Table of Contents

Pores called plasmodesmata that connect plant cells arise at cytokinesis and secondarily during wall extension. This work uses a range of imaging and computational approaches to show that secondary plasmodesmata arise in direct contact with existing plasmodesmata during radial wall extension.

This work uses genetic and biochemical assays to examine two RING-type E3 ligases that interact with and target a specific inhibitor of cyclin-dependent kinases, ICK4/KRP6, for proteasome-mediated degradation. This cell cycle inhibitor is expressed during gametophyte meiosis and must be degraded prior to the subsequent mitotic divisions that form the male and female gametophytes.

This work images phloem development using a remarkable improvement in plant tissue staining that, in combination with confocal microscopy, reveals three-dimensional cellular organization of plant tissue with a precision that formerly required tissue sectioning. Furthermore, coupled with staining for β-glucuronidase activity, this method shows gene expression with single-cell resolution.

This study reanalyzed channelrhodopsin-1 (CHR1)–based photocurrents in Chlamydomonas and demonstrated that, in addition to H⁺, ChR1 also conducts other cations. This conductance enables the alga to orient in the light even at alkaline pH.

Flavonoids have been shown to affect growth in a variety of plant species. This work demonstrates that changes in the Arabidopsis flavonol glycosylation profile can interfere with cell development, resulting in defects in cotyledon growth, pavement cell shape, stomatal development, and trichome formation.

Tandem affinity purification and mass spectrometry were used to identify a family of novel coiled-coil proteins required for nuclear envelope association of RanGAP1 in Arabidopsis root tip cells. The findings suggest an unanticipated complexity of RanGAP nuclear envelope targeting in higher plant cells, involving at least two families of likely plant-specific nuclear pore–associated proteins.

This study adopted a reverse genetics approach to provide evidence that two Arabidopsis xylosyltransferase genes are involved in xyloglucan biosynthesis in vivo. Disrupting both of these genes resulted in plants with a severe root hair phenotype that lacked detectable xyloglucan. These findings challenge conventional models of the plant primary cell wall.

Protein ubiquitination is a key posttranslational modification in eukaryotes. This study reveals a nuclear CULLIN4-based E3 ubiquitin ligase complex in Arabidopsis that plays a role in numerous plant developmental processes.

This work examines sequences critical for chloroplast protein import by alanine substitution mutagenesis of proteins with very different transit peptide sequences. This approach is complemented by bioinformatic grouping of peptides and motif identification within subgroups, producing a highly accurate algorithm to predict chloroplast localization.

Polyamines play a protective role against stress challenges in plants. This work shows that abiotic stress induces spermidine secretion into the apoplast, where it is oxidized by polyamine oxidase. Depending on its levels and those of intracellular polyamines, the generated H₂O₂ induces either tolerance events or programmed cell death.

Flavonoids have been shown to affect growth in a variety of plant species. This work demonstrates that changes in the Arabidopsis flavonol glycosylation profile can interfere with cell development, resulting in defects in cotyledon growth, pavement cell shape, stomatal development, and trichome formation.

Protein ubiquitination is a key posttranslational modification in eukaryotes. This study reveals a nuclear CULLIN4-based E3 ubiquitin ligase complex in Arabidopsis that plays a role in numerous plant developmental processes.

Flavonoids have been shown to affect growth in a variety of plant species. This work demonstrates that changes in the Arabidopsis flavonol glycosylation profile can interfere with cell development, resulting in defects in cotyledon growth, pavement cell shape, stomatal development, and trichome formation.

Drought-inducible gene expression is controlled by the key transcription factor DREB2A. We identified two C3HC4 RING domain–containing proteins that interact with DREB2A and function as E3 ubiquitin ligases to mediate DREB2A degradation to tightly control DREB2A protein abundance.

This study reanalyzed channelrhodopsin-1 (CHR1)–based photocurrents in Chlamydomonas and demonstrated that, in addition to H⁺, ChR1 also conducts other cations. This conductance enables the alga to orient in the light even at alkaline pH.

BARD1 represses the transcriptional activity of WUSCHEL, a gene essential for maintenance of stem cell fate in Arabidopsis. In a bard1-null mutant, severe shoot apical meristem defects are observed as a result of WUSCHEL expression outside of the meristem organizing center. BARD1 may inhibit a chromatin-remodeling process vital for WUS expression.

This study reanalyzed channelrhodopsin-1 (CHR1)–based photocurrents in Chlamydomonas and demonstrated that, in addition to H⁺, ChR1 also conducts other cations. This conductance enables the alga to orient in the light even at alkaline pH.

This work describes the identification of a plant glycosyltransferase that is involved in the initial phase of N-glycan biosynthesis in the endoplasmic reticulum. A detailed analysis of a mutant of this glycosyltransferase provides insights into properties of downstream enzymes in the N-glycan biosynthesis pathway in plants.

This study adopted a reverse genetics approach to provide evidence that two Arabidopsis xylosyltransferase genes are involved in xyloglucan biosynthesis in vivo. Disrupting both of these genes resulted in plants with a severe root hair phenotype that lacked detectable xyloglucan. These findings challenge conventional models of the plant primary cell wall.

This work examines sequences critical for chloroplast protein import by alanine substitution mutagenesis of proteins with very different transit peptide sequences. This approach is complemented by bioinformatic grouping of peptides and motif identification within subgroups, producing a highly accurate algorithm to predict chloroplast localization.

Flavonoids have been shown to affect growth in a variety of plant species. This work demonstrates that changes in the Arabidopsis flavonol glycosylation profile can interfere with cell development, resulting in defects in cotyledon growth, pavement cell shape, stomatal development, and trichome formation.

This work examines sequences critical for chloroplast protein import by alanine substitution mutagenesis of proteins with very different transit peptide sequences. This approach is complemented by bioinformatic grouping of peptides and motif identification within subgroups, producing a highly accurate algorithm to predict chloroplast localization.

This work describes the identification of a plant glycosyltransferase that is involved in the initial phase of N-glycan biosynthesis in the endoplasmic reticulum. A detailed analysis of a mutant of this glycosyltransferase provides insights into properties of downstream enzymes in the N-glycan biosynthesis pathway in plants.

This study adopted a reverse genetics approach to provide evidence that two Arabidopsis xylosyltransferase genes are involved in xyloglucan biosynthesis in vivo. Disrupting both of these genes resulted in plants with a severe root hair phenotype that lacked detectable xyloglucan. These findings challenge conventional models of the plant primary cell wall.

BARD1 represses the transcriptional activity of WUSCHEL, a gene essential for maintenance of stem cell fate in Arabidopsis. In a bard1-null mutant, severe shoot apical meristem defects are observed as a result of WUSCHEL expression outside of the meristem organizing center. BARD1 may inhibit a chromatin-remodeling process vital for WUS expression.

This work uses genetic and biochemical assays to examine two RING-type E3 ligases that interact with and target a specific inhibitor of cyclin-dependent kinases, ICK4/KRP6, for proteasome-mediated degradation. This cell cycle inhibitor is expressed during gametophyte meiosis and must be degraded prior to the subsequent mitotic divisions that form the male and female gametophytes.

This study reanalyzed channelrhodopsin-1 (CHR1)–based photocurrents in Chlamydomonas and demonstrated that, in addition to H⁺, ChR1 also conducts other cations. This conductance enables the alga to orient in the light even at alkaline pH.

Drought-inducible gene expression is controlled by the key transcription factor DREB2A. We identified two C3HC4 RING domain–containing proteins that interact with DREB2A and function as E3 ubiquitin ligases to mediate DREB2A degradation to tightly control DREB2A protein abundance.

Protein ubiquitination is a key posttranslational modification in eukaryotes. This study reveals a nuclear CULLIN4-based E3 ubiquitin ligase complex in Arabidopsis that plays a role in numerous plant developmental processes.

Tandem affinity purification and mass spectrometry were used to identify a family of novel coiled-coil proteins required for nuclear envelope association of RanGAP1 in Arabidopsis root tip cells. The findings suggest an unanticipated complexity of RanGAP nuclear envelope targeting in higher plant cells, involving at least two families of likely plant-specific nuclear pore–associated proteins.

This work describes the identification of a plant glycosyltransferase that is involved in the initial phase of N-glycan biosynthesis in the endoplasmic reticulum. A detailed analysis of a mutant of this glycosyltransferase provides insights into properties of downstream enzymes in the N-glycan biosynthesis pathway in plants.

Polyamines play a protective role against stress challenges in plants. This work shows that abiotic stress induces spermidine secretion into the apoplast, where it is oxidized by polyamine oxidase. Depending on its levels and those of intracellular polyamines, the generated H₂O₂ induces either tolerance events or programmed cell death.

Mitochondrial fission is a fundamental but poorly understood process in plant cells. DYNAMIN-RELATED PROTEIN3A is a conserved eukaryotic mitochondrial fission factor found in Arabidopsis that forms a ring around and severs mitochondria. Here, we identify a novel plant-specific factor, ELONGATED MITOCHONDRIA1, that is required for the correct localization of DRP3A.

Polyamines play a protective role against stress challenges in plants. This work shows that abiotic stress induces spermidine secretion into the apoplast, where it is oxidized by polyamine oxidase. Depending on its levels and those of intracellular polyamines, the generated H₂O₂ induces either tolerance events or programmed cell death.

This work uses genetic and biochemical assays to examine two RING-type E3 ligases that interact with and target a specific inhibitor of cyclin-dependent kinases, ICK4/KRP6, for proteasome-mediated degradation. This cell cycle inhibitor is expressed during gametophyte meiosis and must be degraded prior to the subsequent mitotic divisions that form the male and female gametophytes.

This study adopted a reverse genetics approach to provide evidence that two Arabidopsis xylosyltransferase genes are involved in xyloglucan biosynthesis in vivo. Disrupting both of these genes resulted in plants with a severe root hair phenotype that lacked detectable xyloglucan. These findings challenge conventional models of the plant primary cell wall.

This study examines the molecular interactions of PEROXIN11 isoforms with each other, with FISSION1 isoforms, and with DYNAMIN-RELATED PROTEIN3A (DRP3A) in peroxisome replication during cell division. Gene silencing and protein interaction experiments show that these proteins play distinct but overlapping roles in the elongation and fission of replicating peroxisomes.

This work describes the identification of a plant glycosyltransferase that is involved in the initial phase of N-glycan biosynthesis in the endoplasmic reticulum. A detailed analysis of a mutant of this glycosyltransferase provides insights into properties of downstream enzymes in the N-glycan biosynthesis pathway in plants.

Mitochondrial fission is a fundamental but poorly understood process in plant cells. DYNAMIN-RELATED PROTEIN3A is a conserved eukaryotic mitochondrial fission factor found in Arabidopsis that forms a ring around and severs mitochondria. Here, we identify a novel plant-specific factor, ELONGATED MITOCHONDRIA1, that is required for the correct localization of DRP3A.

Golgi stacks in Arabidopsis seed coat cells produce mucilage synchronously at a specific stage of differentiation. The morphology of stacks was dependent on the volume of mucilage produced, but the number was not, suggesting that proliferation of stacks is developmentally programmed. Mucilage-producing Golgi stacks were randomly distributed in the cell and not clustered at the site of secretion.

Drought-inducible gene expression is controlled by the key transcription factor DREB2A. We identified two C3HC4 RING domain–containing proteins that interact with DREB2A and function as E3 ubiquitin ligases to mediate DREB2A degradation to tightly control DREB2A protein abundance.

This work describes the identification of a plant glycosyltransferase that is involved in the initial phase of N-glycan biosynthesis in the endoplasmic reticulum. A detailed analysis of a mutant of this glycosyltransferase provides insights into properties of downstream enzymes in the N-glycan biosynthesis pathway in plants.

Several types of self-protecting systems that involve hormone signaling allow plants to survive various types of external stresses. This work details antagonistic interactions between abscisic acid–mediated responses to environmental stresses and salicylic acid–mediated signaling in the induction of systemic acquired resistance to pathogens.

This work uses genetic and biochemical assays to examine two RING-type E3 ligases that interact with and target a specific inhibitor of cyclin-dependent kinases, ICK4/KRP6, for proteasome-mediated degradation. This cell cycle inhibitor is expressed during gametophyte meiosis and must be degraded prior to the subsequent mitotic divisions that form the male and female gametophytes.