ALTERED MERISTEM PROGRAM1 sustains cellular differentiation by limiting HD-ZIP III transcription factor gene expression.

Plants show remarkable developmental and regenerative plasticity through the sustained activity of stem cells in meristems. Under certain conditions, pluripotency can even be reestablished in cells that have already entered differentiation. Mutation of the putative carboxypeptidase ALTERED MERISTEM PROGRAM1 (AMP1) in Arabidopsis (Arabidopsis thaliana) causes a set of hypertrophic phenotypes, indicating a defect in the suppression of pluripotency.

SlCESTA Is a Brassinosteroid-Regulated bHLH Transcription Factor of Tomato That Promotes Chilling Tolerance and Fruit Growth When Over-Expressed.

Brassinosteroids (BRs) are required for various aspects of plant growth and development, but also participate in stress responses. The hormones convey their activity through transcriptional regulation and posttranslational modification of transcription factors and one class are basic helix-loop-helix (bHLH) proteins of the BR Enhanced Expression (BEE) subfamily, which in include BEE1-3 and CESTA (CES). CES and the BEEs promote the expression of different BR-responsive genes, including genes encoding gibberellin (GA) biosynthetic and catabolizing enzymes, as well as cold-responsive genes.

Species-Specific Variation in Abscisic Acid Homeostasis and Responses Impacts Important Traits in Orphan Crops.

and are plant species native to Africa, but grow in most tropical and subtropical regions of the world. They are rich in vitamins, minerals, and essential oils and are traditional leafy vegetables and medicinal plants in Sub-Saharan Africa. The plants are still mainly collected from the wild but shall be taken into cultivation and an important aim in the domestication of these species is to improve traits that are relevant for crop production.

A novel chemical inhibitor of polar auxin transport promotes shoot regeneration by local enhancement of HD-ZIP III transcription.

De novo shoot organogenesis is a prerequisite for numerous applications in plant research and breeding but is often a limiting factor, for example, in genome editing approaches. Class III homeodomain-leucine zipper (HD-ZIP III) transcription factors have been characterized as crucial regulators of shoot specification, however up-stream components controlling their activity during shoot regeneration are only partially identified. In a chemical genetic screen, we isolated ZIC2, a novel activator of HD-ZIP III activity.

Transcription factor BES1 interacts with HSFA1 to promote heat stress resistance of plants.

Heat stress is a major environmental stress type that can limit plant growth and development. To survive sudden temperature increases, plants utilize the heat shock response, an ancient signaling pathway. Initial results had suggested a role for brassinosteroids (BRs) in this response.

AMP1 and CYP78A5/7 act through a common pathway to govern cell fate maintenance in Arabidopsis thaliana.

Higher plants can continuously form new organs by the sustained activity of pluripotent stem cells. These stem cells are embedded in meristems, where they produce descendants, which undergo cell proliferation and differentiation programs in a spatiotemporally-controlled manner. Under certain conditions, pluripotency can be reestablished in descending cells and this reversion in cell fate appears to be actively suppressed by the existing stem cell pool.

ALTERED MERISTEM PROGRAM1 Restricts Shoot Meristem Proliferation and Regeneration by Limiting HD-ZIP III-Mediated Expression of RAP2.6L.

Plants show an indeterminate mode of growth by the activity of organ forming stem cell niches in apically positioned meristems. The correct formation and activity of these meristems are a prerequisite for their adaptive development and also allow the maintenance of organogenesis under adverse circumstances such as wounding. Mutation of the putative Arabidopsis () Glu carboxypeptidase ALTERED MERISTEM PROGRAM1 (AMP1) results in Arabidopsis plants with enlarged shoot apical meristems, supernumerary stem cell pools, and higher leaf formation rate.

The Small Molecule Hyperphyllin Enhances Leaf Formation Rate and Mimics Shoot Meristem Integrity Defects Associated with AMP1 Deficiency.

ALTERED MERISTEM PROGRAM1 (AMP1) is a member of the M28 family of carboxypeptidases with a pivotal role in plant development and stress adaptation. Its most prominent mutant defect is a unique hypertrophic shoot phenotype combining a strongly increased organ formation rate with enhanced meristem size and the formation of ectopic meristem poles. However, so far the role of AMP1 in shoot development could not be assigned to a specific molecular pathway nor is its biochemical function resolved.

Brassinosteroids Are Master Regulators of Gibberellin Biosynthesis in Arabidopsis.

Plant growth and development are highly regulated processes that are coordinated by hormones including the brassinosteroids (BRs), a group of steroids with structural similarity to steroid hormones of mammals. Although it is well understood how BRs are produced and how their signals are transduced, BR targets, which directly confer the hormone's growth-promoting effects, have remained largely elusive. Here, we show that BRs regulate the biosynthesis of gibberellins (GAs), another class of growth-promoting hormones, in Arabidopsis thaliana.

ALTERED MERISTEM PROGRAM1 suppresses ectopic stem cell niche formation in the shoot apical meristem in a largely cytokinin-independent manner.

Plants are able to reiteratively form new organs in an environmentally adaptive manner during postembryonic development. Organ formation in plants is dependent on stem cell niches (SCNs), which are located in the so-called meristems. Meristems show a functional zonation along the apical-basal axis and the radial axis.

Interplay between phosphorylation and SUMOylation events determines CESTA protein fate in brassinosteroid signalling.

Brassinosteroids (BRs) are steroid hormones that are essential for plant growth. Responses to these hormones are mediated by transcription factors of the bri1-EMS suppressor 1/brassinazole resistant 1 subfamily, and BRs activate these factors by impairing their inhibitory phosphorylation by GSK3/shaggy-like kinases. Here we show that BRs induce nuclear compartmentalization of CESTA (CES), a basic helix-loop-helix transcription factor that regulates BR responses, and reveal that this process is regulated by CES SUMOylation.

Bikinin-like inhibitors targeting GSK3/Shaggy-like kinases: characterisation of novel compounds and elucidation of their catabolism in planta.

Background: Plant GSK-3/Shaggy-like kinases are key players in brassinosteroid (BR) signalling which impact on plant development and participate in response to wounding, pathogens and salt stress. Bikinin was previously identified in a chemical genetics screen as an inhibitor targeting these kinases. To dissect the structural elements crucial for inhibition of GSK-3/Shaggy-like kinases by bikinin and to isolate more potent compounds we synthesised a number of related substances and tested their inhibitory activity in vitro and in vivo using Arabidopsis thaliana.

Strigolactone signaling is required for auxin-dependent stimulation of secondary growth in plants.

Long distance cell-to-cell communication is critical for the development of multicellular organisms. In this respect, plants are especially demanding as they constantly integrate environmental inputs to adjust growth processes to different conditions. One example is thickening of shoots and roots, also designated as secondary growth.

CESTA, a positive regulator of brassinosteroid biosynthesis.

Brassinosteroids (BRs) are steroid hormones that are essential for the development of plants. A tight control of BR homeostasis is vital for modulating their impact on growth responses. Although it is recognized that the rapid adaptation of de novo synthesis has a key role in adjusting required BR levels, our knowledge of the mechanisms governing feedback control is limited.

Strigolactones enhance competition between shoot branches by dampening auxin transport.

Strigolactones (SLs), or their derivatives, were recently demonstrated to act as endogenous shoot branching inhibitors, but their biosynthesis and mechanism of action are poorly understood. Here we show that the branching phenotype of mutants in the Arabidopsis P450 family member, MAX1, can be fully rescued by strigolactone addition, suggesting that MAX1 acts in SL synthesis. We demonstrate that SLs modulate polar auxin transport to control branching and that both the synthetic SL GR24 and endogenous SL synthesis significantly reduce the basipetal transport of a second branch-regulating hormone, auxin.

Putative Arabidopsis transcriptional adaptor protein (PROPORZ1) is required to modulate histone acetylation in response to auxin.

Plant development is highly adaptable and controlled by a combination of various regulatory circuits that integrate internal and environmental cues. The phytohormone auxin mediates such growth responses, acting as a dynamic signal in the control of morphogenesis via coordinating the interplay between cell cycle progression and cell differentiation. Mutants in the chromatin-remodeling component PROPORZ1 (PRZ1; also known as AtADA2b) are impaired in auxin effects on morphogenesis, suggestive of an involvement of PRZ1-dependent control of chromatin architecture in the determination of hormone responses.

The Arabidopsis MAX pathway controls shoot branching by regulating auxin transport.

Background: Plants achieve remarkable plasticity in shoot system architecture by regulating the activity of secondary shoot meristems, laid down in the axil of each leaf. Axillary meristem activity, and hence shoot branching, is regulated by a network of interacting hormonal signals that move through the plant. Among these, auxin, moving down the plant in the main stem, indirectly inhibits axillary bud outgrowth, and an as yet undefined hormone, the synthesis of which in Arabidopsis requires MAX1, MAX3, and MAX4, moves up the plant and also inhibits shoot branching.

Intracellular trafficking and proteolysis of the Arabidopsis auxin-efflux facilitator PIN2 are involved in root gravitropism.

Root gravitropism describes the orientation of root growth along the gravity vector and is mediated by differential cell elongation in the root meristem. This response requires the coordinated, asymmetric distribution of the phytohormone auxin within the root meristem, and depends on the concerted activities of PIN proteins and AUX1 - members of the auxin transport pathway. Here, we show that intracellular trafficking and proteasome activity combine to control PIN2 degradation during root gravitropism.

MAX1 encodes a cytochrome P450 family member that acts downstream of MAX3/4 to produce a carotenoid-derived branch-inhibiting hormone.

The plant shoot body plan is highly variable, depending on the degree of branching. Characterization of the max1-max4 mutants of Arabidopsis demonstrates that branching is regulated by at least one carotenoid-derived hormone. Here we show that all four MAX genes act in a single pathway, with MAX1, MAX3, and MAX4 acting in hormone synthesis, and MAX2 acting in perception.

Detoxification of the Fusarium mycotoxin deoxynivalenol by a UDP-glucosyltransferase from Arabidopsis thaliana.

Plant pathogenic fungi of the genus Fusarium cause agriculturally important diseases of small grain cereals and maize. Trichothecenes are a class of mycotoxins produced by different Fusarium species that inhibit eukaryotic protein biosynthesis and presumably interfere with the expression of genes induced during the defense response of the plants. One of its members, deoxynivalenol, most likely acts as a virulence factor during fungal pathogenesis and frequently accumulates in grain to levels posing a threat to human and animal health.

PROPORZ1, a putative Arabidopsis transcriptional adaptor protein, mediates auxin and cytokinin signals in the control of cell proliferation.

Plants generate cells and organs throughout their life cycle. Plant cell proliferation relates to the activity of dividing meristematic cells, which subsequently differentiate in a position- and lineage-dependent manner. The events underlying the regulation of cell division and further differentiation processes are under tight control of both intrinsic and environmental parameters.