Table of Contents

Aging in plants is an intricate process that balances vegetative growth with flowering and reproductive success. This work describes the identification of JUNGBRUNNEN1, a NAC transcription factor that regulates this process in Arabidopsis thaliana and additionally affects abiotic stress tolerance by activating expression of the DREB2A transcription factor.

Laser microdissection combined with Solexa sequencing of cDNA was used to analyze the transcriptome of the shoot meristem during the floral transition. Activated genes were placed in pathways downstream or parallel to the inductive signal encoded by FLOWERING LOCUS T.

Aging in plants is an intricate process that balances vegetative growth with flowering and reproductive success. This work describes the identification of JUNGBRUNNEN1, a NAC transcription factor that regulates this process in Arabidopsis thaliana and additionally affects abiotic stress tolerance by activating expression of the DREB2A transcription factor.

This work examines blue light–induced root phototropism, finding that it requires the phot1/NONPHOTOTROPIC HYPOCOTYL3 signaling pathway, which stimulates shootward auxin flux by changing PIN2 subcellular localization in the root apex transition zone.

This article shows that the phytochrome A photoreceptor promotes reorientation of the hypocotyl toward blue light (phototropism) by regulating the expression of nuclear genes. It also shows that phytochrome A nuclear signaling events still operate in a mutant where phytochrome A does not significantly accumulate in the nucleus.

ELF3 and ELF4 play pivotal roles in the circadian clock mechanism and in the integration of light signals to the clock, but the molecular basis of ELF3 and ELF4 action is poorly understood. This work uses multidisciplinary approaches to identify and characterize these clock factors as members of a dusk complex that works as a repressor to sustain rhythms of the circadian oscillator.

The visualization of storage, membrane, and signaling lipid species in embryos of cottonseeds at cellular resolution suggests that lipid species, even those in the same class, are distributed heterogeneously in tissues. This work provides new information about metabolite distribution and points to a previously unknown complexity in cellular biochemistry within plant tissues.

Auxin conjugation promotes susceptibility to pathogens. This study reveals that during infection with fungi and bacteria, auxin conjugation is increased in the plant to produce IAA-Asp, which regulates the expression of virulence genes and induces plant susceptibility to pathogens.

ELF3 and ELF4 play pivotal roles in the circadian clock mechanism and in the integration of light signals to the clock, but the molecular basis of ELF3 and ELF4 action is poorly understood. This work uses multidisciplinary approaches to identify and characterize these clock factors as members of a dusk complex that works as a repressor to sustain rhythms of the circadian oscillator.

In a genome-wide analysis of the transcriptional changes in Arabidopsis thaliana in response to Cu deficiency, about 13% are found to depend on the transcription factor SPL7. These include the genes encoding Cu(II) reductases FRO4 and FRO5, which are shown to act in high-affinity root Cu uptake. Severe physiological Cu deficiency results in a disruption of Fe homeostasis.

The work identifies maize PPR2263 and Arabidopsis thaliana MEF29 as orthologous mitochondrial RNA editing proteins, the first such orthologs shown to share target sites between a monocot and a dicot. In maize, the loss of editing of the cob transcript by PPR2263 causes the loss of a protein complex in the mitochondrial respiratory chain and ultimately slow growth of mutant plants.

This work identifies the SIP2 MAP kinase kinase as an interacting partner of the symbiosis receptor kinase SymRK. It shows that SymRK inhibits the kinase activity of SIP2 and establishes that a MAP kinase cascade plays a role in the signaling network leading to nodulation in legumes.

This work demonstrates that plant microsporocytes have specific meiosis initiation machinery by characterizing the rice CC-type glutaredoxin MICROSPORELESS1 (MIL1). The mil1 mutant shows defects both in the meiotic entry of sporogenous cell progenies and in the differentiation of surrounding somatic cell layers.

LST8 is a member of the widely conserved TOR kinase complex. This work shows that LST8 is important for plant growth as well as metabolic and developmental processes linked to changes in light conditions, probably by influencing the activity of the TOR complex.

This study demonstrates that sequence variation in the ligand-interacting degron modulates the stability of JAZ8 and, as a consequence, the extent to which JAZ8 represses jasmonate-responsive gene expression. This study also shows that JAZ8 is an EAR motif–containing protein that represses gene expression by direct recruitment of the corepressor TOPLESS to cognate transcription factors.

ELF3 and ELF4 play pivotal roles in the circadian clock mechanism and in the integration of light signals to the clock, but the molecular basis of ELF3 and ELF4 action is poorly understood. This work uses multidisciplinary approaches to identify and characterize these clock factors as members of a dusk complex that works as a repressor to sustain rhythms of the circadian oscillator.

The hyperaccumulation of micronutrients and toxic metals (such as zinc and cadmium, respectively) represents an extreme trait of metallophytes adapted to metal-rich environments. This work demonstrates that elevated production of the metal chelator nicotianamine, specifically in roots of the metallophyte Arabidopsis halleri, is important for efficient root-to-shoot translocation of zinc.

This study demonstrates that sequence variation in the ligand-interacting degron modulates the stability of JAZ8 and, as a consequence, the extent to which JAZ8 represses jasmonate-responsive gene expression. This study also shows that JAZ8 is an EAR motif–containing protein that represses gene expression by direct recruitment of the corepressor TOPLESS to cognate transcription factors.

In a genome-wide analysis of the transcriptional changes in Arabidopsis thaliana in response to Cu deficiency, about 13% are found to depend on the transcription factor SPL7. These include the genes encoding Cu(II) reductases FRO4 and FRO5, which are shown to act in high-affinity root Cu uptake. Severe physiological Cu deficiency results in a disruption of Fe homeostasis.

This work shows that suppressing the expression of the vesicle-inducing protein in plastids (VIPP1) in Chlamydomonas leads to aberrant structures at the origin of thylakoids and to structural defects particularly in photosystem II that render mutants sensitive to high light. The data indicate that VIPPs act in the biogenesis of thylakoid membrane core complexes, in particular the photosystems.

Laser microdissection combined with Solexa sequencing of cDNA was used to analyze the transcriptome of the shoot meristem during the floral transition. Activated genes were placed in pathways downstream or parallel to the inductive signal encoded by FLOWERING LOCUS T.

This work shows that suppressing the expression of the vesicle-inducing protein in plastids (VIPP1) in Chlamydomonas leads to aberrant structures at the origin of thylakoids and to structural defects particularly in photosystem II that render mutants sensitive to high light. The data indicate that VIPPs act in the biogenesis of thylakoid membrane core complexes, in particular the photosystems.

This article shows that the phytochrome A photoreceptor promotes reorientation of the hypocotyl toward blue light (phototropism) by regulating the expression of nuclear genes. It also shows that phytochrome A nuclear signaling events still operate in a mutant where phytochrome A does not significantly accumulate in the nucleus.

ELF3 and ELF4 play pivotal roles in the circadian clock mechanism and in the integration of light signals to the clock, but the molecular basis of ELF3 and ELF4 action is poorly understood. This work uses multidisciplinary approaches to identify and characterize these clock factors as members of a dusk complex that works as a repressor to sustain rhythms of the circadian oscillator.

This work identifies the SIP2 MAP kinase kinase as an interacting partner of the symbiosis receptor kinase SymRK. It shows that SymRK inhibits the kinase activity of SIP2 and establishes that a MAP kinase cascade plays a role in the signaling network leading to nodulation in legumes.

This article describes novel ways that algae may adjust metabolite trafficking when specific branches of fermentation metabolism are blocked. This rerouting of metabolites allows for continued glycolytic energy production under anoxic conditions, which is critical for the cell’s survival. Mechanisms associated with this reengineering of metabolism are almost completely unexplored.

This work finds that the photosystem II (PSII) assembly factor PratA from the cyanobacterium Synechocystis is involved in efficient delivery of manganese to PSII and is organized in distinct structures connecting plasma and thylakoid membranes. It proposes that initial steps of PSII assembly, including its preloading with manganese, take place at these PratA-dependent biogenesis centers.

The hyperaccumulation of micronutrients and toxic metals (such as zinc and cadmium, respectively) represents an extreme trait of metallophytes adapted to metal-rich environments. This work demonstrates that elevated production of the metal chelator nicotianamine, specifically in roots of the metallophyte Arabidopsis halleri, is important for efficient root-to-shoot translocation of zinc.

This work identifies jacalin-type lectin that is responsible for resistance to multiple plant viruses belonging to the genus Potexvirus. The isolation and characterization of this lectin sheds light on a novel resistance machinery to plant viruses.

Calcium- and calmodulin-dependent protein kinase (CCaMK) is a protein kinase that is crucial for plant-microbe symbioses. This work shows the importance of nuclear localization of CCaMK for its function in plant symbiotic responses. Moreover, activation of CCaMK in the nucleus induces cytological changes similar to those important for fungal infection, without presence of the symbiotic fungi.

This work implicates the Arabidopsis membrane protein ZIF1 in the vacuolar accumulation of the low molecular mass metal chelator nicotianamine. Precise regulation of intracellular nicotianamine distribution is critical for both Zn and Fe homeostasis as well as for the selective discrimination between these chemically similar micronutrients along the pathway of their movement inside the plant.

Cell wall and cellulose structure is imperative for proper cell elongation and, consequently, the architecture of plants, but components regulating cellulose structure are still elusive. This article shows that the secreted CTL1/POM1 and its close homolog CTL2 interact with glucan-based polymers and influence cellulose crystallinity and cell expansion.

This article shows that the phytochrome A photoreceptor promotes reorientation of the hypocotyl toward blue light (phototropism) by regulating the expression of nuclear genes. It also shows that phytochrome A nuclear signaling events still operate in a mutant where phytochrome A does not significantly accumulate in the nucleus.

This work finds that the photosystem II (PSII) assembly factor PratA from the cyanobacterium Synechocystis is involved in efficient delivery of manganese to PSII and is organized in distinct structures connecting plasma and thylakoid membranes. It proposes that initial steps of PSII assembly, including its preloading with manganese, take place at these PratA-dependent biogenesis centers.

This article shows that the phytochrome A photoreceptor promotes reorientation of the hypocotyl toward blue light (phototropism) by regulating the expression of nuclear genes. It also shows that phytochrome A nuclear signaling events still operate in a mutant where phytochrome A does not significantly accumulate in the nucleus.

This work identifies the SIP2 MAP kinase kinase as an interacting partner of the symbiosis receptor kinase SymRK. It shows that SymRK inhibits the kinase activity of SIP2 and establishes that a MAP kinase cascade plays a role in the signaling network leading to nodulation in legumes.

This work shows that the chloroplast-localized components of the chlorophyll catabolic pathway dynamically interact with each other, possibly forming a multiprotein complex specifically localizing to light-harvesting complex II. This interaction likely channels chlorophyll breakdown intermediates and thereby prevents potential chlorophyll-derived phototoxicity during leaf senescence.

In a genome-wide analysis of the transcriptional changes in Arabidopsis thaliana in response to Cu deficiency, about 13% are found to depend on the transcription factor SPL7. These include the genes encoding Cu(II) reductases FRO4 and FRO5, which are shown to act in high-affinity root Cu uptake. Severe physiological Cu deficiency results in a disruption of Fe homeostasis.

ELF3 and ELF4 play pivotal roles in the circadian clock mechanism and in the integration of light signals to the clock, but the molecular basis of ELF3 and ELF4 action is poorly understood. This work uses multidisciplinary approaches to identify and characterize these clock factors as members of a dusk complex that works as a repressor to sustain rhythms of the circadian oscillator.

This work presents a technology for effectively silencing endogenous small RNAs by expressing a small tandem target mimic (STTM) composed of two noncleavable small RNA binding sites linked by an empirically determined spacer. Expression of STTM in Arabidopsis thaliana leads to the specific degradation of endogenous small RNAs by small RNA degrading nuclease family enzymes.

Aging in plants is an intricate process that balances vegetative growth with flowering and reproductive success. This work describes the identification of JUNGBRUNNEN1, a NAC transcription factor that regulates this process in Arabidopsis thaliana and additionally affects abiotic stress tolerance by activating expression of the DREB2A transcription factor.

This work identifies the SIP2 MAP kinase kinase as an interacting partner of the symbiosis receptor kinase SymRK. It shows that SymRK inhibits the kinase activity of SIP2 and establishes that a MAP kinase cascade plays a role in the signaling network leading to nodulation in legumes.

Laser microdissection combined with Solexa sequencing of cDNA was used to analyze the transcriptome of the shoot meristem during the floral transition. Activated genes were placed in pathways downstream or parallel to the inductive signal encoded by FLOWERING LOCUS T.

ELF3 and ELF4 play pivotal roles in the circadian clock mechanism and in the integration of light signals to the clock, but the molecular basis of ELF3 and ELF4 action is poorly understood. This work uses multidisciplinary approaches to identify and characterize these clock factors as members of a dusk complex that works as a repressor to sustain rhythms of the circadian oscillator.

Cell wall and cellulose structure is imperative for proper cell elongation and, consequently, the architecture of plants, but components regulating cellulose structure are still elusive. This article shows that the secreted CTL1/POM1 and its close homolog CTL2 interact with glucan-based polymers and influence cellulose crystallinity and cell expansion.

This work proposes that the middle domain, which is distinct from the adaxial (upper) and abaxial (lower) domains, plays a key role in coordinating two important processes in early leaf development, blade outgrowth, and adaxial/abaxial patterning, through the actions of the middle domain–specific WOX genes, PRS and WOX1, in concert with the adaxial- and abaxial-specific genes.