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1.
J Exp Bot ; 64(14): 4479-90, 2013 Nov.
Article in English | MEDLINE | ID: mdl-24006420

ABSTRACT

Transcription factors are proposed as suitable targets for the control of traits such as yield or food quality in plants. This study reports the results of a functional genomics research effort that identified ATHB17, a transcription factor from the homeodomain-leucine zipper class II family, as a novel target for the enhancement of photosynthetic capacity. It was shown that ATHB17 is expressed natively in the root quiescent centre (QC) from Arabidopsis embryos and seedlings. Analysis of the functional composition of genes differentially expressed in the QC from a knockout mutant (athb17-1) compared with its wild-type sibling revealed the over-representation of genes involved in auxin stimulus, embryo development, axis polarity specification, and plastid-related processes. While no other phenotypes were observed in athb17-1 plants, overexpression of ATHB17 produced a number of phenotypes in Arabidopsis including enhanced chlorophyll content. Image analysis of isolated mesophyll cells of 35S::ATHB17 lines revealed an increase in the number of chloroplasts per unit cell size, which is probably due to an increase in the number of proplastids per meristematic cell. Leaf physiological measurements provided evidence of improved photosynthetic capacity in 35S::ATHB17 lines on a per unit leaf area basis. Estimates of the capacity for ribulose-1,5-bisphosphate-saturated and -limited photosynthesis were significantly higher in 35S::ATHB17 lines.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/physiology , Chloroplasts/metabolism , Homeodomain Proteins/metabolism , Leucine Zippers , Photosynthesis , Transcription Factors/metabolism , Arabidopsis/genetics , Arabidopsis/growth & development , Arabidopsis/radiation effects , Arabidopsis Proteins/genetics , Chloroplasts/radiation effects , Gene Expression Regulation, Plant/radiation effects , Genes, Plant/genetics , Homeodomain Proteins/genetics , In Situ Hybridization , Light , Mesophyll Cells/cytology , Mesophyll Cells/metabolism , Mesophyll Cells/radiation effects , Mutation/genetics , Phenotype , Photoperiod , Photosynthesis/radiation effects , Plant Roots/metabolism , Plants, Genetically Modified , RNA, Messenger/genetics , RNA, Messenger/metabolism , Transcription Factors/genetics
2.
Plant J ; 70(5): 855-65, 2012 Jun.
Article in English | MEDLINE | ID: mdl-22321262

ABSTRACT

In plants, the ERF/EREBP family of transcriptional regulators plays a key role in adaptation to various biotic and abiotic stresses. These proteins contain a conserved AP2 DNA-binding domain and several uncharacterized motifs. Here, we describe a short motif, termed 'EDLL', that is present in AtERF98/TDR1 and other clade members from the same AP2 sub-family. We show that the EDLL motif, which has a unique arrangement of acidic amino acids and hydrophobic leucines, functions as a strong activation domain. The motif is transferable to other proteins, and is active at both proximal and distal positions of target promoters. As such, the EDLL motif is able to partly overcome the repression conferred by the AtHB2 transcription factor, which contains an ERF-associated amphiphilic repression (EAR) motif. We further examined the activation potential of EDLL by analysis of the regulation of flowering time by NF-Y (nuclear factor Y) proteins. Genetic evidence indicates that NF-Y protein complexes potentiate the action of CONSTANS in regulation of flowering in Arabidopsis; we show that the transcriptional activation function of CONSTANS can be substituted by direct fusion of the EDLL activation motif to NF-YB subunits. The EDLL motif represents a potent plant activation domain that can be used as a tool to confer transcriptional activation potential to heterologous DNA-binding proteins.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/genetics , Gene Expression Regulation, Plant , Transcriptional Activation , Amino Acid Motifs , Amino Acid Sequence , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Cloning, Molecular , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Escherichia coli/genetics , Escherichia coli/metabolism , Flowers/metabolism , Flowers/physiology , Genes, Plant , Genes, Reporter , Molecular Sequence Data , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Plants, Genetically Modified/physiology , Promoter Regions, Genetic , Protein Structure, Tertiary , Protoplasts/cytology , Protoplasts/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Repressor Proteins/genetics , Repressor Proteins/metabolism , Time Factors , Transcription Factors/genetics , Transcription Factors/metabolism , Transfection
3.
Plant Physiol ; 156(4): 2109-23, 2011 Aug.
Article in English | MEDLINE | ID: mdl-21632973

ABSTRACT

A B-box zinc finger protein, B-BOX32 (BBX32), was identified as playing a role in determining hypocotyl length during a large-scale functional genomics study in Arabidopsis (Arabidopsis thaliana). Further analysis revealed that seedlings overexpressing BBX32 display elongated hypocotyls in red, far-red, and blue light, along with reduced cotyledon expansion in red light. Through comparative analysis of mutant and overexpression line phenotypes, including global expression profiling and growth curve studies, we demonstrate that BBX32 acts antagonistically to ELONGATED HYPOCOTYL5 (HY5). We further show that BBX32 interacts with SALT TOLERANCE HOMOLOG2/BBX21, another B-box protein previously shown to interact with HY5. Based on these data, we propose that BBX32 functions downstream of multiple photoreceptors as a modulator of light responses. As such, BBX32 potentially has a native role in mediating gene repression to maintain dark adaptation.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/genetics , Basic-Leucine Zipper Transcription Factors/metabolism , Carrier Proteins/metabolism , Gene Expression Regulation, Plant/radiation effects , Light Signal Transduction/radiation effects , Light , Nuclear Proteins/metabolism , Transcription Factors/metabolism , Arabidopsis/radiation effects , Arabidopsis Proteins/genetics , Carrier Proteins/genetics , Darkness , Gene Expression Profiling , Genes, Plant/genetics , Hypocotyl/growth & development , Hypocotyl/radiation effects , Light Signal Transduction/genetics , Models, Biological , Protein Binding/radiation effects
4.
Proc Natl Acad Sci U S A ; 106(44): 18843-8, 2009 Nov 03.
Article in English | MEDLINE | ID: mdl-19843695

ABSTRACT

Multicellular organs are composed of distinct cell types with unique assemblages of translated mRNAs. Here, ribosome-associated mRNAs were immunopurified from specific cell populations of intact seedlings using Arabidopsis thaliana lines expressing a FLAG-epitope tagged ribosomal protein L18 (FLAG-RPL18) via developmentally regulated promoters. The profiling of mRNAs in ribosome complexes, referred to as the translatome, identified differentially expressed mRNAs in 21 cell populations defined by cell-specific expression of FLAG-RPL18. Phloem companion cells of the root and shoot had the most distinctive translatomes. When seedlings were exposed to a brief period of hypoxia, a pronounced reprioritization of mRNA enrichment in the cell-specific translatomes occurred, including a ubiquitous rise in 49 mRNAs encoding transcription factors, signaling proteins, anaerobic metabolism enzymes, and uncharacterized proteins. Translatome profiling also exposed an intricate molecular signature of transcription factor (TF) family member mRNAs that was markedly reconfigured by hypoxia at global and cell-specific levels. In addition to the demonstration of the complexity and plasticity of cell-specific populations of ribosome-associated mRNAs, this study provides an in silico dataset for recognition of differentially expressed genes at the cell-, region-, and organ-specific levels.


Subject(s)
Arabidopsis/cytology , Arabidopsis/genetics , Gene Expression Profiling , Gene Expression Regulation, Plant , Protein Biosynthesis , Cell Hypoxia , Organ Specificity , Plants, Genetically Modified , Promoter Regions, Genetic/genetics , RNA, Messenger/genetics , RNA, Messenger/isolation & purification , RNA, Messenger/metabolism , Ribosomes/metabolism , Stress, Physiological , Transcription Factors/genetics , Transcription Factors/metabolism
5.
Genetics ; 165(3): 1541-50, 2003 Nov.
Article in English | MEDLINE | ID: mdl-14668401

ABSTRACT

Leaves are one of the most conspicuous and important organs of all seed plants. A fundamental source of morphological diversity in leaves is the degree to which the leaf is dissected by lobes and leaflets. We used publicly available segmental introgression lines to describe the quantitative trait loci (QTL) controlling the difference in leaf dissection seen between two tomato species, Lycopersicon esculentum and L. pennellii. We define eight morphological characteristics that comprise the mature tomato leaf and describe loci that affect each of these characters. We found 30 QTL that contribute one or more of these characters. Of these 30 QTL, 22 primarily affect leaf dissection and 8 primarily affect leaf size. On the basis of which characters are affected, four classes of loci emerge that affect leaf dissection. The majority of the QTL produce phenotypes intermediate to the two parent lines, while 5 QTL result in transgression with drastically increased dissection relative to both parent lines.


Subject(s)
Plant Leaves/metabolism , Quantitative Trait Loci , Solanum lycopersicum/metabolism , Genetic Complementation Test , Solanum lycopersicum/genetics , Phenotype
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