Regulation of phyllotaxis

Reinhardt, Didier

doi:10.1387/ijdb.041922dr

Cited by 61 publications

(59 citation statements)

References 51 publications

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“…Aerial organs, such as leaves and flowers, are arranged regularly around the plant stem following characteristic phyllotactic patterns (Fig. 4A,B) (Reinhardt, 2005). Again, several mutants affected in auxin synthesis, transport or perception show defects in phyllotaxis, pointing to a role for auxin in organ formation and regular arrangement (Bennett et al, 1995, Gälweiler et al, 1998, Okada et al, 1991.…”

Section: Establishment Of Repetitive Patterns In Morphogenesis: Auxinmentioning

confidence: 93%

Instructive roles for hormones in plant development

Alabadı́

Blázquez

Carbonell³

et al. 2009

Int. J. Dev. Biol.

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Plants, like animals, construct their body following modular sets of instructions that determine cell fate, morphogenesis and patterning, among other building requirements. Hormones regulate plant growth in different ways, and there is increasing evidence for a decisive function of certain hormones in the establishment of developmental programs, equivalent to the role of peptidic molecules and signals of another nature in animal embryo development. Here, we review this role of hormones as instructive agents, and illustrate it with examples such as the generation of morphogenetic gradients by auxin (which determine organ patterning and phyllotaxis), the specification of cell fate at the shoot meristem by gibberellins and cytokinins, the switch between alternative developmental programs (photo-and skotomorphogenesis) by gibberellins and brassinosteroids, and the decision between pistil senescence or fruit growth after anthesis. KEY WORDS: gibberellin, auxin, cytokinin, patterning, differentiation Hormones in plant developmentSince the discovery of the first few plant hormones, these compounds have been attributed numerous roles regulating the physiology, growth responses caused by stress and development of plants. However, they do not always act as their metazoan counterparts, for which the term "hormone" was coined. One of the basic differences is that, unlike in animals, plant hormones are not synthesized in a particular and specialized organ and then transported to the target organs. Rather, the ability to synthesize hormones is general to all plant tissues, and very often hormones act in the same cells where they are produced (Bishopp et al., 2006). Plant hormones are also referred to with the generic name of plant growth regulators, to stress the fact that their function as a group is not restricted to precise physiological processes. For instance, auxins have been shown to increase cell division rate; gibberellins and brassinosteroids promote cell expansion; abscisic acid induces the physiological state of dormancy; and ethylene is required for the maturation of fleshy fruits. Nevertheless, there is increasing evidence that hormones act in many cases as an "instructive" signal in plant development, and this particular role is surprisingly similar to the action driven by peptide hormones and proteins during animal development, such as Notch and BMP (Ehebauer et al., 2006, Raftery andSutherland, 2003). The key issue is that, in this instructive role, plant hormones do not act as mere transducers or messengers of other higher rank signals, nor do they promote growth in Int. J. Dev. Biol. 53: 1597-1608 (2009) general. Instead, the information provided by these hormones is the basis for deciding between two alternative developmental programs, or establishing domains of identity within a given tissue.In this review, we wish to underscore the role of hormones as instructive signals in plant development, illustrating it with only a few examples: how auxin acts as a bona fide morphogen in establishing s...

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Section: Establishment Of Repetitive Patterns In Morphogenesis: Auxinmentioning

confidence: 93%

Instructive roles for hormones in plant development

Alabadı́

Blázquez

Carbonell³

et al. 2009

Int. J. Dev. Biol.

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“…In wild-type plants, organs are initiated successively on the flanks of the SAM with a spiral arrangement. This pattern, referred to as phyllotaxy, depends on predictive auxin gradients in the meristem (Reinhardt, 2005). However, previous studies indicated that the majority of pny mutants have a wild-type meristem structure.…”

Section: Bp and Pny Restrict Knat6 And Knat2 Expression To Promote Comentioning

confidence: 99%

Interaction ofKNAT6andKNAT2withBREVIPEDICELLUSandPENNYWISEinArabidopsisInflorescences

et al. 2008

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The three amino acid loop extension (TALE) homeodomain superfamily, which comprises the KNOTTED-like and BEL1-like families, plays a critical role in regulating meristem activity. We previously demonstrated a function for KNAT6 (for KNOTTED-like from Arabidopsis thaliana 6) in shoot apical meristem and boundary maintenance during embryogenesis. KNAT2, the gene most closely related to KNAT6, does not play such a role. To investigate the contribution of KNAT6 and KNAT2 to inflorescence development, we examined their interactions with two TALE genes that regulate internode patterning, BREVIPEDICELLUS (BP) and PENNYWISE (PNY). Our data revealed distinct and overlapping interactions of KNAT6 and KNAT2 during inflorescence development. Removal of KNAT6 activity suppressed the pny phenotype and partially rescued the bp phenotype. Removal of KNAT2 activity had an effect only in the absence of both BP and KNAT6 or in the absence of both BP and PNY. Consistent with this, KNAT6 and KNAT2 expression patterns were enlarged in both bp and pny mutants. Thus, the defects seen in pny and bp are attributable mainly to the misexpression of KNAT6 and to a lesser extent of KNAT2. Hence, our data showed that BP and PNY restrict KNAT6 and KNAT2 expression to promote correct inflorescence development. This interaction was also revealed in the carpel.

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“…One common pattern is spiral phyllotaxis, in which organs are produced in a spiral around the shoot axis separated by approximately 137.5 degrees, the golden angle derived from the ratio of consecutive numbers in the Fibonacci sequence. During phyllotactic patterning, PIN protein localisation in cells of the epidermis of the SAM apparently directs local sites of auxin accumulation and these sites correspond to the position at which the organ primordia develop (9,(26)(27)(28) . This process requires the continuous repositioning of PIN proteins to create the sequence of sites of auxin accumulation needed to trigger the initiation of successive organs.…”

Section: Auxin's Roles In Plant Developmentmentioning

confidence: 99%

Computer simulation: The imaginary friend of auxin transport biology

et al. 2010

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Regulated transport of the plant hormone auxin is central to many aspects of plant development. Directional transport, mediated by membrane transporters, produces patterns of auxin distribution in tissues that trigger developmental processes, such as vascular patterning or leaf formation. Experimentation has produced a lot of largely qualitative data providing strong evidence for multiple feedback systems between auxin and its transport. However the exact mechanisms concerned remain elusive and the experiments required to evaluate alternative hypotheses are challenging. Because of this, computational modelling now plays an important role in auxin transport research. Here we review current approaches and underlying assumptions of computational auxin transport models, including recent attempts to unify conflicting mechanistic explanations. In addition we discuss in general how computer simulation of these processes is proving to be an increasingly effective method of hypothesis generation and testing, and how simulation can be used to direct future experiments.

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Regulation of phyllotaxis

Cited by 61 publications

References 51 publications

Instructive roles for hormones in plant development

Instructive roles for hormones in plant development

Interaction ofKNAT6andKNAT2withBREVIPEDICELLUSandPENNYWISEinArabidopsisInflorescences

Computer simulation: The imaginary friend of auxin transport biology

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