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In planta Analysis of a cis-Regulatory Cytokinin Response Motif in Arabidopsis and Identification of a Novel Enhancer Sequence

PMG's insight:

11 type-B response regulators (type-B ARRs), and some of them were shown to bind in vitro to the core cytokinin response motif (CRM) 5′-(A/G)GAT(T/C)-3′ or, in case of ARR1, to an extended motif (ECRM), 5′-AAGAT(T/C)TT-3′. Here we obtained in planta proof for the functionality of the latter motif. Promoter deletion analysis of the primary cytokinin response gene ARR6 showed that a combination of two extended motifs within the promoter is required for mediating the full transcriptional activation by ARR1 and other type-B ARRs. CRMs were found to be overrepresented in the vicinity of ECRMs in the promoters of cytokinin-regulated genes suggesting their functional relevance. Moreover, an evolutionary conserved 27 bp-long region between -220 and -193 bp was identified and shown to be required for the full activation by type-B ARRs and the response to cytokinin. This novel enhancer is not bound by the DNA binding domain of ARR1, indicating that additional proteins might be involved in mediating the transcriptional cytokinin response. Furthermore, genome-wide expression profiling identified genes, among them ARR16, whose induction by cytokinin depends on both ARR1 and specific other type-B ARRs. This together with the ECRM/CRM sequence clustering indicates cooperative action of different type-B ARRs for the activation of particular target genes.

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The ATP-Binding Cassette Transporter ABCB19 Regulat... [PLoS One. 2013] - PubMed - NCBI

PubMed comprises more than 22 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
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http://www.ncbi.nlm.nih.gov/pubmed/23560110

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A Role for MORE AXILLARY GROWTH1 (MAX1) in Evolutionary Diversity in Strigolactone Signaling Upstream of MAX2

A Role for MORE AXILLARY GROWTH1 (MAX1) in Evolutionary Diversity in Strigolactone Signaling Upstream of MAX2 | plant developments | Scoop.it
PMG's insight:

a phylogenetic analysis of the MAX/D genes to clarify the relationships of each gene with its wider family and to allow the correlation of events in the evolution of the genes with the evolution of SL function. Our analysis suggests that the notion of a distinct SL pathway is inappropriate. Instead, there may be a diversity of SL-like compounds, the response to which requires a D14/D14-like protein. This ancestral system could have been refined toward distinct ligand-specific pathways channeled through MAX2, the most downstream known component of SL signaling. MAX2 is tightly conserved among land plants and is more diverged from its nearest sister clade than any other SL-related gene, suggesting a pivotal role in the evolution of SL signaling. By contrast, the evidence suggests much greater flexibility upstream of MAX2. The MAX1 gene is a particularly strong candidate for contributing to diversification of inputs upstream of MAX2. Our functional analysis of the MAX1 family demonstrates the early origin of its catalytic function and both redundancy and functional diversification associated with its duplication in angiosperm lineages.

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PlantCell: PIF3 Associates with the Histone Deacetylase HDA15 in .. Etiolated Arabidopsis Seedlings

PlantCell: PIF3 Associates with the Histone Deacetylase HDA15 in .. Etiolated Arabidopsis Seedlings | plant developments | Scoop.it

"PHYTOCHROME INTERACTING FACTOR3 (PIF3) is a key basic helix-loop-helix transcription factor of Arabidopsis thaliana that negatively regulates light responses, repressing chlorophyll biosynthesis, photosynthesis, and photomorphogenesis in the dark. However, the mechanism for the PIF3-mediated transcription regulation remains largely unknown. In this study, we found that the REDUCED POTASSIUM DEPENDENCY3/HISTONE DEACETYLASE1-type histone deacetylase HDA15 directly interacted with PIF3 in vivo and in vitro."


Via Mary Williams
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Mary Williams's curator insight, April 3, 2013 6:43 AM

A while ago, one of the world's top plant scientists tipped me off to the emerging recognition of the role of the PIF family of transcription factors in coordinating growth with environmental inputs. Here's a good review from 2011 on the role of PIFs as "Pivotal components in a cellular signaling hub" (http://www.cell.com/trends/plant-science/retrieve/pii/S1360138510001627).

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Landes Bioscience Journals: Plant Signaling & Behavior

Landes Bioscience Journals: Plant Signaling & Behavior | plant developments | Scoop.it
Cytokinin and auxin antagonistically affect cell proliferation and differentiation and thus regulate root meristem size by influencing the abundance of SHORT HYPOCOTYL2 (SHY2/IAA3).
PMG's insight:

DA1-related protein 2 (DAR2) acts downstream of cytokinin and SHY2 but upstream of PLT1/2 to affect root meristem size.

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The ASYMMETRIC LEAVES complex maintains repression of KNOX homeobox genes via direct recruitment of Polycomb-repressive complex2

A biweekly scientific journal publishing high-quality research in molecular biology and genetics, cancer biology, biochemistry, and related fields
PMG's insight:

Arabidopsis ASYMMETRIC LEAVES complex physically interacts with PRC2 and recruits this complex to the homeobox genes BREVIPEDICELLUS and KNAT2 to stably silence these stem cell regulators in differentiating leaves. The recruitment mechanism resembles the Polycomb response element-based recruitment of PRC2 originally defined in flies and provides the first such example in plants. Combined with recent studies in mammals, our findings reveal a conserved paradigm to epigenetically regulate homeobox gene expression during development.

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The ASYMMETRIC LEAVES complex maintains repression of KNOX homeobox genes via direct recruitment of Polycomb-repressive complex2

A biweekly scientific journal publishing high-quality research in molecular biology and genetics, cancer biology, biochemistry, and related fields
PMG's insight:

Polycomb-repressive complexes (PRCs) ensure the correct spatiotemporal expression of numerous key developmental regulators. Despite their pivotal role, how PRCs are recruited to specific targets remains largely unsolved, particularly in plants. Here we show that the Arabidopsis ASYMMETRIC LEAVES complex physically interacts with PRC2 and recruits this complex to the homeobox genes BREVIPEDICELLUS and KNAT2 to stably silence these stem cell regulators in differentiating leaves. The recruitment mechanism resembles the Polycomb response element-based recruitment of PRC2 originally defined in flies and provides the first such example in plants. Combined with recent studies in mammals, our findings reveal a conserved paradigm to epigenetically regulate homeobox gene expression during development.

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Identification of SHRUBBY, a SHORT-ROOT and SCARECROW interacting protein that controls root growth and radial patterning

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17 SHR-interacting proteins. Among those isolated was At5g24740, which we named SHRUBBY (SHBY). SHBY is a vacuolar sorting protein with similarity to the gene responsible for Cohen syndrome in humans. Hypomorphic alleles of shby caused poor root growth, decreased meristematic activity and defects in radial patterning that are characterized by an increase in the number of cell divisions in the ground tissue that lead to extra cells in the cortex and endodermis, as well as additional cell layers. Analysis of genetic and molecular markers indicates that SHBY acts in a pathway that partially overlaps with SHR, SCR, PLETHORA1 and PLETHORA2 (PLT1 and PLT2). The shby-1 root phenotype was partially phenocopied by treatment of wild-type roots with the proteosome inhibitor MG132 or the gibberellic acid (GA) synthesis inhibitor paclobutrazol (PAC). Our results indicate that SHBY controls root growth downstream of GA in part through the regulation of SHR and SCR.

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Developmental Cell - Regulation of Leaf Maturation by Chromatin-Mediated Modulation of Cytokinin Responses

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Plant shoots display indeterminate growth, while their evolutionary decedents, the leaves, are determinate. Determinate leaf growth is conditioned by the CIN-TCP transcription factors, which promote leaf maturation and are negatively regulated by miR319 in leaf primordia. Here we show that CIN-TCPs reduce leaf sensitivity to cytokinin (CK), a phytohormone implicated in inhibition of differentiation in the shoot. We identify the SWI/SNF chromatin remodeling ATPase BRAHMA (BRM) as a genetic mediator of CIN-TCP activities and CK responses. An interactome screen further revealed that SWI/SNF complex components including BRM preferentially interacted with basic-helix-loop-helix (bHLH) transcription factors and the bHLH-related CIN-TCPs. Indeed, TCP4 and BRM interacted in planta. Both TCP4 and BRM bound the promoter of an inhibitor of CK responses, ARR16, and induced its expression. Reconstituting ARR16 levels in leaves with reduced CIN-TCP activity restored normal growth. Thus, CIN-TCP and BRM together promote determinate leaf growth by stage-specific modification of CK responses.

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Two WUSCHEL-related homeobox Genes, narrow leaf2 and narrow leaf3, Control Leaf Width in Rice

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narrow-leaf phenotype of FL90, a linkage tester line of rice (Oryza sativa). Microscopic and scanning electron micrograph analyses of FL90 leaves revealed defects in the development of marginal regions and a reduction in the number of longitudinal veins. The narrow-leaf phenotype of FL90 shows a two-factor recessive inheritance and is caused by the loss of function of two WUSCHEL-related homeobox genes, NAL2 and NAL3 (NAL2/3), which are duplicate genes orthologous to maize NS1 and NS2 and to Arabidopsis PRS. The overexpression of NAL2/3 in transgenic rice plants results in wider leaves containing increased numbers of veins, suggesting that NAL2/3 expression regulates leaf width. Thus, NAL2/3 can be used to modulate leaf shape and improve agronomic yield in crop plants.

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Auxin signal transcription factor regulates expression of the brassinosteroid receptor gene in rice - Sakamoto - 2013 - The Plant Journal - Wiley Online Library

Auxin signal transcription factor regulates expression of the brassinosteroid receptor gene in rice - Sakamoto - 2013 - The Plant Journal - Wiley Online Library | plant developments | Scoop.it
PMG's insight:

Auxin treatment increased expression of the rice brassinosteroid receptor gene OsBRI1. The promoter of OsBRI1 contains an auxin-response element (AuxRE) that is targeted by auxin-response factor (ARF) transcription factors. An AuxRE mutation abolished the induction of OsBRI1 expression by auxins, and OsBRI1 expression was down-regulated in an arf mutant. The AuxRE motif in the OsBRI1 promoter, and thus the transient up-regulation of OsBRI1 expression caused by treatment with indole-3-acetic acid, is essential for the indole-3-acetic acid-induced increase in sensitivity to brassinosteroids. These findings demonstrate that some ARFs control the degree of brassinosteroid perception required for normal growth and development in rice. Although multi-level interactions between auxins and brassinosteroids have previously been reported, our findings suggest a mechanism by which auxins control cellular sensitivity to brassinosteroids, and further support the notion that interactions between auxins and brassinosteroids are extensive

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Rooting plant development - what's new since Dolan et al 1993 published "Cellular organisation of the Arabidopsis thaliana root"? | Plant Biology Teaching Resources (Higher Education)

Rooting plant development - what's new since Dolan et al 1993 published "Cellular organisation of the Arabidopsis thaliana root"? | Plant Biology Teaching Resources (Higher Education) | plant developments | Scoop.it
Here's a nice two page summary of the state-of-the field in 1993, what we've learned, and where we're going. (RT @PlantTeaching: What's new since Dolan et al 1993 published "Cellular organisation of the Arabidopsis thaliana root"?
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BMC Plant Biology | Abstract | Single-cell-based system to monitor carrier driven cellular auxin homeostasis

Abundance and distribution of the plant hormone auxin play important roles in plant development.
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We developed an easy to use transient single-cell-based system to detect carrier activity. We use the relative changes in signaling output of the auxin responsive promoter element DR5 to indirectly visualize auxin carrier activity. The feasibility of the transient approach was demonstrated by pharmacological and genetic interference with auxin signaling and transport. As a proof of concept, we provide visual evidence that the prominent auxin transport proteins PIN-FORMED (PIN)2 and PIN5 regulate cellular auxin homeostasis at the plasma membrane and endoplasmic reticulum (ER), respectively. Our data suggest that PIN2 and PIN5 have different sensitivities to the auxin transport inhibitor 1-naphthylphthalamic acid (NPA). Also the putative PIN-LIKES (PILS) auxin carrier activity at the ER is insensitive to NPA in our system, indicating that NPA blocks intercellular, but not intracell

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ATM-dependent DNA damage response acts as an upstream trigger for compensation in fas1 mutation during Arabidopsis leaf development

ATM-dependent DNA damage response acts as an upstream trigger for compensation in fas1 mutation during Arabidopsis leaf development | plant developments | Scoop.it
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The fugu2 mutants in Arabidopsis thaliana exhibit typical compensation phenotypes. Here we report that the FUGU2 gene encodes FASCIATA1 (FAS1), the p150 subunit of chromatin assembly factor-1 (CAF-1). To uncover how fas1 mutation induces compensation, we performed microarray analyses and found that many genes involved in the DNA damage response are up-regulated in fas1. Our genetic analysis further showed that activation of the DNA damage response and accompanying decrease of cell number in fas1 depend on ATAXIA TELANGIECTASIA MUTATED (ATM) but not on ATM AND RAD3 RELATED (ATR). Kinematic analysis suggested that the delay in the cell cycle leads to a decrease in cell number in fas1 and that loss of ATM partially restores this phenotype. Consistently, both cell size phenotypes and high ploidy phenotypes of fas1 are also suppressed by atm, supporting that ATM-dependent DNA damage response leads to these phenotypes. Altogether, these data suggest that ATM-dependent DNA damage response acts as an upstream trigger in fas1 to delay the cell cycle and promote an entry into the endocycle, resulting in compensated cell expansion.

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Tissue-Specific Expression of SMALL AUXIN UP RNA41 Differentially Regulates Cell Expansion and Root Meristem Patterning in Arabidopsis

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Among the three primary auxin-induced gene families, Auxin/Indole-3-Acetic Acid (Aux/IAA), Gretchen Hagen3 (GH3) and SMALL AUXIN UP RNA (SAUR), the function of SAUR genes remains unclear. Arabidopsis SAUR genes have been phylogenetically classified into three clades. Recent work has suggested that SAUR19 (clade II) and SAUR63 (clade I) promote cell expansion through the modulation of auxin transport. Herein, we present our work on SAUR41, a clade III SAUR gene with a distinctive expression pattern in root meristems. SAUR41 was normally expressed in the quiescent center and cortex/endodermis initials; upon auxin stimulation, the expression was provoked in the endodermal layer. During lateral root development, SAUR41 was expressed in prospective stem cell niches of lateral root primordia and in expanding endodermal cells surrounding the primordia.

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The ETHYLENE RESPONSE FACTOR 6 Acts as Central Regulator of Leaf Growth under Water Limiting Conditions in Arabidopsis thaliana

The ETHYLENE RESPONSE FACTOR 6 Acts as Central Regulator of Leaf Growth under Water Limiting Conditions in Arabidopsis thaliana | plant developments | Scoop.it
PMG's insight:

enhanced ERF6 expression inhibits cell proliferation and leaf growth by a process involving GA and DELLA signaling. Using an ERF6 inducible overexpression line, we demonstrate that the GA-degrading enzyme GA2-OX6 is transcriptionally induced by ERF6 and that consequently DELLA proteins are stabilized. As a result, ERF6 gain-of-function lines are dwarfed and hypersensitive to osmotic stress, while growth of erf5erf6 loss-of-function mutants is less affected by stress. Next to its role in plant growth under stress, ERF6 also activates the expression of a plethora of osmotic stress-responsive genes, including the well-known stress tolerance genes STZ, MYB51 and WRKY33. Interestingly, the activation of the stress tolerance genes by ERF6 occurs independently from the ERF6-mediated growth inhibition.

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The PP6 Phosphatase Regulates ABI5 Phosphorylation and Abscisic Acid Signaling in Arabidopsis

The PP6 Phosphatase Regulates ABI5 Phosphorylation and Abscisic Acid Signaling in Arabidopsis | plant developments | Scoop.it
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The basic Leucine zipper transcription factor ABSCISIC ACID INSENSITIVE5 (ABI5) is a key regulator of abscisic acid (ABA)–mediated seed germination and postgermination seedling growth. While a family of SUCROSE NONFERMENTING1-related protein kinase2s (SnRK2s) is responsible for ABA-induced phosphorylation and stabilization of ABI5, the phosphatase(s) responsible for dephosphorylating ABI5 is still unknown. Here, we demonstrate that mutations in FyPP1 (for Phytochrome-associated serine/threonine protein phosphatase1) and FyPP3, two homologous genes encoding the catalytic subunits of Ser/Thr PROTEIN PHOSPHATASE6 (PP6), cause an ABA hypersensitive phenotype in Arabidopsis thaliana, including ABA-mediated inhibition of seed germination and seedling growth. Conversely, overexpression of FyPP causes reduced sensitivity to ABA. The ABA hypersensitive phenotype of FyPP loss-of-function mutants is ABI5 dependent, and the amount of phosphorylated and total ABI5 proteins inversely correlates with the levels of FyPP proteins. Moreover, FyPP proteins physically interact with ABI5 in vitro and in vivo, and the strength of the interaction depends on the ABI5 phosphorylation status. In vitro phosphorylation assays show that FyPP proteins directly dephosphorylate ABI5. Furthermore, genetic and biochemical assays show that FyPP proteins act antagonistically with SnRK2 kinases to regulate ABI5 phosphorylation and ABA responses. Thus, Arabidopsis PP6 phosphatase regulates ABA signaling through dephosphorylation and destabilization of ABI5.

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Current Biology - A Dof Transcription Factor, SCAP1, Is Essential for the Development of Functional Stomata in Arabidopsis

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stomatal carpenter 1 (scap1), that develops irregularly shaped guard cells and lacks the ability to control stomatal aperture, including CO2-induced stomatal closing and light-induced stomatal opening. SCAP1 was identified as a plant-specific Dof-type transcription factor expressed in maturing guard cells, but not in guard mother cells. SCAP1 regulates the expression of genes encoding key elements of stomatal functioning and morphogenesis, such as K+ channel protein, MYB60 transcription factor, and pectin methylesterase. Consequently, ion homeostasis was disturbed in scap1 guard cells, and esterification of extracellular pectins was impaired so that the cell walls lining the pores did not mature normally. We conclude that SCAP1 regulates essential processes of stomatal guard cell maturation and functions as a key transcription factor regulating the final stages of guard cell differentiation.

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Cytokinin-dependent specification of the functional megaspore in the Arabidopsis female gametophyte - Cheng - 2013 - The Plant Journal - Wiley Online Library

Cytokinin-dependent specification of the functional megaspore in the Arabidopsis female gametophyte - Cheng - 2013 - The Plant Journal - Wiley Online Library | plant developments | Scoop.it
PMG's insight:

megaspore closest to the chalaza develops into the functional megaspore (FM), and the remaining three megaspores degenerate. Here, we examined the role of cytokinin signaling in FG development. We characterized the FG phenotype in three triple mutants harboring non-overlapping T–DNA insertions in cytokinin AHK receptors. We demonstrate that even the strongest mutant is not a complete null for the cytokinin receptors. Only the strongest mutant displayed a near fully penetrant disruption of FG development, and the weakest triple ahk mutant had only a modest FG phenotype. This suggests that cytokinin signaling is essential for FG development, but that only a low threshold of signaling activity is required for this function. Furthermore, we demonstrate that there is elevated cytokinin signaling localized in the chalaza of the ovule, which is enhanced by the asymmetric localization of cytokinin biosynthetic machinery and receptors. We show that an FM-specific marker is absent in the multiple ahk ovules, suggesting that disruption of cytokinin signaling elements in Arabidopsis blocks the FM specification. Together, this study reveals a chalazal-localized sporophytic cytokinin signal that plays an important role in FM specification in FG development.

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S-nitrosylation of phosphotransfer proteins represses cytokinin signaling

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nitric oxide negatively regulates cytokinin signalling by inhibiting the phosphorelay activity through S-nitrosylation. S-nitrosylation of AHP1 at Cys 115 represses its phosphorylation and subsequent transfer of the phosphoryl group to ARR1. A non-nitrosylatable mutation of AHP1 renders the mutant protein insensitive to nitric oxide in repressing its phosphorylation, and partially relieves the inhibitory effect of nitric oxide on the cytokinin response. Conversely, a nitrosomimetic mutation of AHP1 causes reduced phosphorylation of AHP1 and ARR1, thereby resulting in a compromised cytokinin response. These findings illustrate a mechanism by which redox signalling and cytokinin signalling coordinate plant growth and development.

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The Arabidopsis CDK inhibitor ICK3/KRP5 is rate limiting for primary root growth and promotes growth through cell elongation and endoreduplication

The Arabidopsis CDK inhibitor ICK3/KRP5 is rate limiting for primary root growth and promotes growth through cell elongation and endoreduplication | plant developments | Scoop.it
PMG's insight:

the roles of all ICK/KRP genes in root growth. Analysis of ick/krp null-mutants revealed that only ick3/krp5 was affected in primary root growth. ICK3/KRP5 is strongly expressed in the root apical meristem (RAM), with lower expression in the expansion zone. ick3/krp5 roots grow more slowly than wildtype controls, and this results not from reduction of division in the proliferative region of the RAM but rather reduced expansion as cells exit the meristem. This leads to shorter final cell lengths in different tissues of the ick3/krp5 mutant root, particularly the epidermal non-hair cells, and this reduction in cell size correlates with reduced endoreduplication. Loss of ICK3/KRP5 also leads to delayed germination and in the mature embryo ICK3/KRP5 is specifically expressed in the transition zone between root and hypocotyl. Cells in the transition zone were smaller in the ick3/krp5 mutant, despite the absence of endoreduplication in the embryo suggesting a direct effect of ICK3/KRP5 on cell growth. It is concluded that ICK3/KRP5 is a positive regulator of both cell growth and endoreduplication.

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Developmental Cell - A bHLH Complex Controls Embryonic Vascular Tissue Establishment and Indeterminate Growth in Arabidopsis

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Plants have a remarkable potential for sustained (indeterminate) postembryonic growth. Following their specification in the early embryo, tissue-specific precursor cells first establish tissues and later maintain them postembryonically. The mechanisms underlying these processes are largely unknown. Here we define local control of oriented, periclinal cell division as the mechanism underlying both the establishment and maintenance of vascular tissue. We identify an auxin-regulated basic helix-loop-helix (bHLH) transcription factor dimer as a critical regulator of vascular development. Due to a loss of periclinal divisions, vascular tissue gradually disappears in bHLH-deficient mutants; conversely, ectopic expression is sufficient for triggering periclinal divisions. We show that this dimer operates independently of tissue identity but is restricted to a small vascular domain by integrating overlapping transcription patterns of the interacting bHLH proteins. Our work reveals a common mechanism for tissue establishment and indeterminate vascular development and provides a conceptual framework for developmental control of local cell divisions.

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ScienceDirect.com - Plant Science - SLL1, which encodes a member of the stearoyl-acyl carrier protein fatty acid desaturase family, is involved in cell elongation in lateral roots via regulation of...

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SHORT LATERAL ROOT LENGTH1 (SLL1), which is important for the elongation of lateral roots in rice. An sll1 mutant has decreased lateral root growth due to a defect in the cell elongation. The SLL1 gene encodes a member of the stearoyl-acyl carrier protein fatty acid desaturase family that is the key regulator of overall fatty acid desaturation in plants. We measured the fatty acid content and found that the 18:0 content in the sll1 mutant root was approximately 4 times that in the wild-type root. When the sll1 mutant was grown at 33 °C, it complemented the mutant phenotype to a moderate level, which reflects the importance of the low 18:0 content in maintaining the cell membrane structure. The SLL1 gene was expressed at the lateral root tip, whereas SLL1 expression was not detected in the elongation zone of the crown roots. These results indicate that the lateral root specific defect in sll1 mutant is caused by the different expression patterns of SLL1 in lateral and crown roots. In addition, SLL1 over-expressers produced significantly longer lateral roots compared to the wild-type, and thus SLL1 gene would be very useful for improving rice root architecture.

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PLOS ONE: AHP6 Inhibits Cytokinin Signaling to Regulate the Orientation of Pericycle Cell Division during Lateral Root Initiation

PLOS ONE: AHP6 Inhibits Cytokinin Signaling to Regulate the Orientation of Pericycle Cell Division during Lateral Root Initiation | plant developments | Scoop.it
PLOS ONE: an inclusive, peer-reviewed, open-access resource from the PUBLIC LIBRARY OF SCIENCE. Reports of well-performed scientific studies from all disciplines freely available to the whole world.
PMG's insight:

In Arabidopsis thaliana, lateral roots (LRs) initiate from anticlinal cell divisions of pericycle founder cells. The formation of LR primordia is regulated antagonistically by the phytohormones cytokinin and auxin. It has previously been shown that cytokinin has an inhibitory effect on the patterning events occurring during LR formation. However, the molecular players involved in cytokinin repression are still unknown. In a similar manner to protoxylem formation in Arabidopsis roots, in which AHP6 (ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6) acts as a cytokinin inhibitor, we reveal that AHP6 also functions as a cytokinin repressor during early stages of LR development. We show that AHP6 is expressed at different developmental stages during LR formation and is required for the correct orientation of cell divisions at the onset of LR development. Moreover, we demonstrate that AHP6 influences the localization of the auxin efflux carrier PIN1, which is necessary for patterning the LR primordia. In summary, we show that the inhibition of cytokinin signaling through AHP6 is required to establish the correct pattern during LR initiation.

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ScienceDirect.com - Current Biology - Moderation of Arabidopsis Root Stemness by CLAVATA1 and ARABIDOPSIS CRINKLY4 Receptor Kinase Complexes

ScienceDirect.com - Current Biology - Moderation of Arabidopsis Root Stemness by CLAVATA1 and ARABIDOPSIS CRINKLY4 Receptor Kinase Complexes | plant developments | Scoop.it

Via Andres Zurita, Mary Williams
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Andres Zurita's comment, February 12, 2013 7:24 AM
excellent! thanks for scooping it¡
Mary Williams's comment, February 12, 2013 7:40 AM
My pleasure - the integration of signals at the root meristem is one of my favorite topics!
Andres Zurita's comment, February 12, 2013 7:54 AM
Great, my favorite is root development modulation by abiotic stress