the stem. Leaf formation begins with the selection of a group of founder cells in the so-called peripheral zone at the flank of the meristem, followed by the initiation of local growth and finally morphogenesis of the resulting bulge into a differentiated leaf. Whereas the mechanisms controlling the switch between meristem propagation and leaf initiation are being identified by genetic and molecular analyses, the radial positioning of leaves, known as phyllotaxis, remains poorly understood. Hormones, especially auxin and gibberellin, are known to influence phyllotaxis, but their specific role in the determination of organ position is not clear. We show that inhibition of polar auxin transport blocks leaf formation at the vegetative tomato meristem, resulting in pinlike naked stems with an intact meristem at the tip. Microapplication of the natural auxin indole-3-acetic acid (IAA) to the apex of such pins restores leaf formation. Similarly, exogenous IAA induces flower formation on Arabidopsis pin-formed1-1 inflorescence apices, which are blocked in flower formation because of a mutation in a putative auxin transport protein. Our results show that auxin is required for and sufficient to induce organogenesis both in the vegetative tomato meristem and in the Arabidopsis inflorescence meristem. In this study, organogenesis always strictly coincided with the site of IAA application in the radial dimension, whereas in the apical-basal dimension, organ formation always occurred at a fixed distance from the summit of the meristem. We propose that auxin determines the radial position and the size of lateral organs but not the apical-basal position or the identity of the induced structures. INTRODUCTIONLeaf primordia develop in regular patterns from the shoot apical meristem. In the majority of flowering plants, the leaves are arranged in spirals, with the divergence angle between successive leaves approaching the Fibonacci angle of 137.5 Њ , the so-called golden ratio (Steeves and Sussex, 1989;Lyndon, 1990Lyndon, , 1998Jean, 1994). Molecular and genetic analyses have recently identified various genes that regulate meristem development and leaf formation. Some of these genes encode transcription factors of the homeobox class (Vollbrecht et al., 1991;Long et al., 1996;Kerstetter et al., 1997; Taylor, 1997;Mayer et al., 1998), whereas others, such as clavata1 , clavata3, and zwille, appear to be involved in cell-to-cell signaling Moussian et al., 1998;Fletcher et al., 1999; Trotochaud et al., 1999). Current models postulate that these genes control the balance between meristem self-propagation and the production of organogenic tissue.Whereas genetic analyses provide us with an ever more detailed description of meristem maintenance and propagation, the molecular nature of the mechanisms that trigger leaf initiation and ensure that leaves form at the proper angles relative to each other remains to be established. In many m...

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“…For instance, floral organs arise in concentric whorls from the floral meristem as bulges of cells separated by boundary regions with a low rate of cellular proliferation (Furner, 1996). Proliferating leaf primordia are separated from the shoot meristem by slower proliferating boundary regions (Callos and Medford, 1994), and trichomes arise through highly increased proliferation of individual leaf epidermal cells compared with the surrounding cells (Hulskamp et al, 1994). Several genes have been identified that are expressed specifically in organ or meristem boundaries.…”

Section: Introductionmentioning

confidence: 99%

The CUP-SHAPED COTYLEDON3 Gene Is Required for Boundary and Shoot Meristem Formation in Arabidopsis

et al. 2003

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From an enhancer trap screen for genes expressed in Arabidopsis embryos, we identified a gene expressed from the octant stage onward in the boundary between the two presumptive cotyledons and in a variety of postembryonic organ and meristem boundaries. This gene, CUP-SHAPED COTYLEDON3 ( CUC3 ), encodes a putative NAC-domain transcription factor that is homologous with CUC1 and CUC2. Analysis of a CUC3 hypomorph and a putative cuc3 null mutant indicates that CUC3 function is partially redundant with that of CUC1 and CUC2 in the establishment of the cotyledon boundary and the shoot meristem, thus revealing an even higher degree of redundancy in this class of genes than was thought previously. The CUC3 expression pattern, the cuc3 phenotypes, and CUC3 expression in a series of shoot meristem mutants and transgenes suggest a primary role for CUC 3 in the establishment of boundaries that contain cells with low proliferation and/or differentiation rates. The CUC -mediated establishment of such boundaries may be essential for the initiation of shoot meristems.

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Organ positions and pattern formation in the shoot apex

Cited by 55 publications

References 33 publications

Phloem sap intricacy and interplay with aphid feeding

Phloem sap intricacy and interplay with aphid feeding

Auxin Regulates the Initiation and Radial Position of Plant Lateral Organs

The CUP-SHAPED COTYLEDON3 Gene Is Required for Boundary and Shoot Meristem Formation in Arabidopsis

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