Table of Contents

Leaf variegation has long been recognized as a genetic trait, but the question remains as to why and how green and white sectors are formed in the same leaf in a uniform genetic background. In this work, identification of trans-acting mutations that suppress leaf variegation in an Arabidopsis mutant demonstrates a mechanism for variegation associated with chloroplast activities.

Substoichiometric shifting (SSS) is the amplification or suppression of subgenomic molecules in plant mitochondrial genomes. This report describes two nuclear genes, MSH1 and RECA3, that regulate SSS in Arabidopsis by controlling illegitimate recombination and presents the cellular and developmental implications of msh1 and recA3 mutant-associated mitochondrial genome instability in plants.

G proteins are important signaling molecules in plants and animal systems. This work provides evidence that plant heterotrimeric G proteins use both Gγ subunits to convey functional selectivity to the Gβγ dimers and reveals a mechanism underlying the complexity of G protein–mediated signaling in plants.

Low temperatures initiate signaling pathways that control gene expression necessary for cold acclimation and chilling and freezing tolerances. This work establishes that SIZ1 is a regulator of cold acclimation through sumoylation of ICE1, which induces expression of CBF/DREB1 and its regulon and facilitates freezing tolerance.

Functionally equivalent genes often display spatial and temporal differences in transcriptional regulation but may also have unique functions. As shown here, the similar calcium binding proteins SCABP8 and SOS3 protect shoot and root tissues, respectively, from salt stress by activating and recruiting the SOS2 kinase, but they also differ in additional regulatory mechanisms specific to each protein.

G proteins are important signaling molecules in plants and animal systems. This work provides evidence that plant heterotrimeric G proteins use both Gγ subunits to convey functional selectivity to the Gβγ dimers and reveals a mechanism underlying the complexity of G protein–mediated signaling in plants.

Arabidopsis cyclin-dependent kinase CDKC;2 and its cyclin T partner CYCT1;5 encode two interacting proteins that form a complex with an important role in cauliflower mosaic virus (CaMV) infection. This report establishes these CDKC kinase complexes as important host targets of CaMV for transcriptional activation of viral genes and critical regulators of plant growth and development.

In plants, the proper decision to germinate is critical for plant survival. Light promotes seed germination by removing PIL5, a phytochrome-interacting light-labile bHLH transcription factor. It is shown here that PIL5 regulates gibberellin (GA) signaling genes by directly binding to their promoters and that PIL5-mediated light signaling regulates not only GA but also abscisic acid metabolism.

Legume/rhizobial symbiosis is a key player in the global nitrogen cycle by fixing atmospheric nitrogen. Recognition of bacteria by legumes requires the bacterial signaling molecule Nod factor, which induces early plant root responses in nodulation. This work identifies the transcription factor ERF Required for Nodulation as an important component of the Nod factor signal transduction pathway.

Legume/rhizobial symbiosis is a key player in the global nitrogen cycle by fixing atmospheric nitrogen. Recognition of bacteria by legumes requires the bacterial signaling molecule Nod factor, which induces early plant root responses in nodulation. This work identifies the transcription factor ERF Required for Nodulation as an important component of the Nod factor signal transduction pathway.

Class E vacuolar protein sorting (VPS) proteins function in endosomal sorting of secretory and endocytic cargo. This work identifies an Arabidopsis homolog of the yeast and mammalian VPS4 protein, SUPPRESSOR OF K⁺ TRANSPORT GROWTH DEFECT1 (SKD1), which localizes to the cytoplasm and endosomes. In addition, LYST-INTERACTING PROTEIN5 is identified as a strong positive regulator of SKD1 ATPase activity.

Systemic infection by viruses requires proper processing and transport of viral RNA throughout the plant. This work demonstrates that Brome mosaic virus RNA can traffic long distances through the phloem independent of replication. Viral movement protein and coat proteins may increase the efficiency of trafficking but are not essential for the trafficking event.

The modulation of chromatin structure is mediated by enzymes such as histone acetyltransferases and deacetylases (HDACs). This functional characterization of a maize HDAC, HDA101, shows that it reversibly regulates histone acetylation, thus controlling gene and repeat activity, setting the histone code, and modulating developmental programs.

The modulation of chromatin structure is mediated by enzymes such as histone acetyltransferases and deacetylases (HDACs). This functional characterization of a maize HDAC, HDA101, shows that it reversibly regulates histone acetylation, thus controlling gene and repeat activity, setting the histone code, and modulating developmental programs.

The protective role of a plant's cuticle in abiotic stress and biotic interactions depends on its permeability. These results suggest that the transcription factor WAX INDUCER1 controls cuticle formation by directly or collaboratively activating the transcription of cutin biosynthesis genes and modulates cuticle permeability through its influence on cutin composition.

Low temperatures initiate signaling pathways that control gene expression necessary for cold acclimation and chilling and freezing tolerances. This work establishes that SIZ1 is a regulator of cold acclimation through sumoylation of ICE1, which induces expression of CBF/DREB1 and its regulon and facilitates freezing tolerance.

In plants, the proper decision to germinate is critical for plant survival. Light promotes seed germination by removing PIL5, a phytochrome-interacting light-labile bHLH transcription factor. It is shown here that PIL5 regulates gibberellin (GA) signaling genes by directly binding to their promoters and that PIL5-mediated light signaling regulates not only GA but also abscisic acid metabolism.

Systemic infection by viruses requires proper processing and transport of viral RNA throughout the plant. This work demonstrates that Brome mosaic virus RNA can traffic long distances through the phloem independent of replication. Viral movement protein and coat proteins may increase the efficiency of trafficking but are not essential for the trafficking event.

Leaf senescence involves degradation of photosynthetic pigments, proteins, and chloroplasts. This work finds that defects in a possible chlorophyll b reductase, the first enzyme in chlorophyll b degradation, inhibit LHCII and grana degradation in leaf senescence and result in a stay-green phenotype, suggesting that chlorophyll b degradation might be an important regulatory point in leaf senescence.

Legume/rhizobial symbiosis is a key player in the global nitrogen cycle by fixing atmospheric nitrogen. Recognition of bacteria by legumes requires the bacterial signaling molecule Nod factor, which induces early plant root responses in nodulation. This work identifies the transcription factor ERF Required for Nodulation as an important component of the Nod factor signal transduction pathway.

D-type cyclins play an essential role in cell cycle progression in response to external signals. This study demonstrates a specific requirement of cyclin D in cell divisions associated with stomatal precursor formation in the hypocotyl.

In plants, the proper decision to germinate is critical for plant survival. Light promotes seed germination by removing PIL5, a phytochrome-interacting light-labile bHLH transcription factor. It is shown here that PIL5 regulates gibberellin (GA) signaling genes by directly binding to their promoters and that PIL5-mediated light signaling regulates not only GA but also abscisic acid metabolism.

Functionally equivalent genes often display spatial and temporal differences in transcriptional regulation but may also have unique functions. As shown here, the similar calcium binding proteins SCABP8 and SOS3 protect shoot and root tissues, respectively, from salt stress by activating and recruiting the SOS2 kinase, but they also differ in additional regulatory mechanisms specific to each protein.

The modulation of chromatin structure is mediated by enzymes such as histone acetyltransferases and deacetylases (HDACs). This functional characterization of a maize HDAC, HDA101, shows that it reversibly regulates histone acetylation, thus controlling gene and repeat activity, setting the histone code, and modulating developmental programs.

Substoichiometric shifting (SSS) is the amplification or suppression of subgenomic molecules in plant mitochondrial genomes. This report describes two nuclear genes, MSH1 and RECA3, that regulate SSS in Arabidopsis by controlling illegitimate recombination and presents the cellular and developmental implications of msh1 and recA3 mutant-associated mitochondrial genome instability in plants.

Legume/rhizobial symbiosis is a key player in the global nitrogen cycle by fixing atmospheric nitrogen. Recognition of bacteria by legumes requires the bacterial signaling molecule Nod factor, which induces early plant root responses in nodulation. This work identifies the transcription factor ERF Required for Nodulation as an important component of the Nod factor signal transduction pathway.

G proteins are important signaling molecules in plants and animal systems. This work provides evidence that plant heterotrimeric G proteins use both Gγ subunits to convey functional selectivity to the Gβγ dimers and reveals a mechanism underlying the complexity of G protein–mediated signaling in plants.

Photosystem II is a genetic mosaic consisting of plastid- and nuclear-encoded subunits requiring coordinated gene expression in both compartments. This work finds that the nuclear-encoded factor HIGH CHLOROPHYLL FLUORESCENCE 173 is essential for photosystem II biogenesis. Lack of the protein results in drastically reduced D1 synthesis due to decreased translation of the psbA mRNA.

Legume/rhizobial symbiosis is a key player in the global nitrogen cycle by fixing atmospheric nitrogen. Recognition of bacteria by legumes requires the bacterial signaling molecule Nod factor, which induces early plant root responses in nodulation. This work identifies the transcription factor ERF Required for Nodulation as an important component of the Nod factor signal transduction pathway.

Leaf variegation has long been recognized as a genetic trait, but the question remains as to why and how green and white sectors are formed in the same leaf in a uniform genetic background. In this work, identification of trans-acting mutations that suppress leaf variegation in an Arabidopsis mutant demonstrates a mechanism for variegation associated with chloroplast activities.

Low temperatures initiate signaling pathways that control gene expression necessary for cold acclimation and chilling and freezing tolerances. This work establishes that SIZ1 is a regulator of cold acclimation through sumoylation of ICE1, which induces expression of CBF/DREB1 and its regulon and facilitates freezing tolerance.

The modulation of chromatin structure is mediated by enzymes such as histone acetyltransferases and deacetylases (HDACs). This functional characterization of a maize HDAC, HDA101, shows that it reversibly regulates histone acetylation, thus controlling gene and repeat activity, setting the histone code, and modulating developmental programs.

D-type cyclins play an essential role in cell cycle progression in response to external signals. This study demonstrates a specific requirement of cyclin D in cell divisions associated with stomatal precursor formation in the hypocotyl.

In plants, the proper decision to germinate is critical for plant survival. Light promotes seed germination by removing PIL5, a phytochrome-interacting light-labile bHLH transcription factor. It is shown here that PIL5 regulates gibberellin (GA) signaling genes by directly binding to their promoters and that PIL5-mediated light signaling regulates not only GA but also abscisic acid metabolism.

Photosystem II is a genetic mosaic consisting of plastid- and nuclear-encoded subunits requiring coordinated gene expression in both compartments. This work finds that the nuclear-encoded factor HIGH CHLOROPHYLL FLUORESCENCE 173 is essential for photosystem II biogenesis. Lack of the protein results in drastically reduced D1 synthesis due to decreased translation of the psbA mRNA.

The protective role of a plant's cuticle in abiotic stress and biotic interactions depends on its permeability. These results suggest that the transcription factor WAX INDUCER1 controls cuticle formation by directly or collaboratively activating the transcription of cutin biosynthesis genes and modulates cuticle permeability through its influence on cutin composition.

The widely distributed DEGP proteases play important roles in the degradation of damaged and misfolded proteins. This report reveals that Arabidopsis DEG5 and DEG8 form a hexamer in the thylakoid lumen and are important for efficient turnover of the photosystem II D1 protein and for protection against photoinhibition in vivo.

The modulation of chromatin structure is mediated by enzymes such as histone acetyltransferases and deacetylases (HDACs). This functional characterization of a maize HDAC, HDA101, shows that it reversibly regulates histone acetylation, thus controlling gene and repeat activity, setting the histone code, and modulating developmental programs.

The protective role of a plant's cuticle in abiotic stress and biotic interactions depends on its permeability. These results suggest that the transcription factor WAX INDUCER1 controls cuticle formation by directly or collaboratively activating the transcription of cutin biosynthesis genes and modulates cuticle permeability through its influence on cutin composition.

Leaf senescence involves degradation of photosynthetic pigments, proteins, and chloroplasts. This work finds that defects in a possible chlorophyll b reductase, the first enzyme in chlorophyll b degradation, inhibit LHCII and grana degradation in leaf senescence and result in a stay-green phenotype, suggesting that chlorophyll b degradation might be an important regulatory point in leaf senescence.

Photosystem II is a genetic mosaic consisting of plastid- and nuclear-encoded subunits requiring coordinated gene expression in both compartments. This work finds that the nuclear-encoded factor HIGH CHLOROPHYLL FLUORESCENCE 173 is essential for photosystem II biogenesis. Lack of the protein results in drastically reduced D1 synthesis due to decreased translation of the psbA mRNA.

Substoichiometric shifting (SSS) is the amplification or suppression of subgenomic molecules in plant mitochondrial genomes. This report describes two nuclear genes, MSH1 and RECA3, that regulate SSS in Arabidopsis by controlling illegitimate recombination and presents the cellular and developmental implications of msh1 and recA3 mutant-associated mitochondrial genome instability in plants.

Legume/rhizobial symbiosis is a key player in the global nitrogen cycle by fixing atmospheric nitrogen. Recognition of bacteria by legumes requires the bacterial signaling molecule Nod factor, which induces early plant root responses in nodulation. This work identifies the transcription factor ERF Required for Nodulation as an important component of the Nod factor signal transduction pathway.

In plants, the proper decision to germinate is critical for plant survival. Light promotes seed germination by removing PIL5, a phytochrome-interacting light-labile bHLH transcription factor. It is shown here that PIL5 regulates gibberellin (GA) signaling genes by directly binding to their promoters and that PIL5-mediated light signaling regulates not only GA but also abscisic acid metabolism.

Leaf senescence involves degradation of photosynthetic pigments, proteins, and chloroplasts. This work finds that defects in a possible chlorophyll b reductase, the first enzyme in chlorophyll b degradation, inhibit LHCII and grana degradation in leaf senescence and result in a stay-green phenotype, suggesting that chlorophyll b degradation might be an important regulatory point in leaf senescence.

Photosystem II is a genetic mosaic consisting of plastid- and nuclear-encoded subunits requiring coordinated gene expression in both compartments. This work finds that the nuclear-encoded factor HIGH CHLOROPHYLL FLUORESCENCE 173 is essential for photosystem II biogenesis. Lack of the protein results in drastically reduced D1 synthesis due to decreased translation of the psbA mRNA.