In response to environmental changes, plants continuously make architectural changes in order to optimize their growth and development. The regulation of plant branching, influenced by environmental conditions and affecting hormone balance and gene expression, is crucial for agronomic purposes due to its direct correlation with yield. Strigolactones (SL), the youngest class of phytohormones, function to shape the architecture of plants by inhibiting axillary outgrowth. Barley plants harboring the mutation in the HvDWARF14 (HvD14) gene, which encodes the SL-specific receptor, produce almost twice as many tillers as wild-type (WT) Sebastian plants. Here, through hormone profiling and comparison of transcriptomic and proteomic changes between 2- and 4-week-old plants of WT and hvd14 genotypes, we elucidate a regulatory mechanism that might affect the tillering of SL-insensitive plants. The analysis showed statistically significant increased cytokinin content and decreased auxin and abscisic acid content in 'bushy' hvd14 compared to WT, which aligns with the commonly known actions of these hormones regarding branching regulation. Further, transcriptomic and proteomic analysis revealed a set of differentially expressed genes (DEG) and abundant proteins (DAP), among which 11.6% and 14.6% were associated with phytohormone-related processes, respectively. Bioinformatics analyses then identified a series of potential SL-dependent transcription factors (TF), which may control the differences observed in the hvd14 transcriptome and proteome. Comparison to available Arabidopsis thaliana data implicates a sub-selection of these TF as being involved in the transduction of SL signal in both monocotyledonous and dicotyledonous plants.

• Keywords
• Hordeum vulgare, Branching, Phytohormone cross-talk, Strigolactones,
• MeSH
• Cytokinins metabolism   MeSH
• Heterocyclic Compounds, 3-Ring * MeSH
• Homeostasis MeSH
• Hordeum * growth & development   metabolism   MeSH
• Lactones * metabolism   MeSH
• Mutation MeSH
• Proteome analysis   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Growth Regulators * metabolism   MeSH
• Plant Proteins genetics   metabolism   MeSH
• Gene Expression Profiling MeSH
• Transcription Factors metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Cytokinins MeSH
• GR24 strigolactone MeSH Browser
• Heterocyclic Compounds, 3-Ring * MeSH
• Lactones * MeSH
• Proteome MeSH
• Plant Growth Regulators * MeSH
• Plant Proteins MeSH
• Transcription Factors MeSH

Spontaneously arising channels that transport the phytohormone auxin provide positional cues for self-organizing aspects of plant development such as flexible vasculature regeneration or its patterning during leaf venation. The auxin canalization hypothesis proposes a feedback between auxin signaling and transport as the underlying mechanism, but molecular players await discovery. We identified part of the machinery that routes auxin transport. The auxin-regulated receptor CAMEL (Canalization-related Auxin-regulated Malectin-type RLK) together with CANAR (Canalization-related Receptor-like kinase) interact with and phosphorylate PIN auxin transporters. camel and canar mutants are impaired in PIN1 subcellular trafficking and auxin-mediated PIN polarization, which macroscopically manifests as defects in leaf venation and vasculature regeneration after wounding. The CAMEL-CANAR receptor complex is part of the auxin feedback that coordinates polarization of individual cells during auxin canalization.

• MeSH
• Arabidopsis enzymology   genetics   MeSH
• Biological Transport MeSH
• Indoleacetic Acids metabolism   MeSH
• Protein Interaction Mapping MeSH
• Membrane Transport Proteins metabolism   MeSH
• Protein Kinases genetics   metabolism   MeSH
• Arabidopsis Proteins metabolism   MeSH
• Transcription Factors metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Membrane Transport Proteins MeSH
• PIN1 protein, Arabidopsis MeSH Browser
• Protein Kinases MeSH
• Arabidopsis Proteins MeSH
• Transcription Factors MeSH
• WRKY23 protein, Arabidopsis MeSH Browser

Directional transport of the phytohormone auxin is a versatile, plant-specific mechanism regulating many aspects of plant development. The recently identified plant hormones, strigolactones (SLs), are implicated in many plant traits; among others, they modify the phenotypic output of PIN-FORMED (PIN) auxin transporters for fine-tuning of growth and developmental responses. Here, we show in pea and Arabidopsis that SLs target processes dependent on the canalization of auxin flow, which involves auxin feedback on PIN subcellular distribution. D14 receptor- and MAX2 F-box-mediated SL signaling inhibits the formation of auxin-conducting channels after wounding or from artificial auxin sources, during vasculature de novo formation and regeneration. At the cellular level, SLs interfere with auxin effects on PIN polar targeting, constitutive PIN trafficking as well as clathrin-mediated endocytosis. Our results identify a non-transcriptional mechanism of SL action, uncoupling auxin feedback on PIN polarity and trafficking, thereby regulating vascular tissue formation and regeneration.

• MeSH
• Arabidopsis genetics   metabolism   MeSH
• Heterocyclic Compounds, 3-Ring metabolism   MeSH
• Pisum sativum genetics   metabolism   MeSH
• Indoleacetic Acids metabolism   MeSH
• Lactones metabolism   MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Gene Expression Regulation, Plant genetics   physiology   MeSH
• Plant Growth Regulators metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• GR24 strigolactone MeSH Browser
• Heterocyclic Compounds, 3-Ring MeSH
• Indoleacetic Acids MeSH
• Lactones MeSH
• Arabidopsis Proteins MeSH
• Plant Growth Regulators MeSH

Plant survival depends on vascular tissues, which originate in a self-organizing manner as strands of cells co-directionally transporting the plant hormone auxin. The latter phenomenon (also known as auxin canalization) is classically hypothesized to be regulated by auxin itself via the effect of this hormone on the polarity of its own intercellular transport. Correlative observations supported this concept, but molecular insights remain limited. In the current study, we established an experimental system based on the model Arabidopsis thaliana, which exhibits auxin transport channels and formation of vasculature strands in response to local auxin application. Our methodology permits the genetic analysis of auxin canalization under controllable experimental conditions. By utilizing this opportunity, we confirmed the dependence of auxin canalization on a PIN-dependent auxin transport and nuclear, TIR1/AFB-mediated auxin signaling. We also show that leaf venation and auxin-mediated PIN repolarization in the root require TIR1/AFB signaling. Further studies based on this experimental system are likely to yield better understanding of the mechanisms underlying auxin transport polarization in other developmental contexts.

• Keywords
• Arabidopsis thaliana, PIN1, TIR1/AFB, auxin, auxin canalization, cell polarity,
• MeSH
• Arabidopsis * genetics   metabolism   MeSH
• F-Box Proteins * genetics   MeSH
• Indoleacetic Acids MeSH
• Arabidopsis Proteins * genetics   metabolism   MeSH
• Receptors, Cell Surface genetics   metabolism   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Growth Regulators MeSH
• Signal Transduction MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• F-Box Proteins * MeSH
• Indoleacetic Acids MeSH
• Arabidopsis Proteins * MeSH
• Receptors, Cell Surface MeSH
• Plant Growth Regulators MeSH
• TIR1 protein, Arabidopsis MeSH Browser

Auxin is unique among plant hormones due to its directional transport that is mediated by the polarly distributed PIN auxin transporters at the plasma membrane. The canalization hypothesis proposes that the auxin feedback on its polar flow is a crucial, plant-specific mechanism mediating multiple self-organizing developmental processes. Here, we used the auxin effect on the PIN polar localization in Arabidopsis thaliana roots as a proxy for the auxin feedback on the PIN polarity during canalization. We performed microarray experiments to find regulators of this process that act downstream of auxin. We identified genes that were transcriptionally regulated by auxin in an AXR3/IAA17- and ARF7/ARF19-dependent manner. Besides the known components of the PIN polarity, such as PID and PIP5K kinases, a number of potential new regulators were detected, among which the WRKY23 transcription factor, which was characterized in more detail. Gain- and loss-of-function mutants confirmed a role for WRKY23 in mediating the auxin effect on the PIN polarity. Accordingly, processes requiring auxin-mediated PIN polarity rearrangements, such as vascular tissue development during leaf venation, showed a higher WRKY23 expression and required the WRKY23 activity. Our results provide initial insights into the auxin transcriptional network acting upstream of PIN polarization and, potentially, canalization-mediated plant development.

• MeSH
• Arabidopsis genetics   growth & development   MeSH
• Plants, Genetically Modified MeSH
• Gene Regulatory Networks * drug effects   MeSH
• Plant Roots drug effects   genetics   growth & development   metabolism   MeSH
• Indoleacetic Acids metabolism   pharmacology   MeSH
• Membrane Transport Proteins genetics   metabolism   MeSH
• Microarray Analysis MeSH
• Cell Polarity * genetics   MeSH
• Arabidopsis Proteins genetics   metabolism   physiology   MeSH
• Gene Expression Regulation, Plant drug effects   MeSH
• Gene Expression Profiling MeSH
• Transcription Factors physiology   MeSH
• Feedback, Physiological drug effects   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Membrane Transport Proteins MeSH
• PIN1 protein, Arabidopsis MeSH Browser
• Arabidopsis Proteins MeSH
• Transcription Factors MeSH
• WRKY23 protein, Arabidopsis MeSH Browser

Apical dominance is one of the fundamental developmental phenomena in plant biology, which determines the overall architecture of aerial plant parts. Here we show apex decapitation activated competition for dominance in adjacent upper and lower axillary buds. A two-nodal-bud pea (Pisum sativum L.) was used as a model system to monitor and assess auxin flow, auxin transport channels, and dormancy and initiation status of axillary buds. Auxin flow was manipulated by lateral stem wounds or chemically by auxin efflux inhibitors 2,3,5-triiodobenzoic acid (TIBA), 1-N-naphtylphtalamic acid (NPA), or protein synthesis inhibitor cycloheximide (CHX) treatments, which served to interfere with axillary bud competition. Redirecting auxin flow to different points influenced which bud formed the outgrowing and dominant shoot. The obtained results proved that competition between upper and lower axillary buds as secondary auxin sources is based on the same auxin canalization principle that operates between the shoot apex and axillary bud.

• MeSH
• Biological Transport MeSH
• Pisum sativum drug effects   genetics   growth & development   MeSH
• Indoleacetic Acids pharmacology   MeSH
• Gene Expression Regulation, Plant drug effects   MeSH
• Plant Growth Regulators pharmacology   MeSH
• Plant Proteins genetics   MeSH
• Plant Stems drug effects   genetics   growth & development   MeSH
• Plant Shoots drug effects   genetics   growth & development   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Plant Growth Regulators MeSH
• Plant Proteins MeSH

Synchronized tissue polarization during regeneration or de novo vascular tissue formation is a plant-specific example of intercellular communication and coordinated development. According to the canalization hypothesis, the plant hormone auxin serves as polarizing signal that mediates directional channel formation underlying the spatio-temporal vasculature patterning. A necessary part of canalization is a positive feedback between auxin signaling and polarity of the intercellular auxin flow. The cellular and molecular mechanisms of this process are still poorly understood, not the least, because of a lack of a suitable model system. We show that the main genetic model plant, Arabidopsis (Arabidopsis thaliana) can be used to study the canalization during vascular cambium regeneration and new vasculature formation. We monitored localized auxin responses, directional auxin-transport channels formation, and establishment of new vascular cambium polarity during regenerative processes after stem wounding. The increased auxin response above and around the wound preceded the formation of PIN1 auxin transporter-marked channels from the primarily homogenous tissue and the transient, gradual changes in PIN1 localization preceded the polarity of newly formed vascular tissue. Thus, Arabidopsis is a useful model for studies of coordinated tissue polarization and vasculature formation after wounding allowing for genetic and mechanistic dissection of the canalization hypothesis.

• MeSH
• Arabidopsis physiology   MeSH
• Cambium physiology   MeSH
• Indoleacetic Acids metabolism   MeSH
• Regeneration MeSH
• Plant Stems physiology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH

Bud outgrowth is controlled by environmental and endogenous factors. Through the use of the photosynthesis inhibitor norflurazon and of masking experiments, evidence is given here that light acts mainly as a morphogenic signal in the triggering of bud outgrowth and that initial steps in the light signaling pathway involve cytokinins (CKs). Indeed, in rose (Rosa hybrida), inhibition of bud outgrowth by darkness is suppressed solely by the application of CKs. In contrast, application of sugars has a limited effect. Exposure of plants to white light (WL) induces a rapid (after 3-6 h of WL exposure) up-regulation of CK synthesis (RhIPT3 and RhIPT5), of CK activation (RhLOG8), and of CK putative transporter RhPUP5 genes and to the repression of the CK degradation RhCKX1 gene in the node. This leads to the accumulation of CKs in the node within 6 h and in the bud at 24 h and to the triggering of bud outgrowth. Molecular analysis of genes involved in major mechanisms of bud outgrowth (strigolactone signaling [RwMAX2], metabolism and transport of auxin [RhPIN1, RhYUC1, and RhTAR1], regulation of sugar sink strength [RhVI, RhSUSY, RhSUC2, and RhSWEET10], and cell division and expansion [RhEXP and RhPCNA]) reveal that, when supplied in darkness, CKs up-regulate their expression as rapidly and as intensely as WL Additionally, up-regulation of CKs by WL promotes xylem flux toward the bud, as evidenced by Methylene Blue accumulation in the bud after CK treatment in the dark. Altogether, these results suggest that CKs are initial components of the light signaling pathway that controls the initiation of bud outgrowth.

• MeSH
• Models, Biological MeSH
• Time Factors MeSH
• Cytokinins metabolism   pharmacology   MeSH
• Meristem genetics   growth & development   metabolism   MeSH
• Reverse Transcriptase Polymerase Chain Reaction MeSH
• Gene Expression Regulation, Plant drug effects   radiation effects   MeSH
• Plant Growth Regulators metabolism   pharmacology   MeSH
• Rosa genetics   growth & development   metabolism   MeSH
• Plant Proteins genetics   metabolism   MeSH
• Signal Transduction drug effects   genetics   radiation effects   MeSH
• Light * MeSH
• Darkness MeSH
• Plant Shoots genetics   growth & development   metabolism   MeSH
• Gene Expression Regulation, Developmental drug effects   radiation effects   MeSH
• Xylem genetics   growth & development   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cytokinins MeSH
• Plant Growth Regulators MeSH
• Plant Proteins MeSH