The Pentatricopeptide Repeat Protein EMB2654 Is Essential for Trans-Splicing of a Chloroplast Small Ribosomal Subunit Transcript.

We report the partial complementation and subsequent comparative molecular analysis of two nonviable mutants impaired in chloroplast translation, one (emb2394) lacking the RPL6 protein, and the other (emb2654) carrying a mutation in a gene encoding a P-class pentatricopeptide repeat protein. We show that EMB2654 is required for the trans-splicing of the plastid rps12 transcript and that therefore the emb2654 mutant lacks Rps12 protein and fails to assemble the small subunit of the plastid ribosome, explaining the loss of plastid translation and consequent embryo-lethal phenotype. Predictions of the EMB2654 binding site match a small RNA "footprint" located on the 5' half of the trans-spliced intron that is almost absent in the partially complemented mutant.

Knockout of the two evolutionarily conserved peroxisomal 3-ketoacyl-CoA thiolases in Arabidopsis recapitulates the abnormal inflorescence meristem 1 phenotype.

A specific function for peroxisomal β-oxidation in inflorescence development in Arabidopsis thaliana is suggested by the mutation of the abnormal inflorescence meristem 1 gene, which encodes one of two peroxisomal multifunctional proteins. Therefore, it should be possible to identify other β-oxidation mutants that recapitulate the aim1 phenotype. Three genes encode peroxisomal 3-ketoacyl-CoA thiolase (KAT) in Arabidopsis.

Identification of new adventitious rooting mutants amongst suppressors of the Arabidopsis thaliana superroot2 mutation.

The plant hormone auxin plays a central role in adventitious rooting and is routinely used with many economically important, vegetatively propagated plant species to promote adventitious root initiation and development on cuttings. Nevertheless the molecular mechanisms through which it acts are only starting to emerge. The Arabidopsis superroot2-1 (sur2-1) mutant overproduces auxin and, as a consequence, develops excessive adventitious roots in the hypocotyl.

Peroxisomal ATP-binding cassette transporter COMATOSE and the multifunctional protein abnormal INFLORESCENCE MERISTEM are required for the production of benzoylated metabolites in Arabidopsis seeds.

Secondary metabolites derived from benzoic acid (BA) are of central importance in the interactions of plants with pests, pathogens, and symbionts and are potentially important in plant development. Peroxisomal β-oxidation has recently been shown to contribute to BA biosynthesis in plants, but not all of the enzymes involved have been defined. In this report, we demonstrate that the peroxisomal ATP-binding cassette transporter COMATOSE is required for the accumulation of benzoylated secondary metabolites in Arabidopsis (Arabidopsis thaliana) seeds, including benzoylated glucosinolates and substituted hydroxybenzoylcholines.

Leaves of the Arabidopsis maltose exporter1 mutant exhibit a metabolic profile with features of cold acclimation in the warm.

Background: Arabidopsis plants accumulate maltose from starch breakdown during cold acclimation. The Arabidopsis mutant, maltose excess1-1, accumulates large amounts of maltose in the plastid even in the warm, due to a deficient plastid envelope maltose transporter. We therefore investigated whether the elevated maltose level in mex1-1 in the warm could result in changes in metabolism and physiology typical of WT plants grown in the cold.

An ecological genetic delineation of local seed-source provenance for ecological restoration.

An increasingly important practical application of the analysis of spatial genetic structure within plant species is to help define the extent of local provenance seed collection zones that minimize negative impacts in ecological restoration programs. Here, we derive seed sourcing guidelines from a novel range-wide assessment of spatial genetic structure of 24 populations of Banksia menziesii (Proteaceae), a widely distributed Western Australian tree of significance in local ecological restoration programs. An analysis of molecular variance (AMOVA) of 100 amplified fragment length polymorphism (AFLP) markers revealed significant genetic differentiation among populations (ΦPT = 0.

Arabidopsis peroxisome proteomics.

The analytical depth of investigation of the peroxisomal proteome of the model plant Arabidopsis thaliana has not yet reached that of other major cellular organelles such as chloroplasts or mitochondria. This is primarily due to the difficulties associated with isolating and obtaining purified samples of peroxisomes from Arabidopsis. So far only a handful of research groups have been successful in obtaining such fractions.

Requirement for the plastidial oxidative pentose phosphate pathway for nitrate assimilation in Arabidopsis.

Sugar metabolism and the oxidative pentose phosphate pathway (OPPP) are strongly implicated in N assimilation, although the relationship between them and the roles of the plastidial and cytosolic OPPP have not been established genetically. We studied a knock-down mutant of the plastid-localized OPPP enzyme 6-phosphogluconolactonase 3 (PGL3). pgl3-1 plants exhibited relatively greater resource allocation to roots but were smaller than the wild type.

Conservation of two lineages of peroxisomal (Type I) 3-ketoacyl-CoA thiolases in land plants, specialization of the genes in Brassicaceae, and characterization of their expression in Arabidopsis thaliana.

Arabidopsis thaliana has three genes encoding type I 3-ketoacyl-CoA thiolases (KAT1, KAT2, and KAT5), one of which (KAT5) is alternatively transcribed to produce both peroxisomal and cytosolic proteins. To evaluate the potential importance of these four gene products, their evolutionary history in plants and their expression patterns in Arabidopsis were investigated. Land plants as a whole have gene lineages corresponding to KAT2 and KAT5, implying conservation of distinct functions for these two genes.

The Arabidopsis ortholog of rice DWARF27 acts upstream of MAX1 in the control of plant development by strigolactones.

Strigolactones (SLs) are carotenoid-derived plant hormones that regulate shoot branching, secondary growth, root development, and responses to soil phosphate. In Arabidopsis (Arabidopsis thaliana), SL biosynthesis requires the sequential action of two carotenoid cleavage dioxygenases, MORE AXILLARY GROWTH3 (MAX3) and MAX4, followed by a cytochrome P450, MAX1. In rice (Oryza sativa), the plastid-localized protein DWARF27 (OsD27) is also necessary for SL biosynthesis, but the equivalent gene in Arabidopsis has not been identified.

A collection of INDEL markers for map-based cloning in seven Arabidopsis accessions.

The availability of a comprehensive set of resources including an entire annotated reference genome, sequenced alternative accessions, and a multitude of marker systems makes Arabidopsis thaliana an ideal platform for genetic mapping. PCR markers based on INsertions/DELetions (INDELs) are currently the most frequently used polymorphisms. For the most commonly used mapping combination, Columbia×Landsberg erecta (Col-0×Ler-0), the Cereon polymorphism database is a valuable resource for the generation of polymorphic markers.

Signaling from the endoplasmic reticulum activates brassinosteroid signaling and promotes acclimation to stress in Arabidopsis.

The ability to acclimate to stresses enables plants to grow and develop under adverse environmental conditions. Regulated intramembrane proteolysis (RIP) triggered by endoplasmic reticulum (ER) stress mediates some forms of stress signaling. Brassinosteroids (BRs) have been implicated in plant adaptation to stress, but no mechanisms for activation have been discovered.

A nuclear-localized protein, KOLD SENSITIV-1, affects the expression of cold-responsive genes during prolonged chilling in Arabidopsis.

Plants respond to cold by transcriptional and metabolic responses which underlie tolerance and acclimation mechanisms, but details at the molecular level are incomplete. Here we describe KOLD SENSITIV-1 (KOS1), a new gene required for responses to cold. KOS1 protein is predicted to have coiled-coil, Structural Maintenance of Chromosomes and nuclear-targeting domains.

Phenotypic plasticity of adventitious rooting in Arabidopsis is controlled by complex regulation of AUXIN RESPONSE FACTOR transcripts and microRNA abundance.

The development of shoot-borne roots, or adventitious roots, is indispensable for mass propagation of elite genotypes. It is a complex genetic trait with a high phenotypic plasticity due to multiple endogenous and environmental regulatory factors. We demonstrate here that a subtle balance of activator and repressor AUXIN RESPONSE FACTOR (ARF) transcripts controls adventitious root initiation.

Identification of two Arabidopsis genes encoding a peroxisomal oxidoreductase-like protein and an acyl-CoA synthetase-like protein that are required for responses to pro-auxins.

Indole-3-butyric acid (IBA) and 2,4-dichlorophenoxybutyric acid (2,4-DB) are metabolised by peroxisomal beta-oxidation to active auxins that inhibit root growth. We screened Arabidopsis mutants for resistance to IBA and 2,4-DB and identified two new 2,4-DB resistant mutants. The mutant genes encode a putative oxidoreductase (SDRa) and a putative acyl-activating enzyme (AAE18).

Novel proteins, putative membrane transporters, and an integrated metabolic network are revealed by quantitative proteomic analysis of Arabidopsis cell culture peroxisomes.

Peroxisomes play key roles in energy metabolism, cell signaling, and plant development. A better understanding of these important functions will be achieved with a more complete definition of the peroxisome proteome. The isolation of peroxisomes and their separation from mitochondria and other major membrane systems have been significant challenges in the Arabidopsis (Arabidopsis thaliana) model system.

Alternative splicing of the Vupur3 transcript in cowpea produces multiple mRNA species with a single protein product that is present in both plastids and mitochondria.

A heterogeneous population of cDNAs (designated Vupur3) encoding phosphoribosylglycinamide formyltransferase (GART; EC 2.1.2.

Auxin and light control of adventitious rooting in Arabidopsis require ARGONAUTE1.

Adventitious rooting is a quantitative genetic trait regulated by both environmental and endogenous factors. To better understand the physiological and molecular basis of adventitious rooting, we took advantage of two classes of Arabidopsis thaliana mutants altered in adventitious root formation: the superroot mutants, which spontaneously make adventitious roots, and the argonaute1 (ago1) mutants, which unlike superroot are barely able to form adventitious roots. The defect in adventitious rooting observed in ago1 correlated with light hypersensitivity and the deregulation of auxin homeostasis specifically in the apical part of the seedlings.

Molecular phylogenetic analysis of the evolution of complex hybridity in Isotoma petraea.

Complex hybridity is a rare diploid genetic system of plants, extensively characterized in Oenothera, in which heterozygosity for one or more reciprocal translocations is maintained by means of autogamy and a balanced lethal system. It is visible at metaphase I of meiosis as rings or chains of chromosomes held together by terminalized chiasmata. Phylogenetic analysis based on 274 random amplified polymorphic DNA markers showed that in the Australian endemic Isotoma petraea (Lobeliaceae) the genetic system had a single origin, as a ring-of-six, in the Pigeon Rock population.

Effect of short-term N(2) deficiency on expression of the ureide pathway in cowpea root nodules.

Root systems of 28-d-old cowpea (Vigna unguiculata L. Walp cv Vita 3: Bradyrhizobium sp. strain CB756) plants bearing nitrogen-fixing nodules in sand culture were exposed to an atmosphere of Ar:O(2) (80:20, v/v) for 48 h and then returned to air.