Table of Contents
IN BRIEF
LARGE-SCALE BIOLOGY ARTICLES
Genome-Wide Analysis of Alternative Splicing in Zea mays: Landscape and Genetic RegulationThis work examines alternative splicing (AS) of pre-mRNA in maize, revealing thousands of new isoforms from intron-containing genes, some of which encode entirely different proteins from their closest known isoforms. Analysis of these isoforms and identification of genomic loci that regulate AS highlight the important role that AS plays in tissue identity and genotypic variation in maize.
RESEARCH ARTICLES
Genome-Wide Study of KNOX Regulatory Network Reveals Brassinosteroid Catabolic Genes Important for Shoot Meristem Function in RiceGain- and loss-of-function studies revealed that the rice KNOX transcription factor OSH1 negatively regulates the brassinosteroid (BR) phytohormone pathway. Genomics approaches identified BR catabolism genes as direct targets of OSH1 in the shoot meristems. RNAi knockdown studies suggested that BR catabolism is important for shoot meristem function and for regulation of panicle branch angle.
ROP3 GTPase Contributes to Polar Auxin Transport and Auxin Responses and Is Important for Embryogenesis and Seedling Growth in ArabidopsisThis work identifies the role of ROP3 GTPase in embryo development and auxin-dependent plant growth and shows that ROP3 is important to maintain the proper polarity of auxin efflux carriers PIN1 and PIN3 at the plasma membrane. The results link cell polarity to auxin-dependent patterning through the activity of ROP3.
MYB118 Represses Endosperm Maturation in Seeds of ArabidopsisStorage compounds like oil and storage proteins accumulate both in the endosperm and in the embryo of Arabidopsis seeds. The MYB118 transcription factor is specifically expressed in the endosperm and represses storage compound synthesis in this tissue, thus contributing to establishment of the embryo as the main deposition site for reserves in the seed.
Overexpression of the Tomato Pollen Receptor Kinase LePRK1 Rewires Pollen Tube Growth to a Blebbing ModePollen tubes are tubular structures that extend by tip growth. Upon overexpression of merely a single endogenous molecule, LePRK1, or a portion of it lacking its extracellular domain, pollen tube cells switched to an alternative mechanism for extension of the leading edge that is analogous to the blebbing growth mode reported for Dictyostelium and for Drosophila stem cells.
Hypomethylated Pollen Bypasses the Interploidy Hybridization Barrier in ArabidopsisPaternal hypomethylation can bypass the interploidy hybridization barrier by alleviating the requirement for the epigenetic Polycomb Repressive Complex 2 (PRC2) in the endosperm. The hypomethylated pollen genome causes de novo CHG methylation directed to FIS-PRC2 target genes, suggesting that different epigenetic modifications can functionally substitute for each other.
ABCG Transporters Are Required for Suberin and Pollen Wall Extracellular Barriers in ArabidopsisPlants make tough barriers outside their cells in precise anatomical locations to control water and solute movement through their tissues. This work demonstrates that a family of transport proteins is required in Arabidopsis to form such barriers in roots and in seed coats and to make a functional pollen wall.
BBX19 Interacts with CONSTANS to Repress FLOWERING LOCUS T Transcription, Defining a Flowering Time Checkpoint in ArabidopsisBBX19, a transcription factor with two B-Box motifs, is a clock output component that functions as a flowering time checkpoint by physically interacting with CO and depleting the CO pool required for FT activation. The integrity of the Box1 motif is necessary for the functionality of BBX19.
Structural Basis for the Oligomerization of the MADS Domain Transcription Factor SEPALLATA3 in ArabidopsisThe structure of the keratin-like domain of SEPALLATA3, a MADS transcription factor involved in floral organ development, was solved to 2.5 Å by x-ray crystallography. The structure shows a novel oligomerization interface formed by two alpha helices oriented approximately 90° apart. Dimerization occurs through interactions of helix 1, and tetramerization occurs through interactions of helix 2.
Resolving Distinct Genetic Regulators of Tomato Leaf Shape within a Heteroblastic and Ontogenetic ContextLeaf shape is dynamic and influenced by numerous factors. Here, the authors quantify shape differences in leaves across the leaf series and during their development, determining their genetic basis and the effects of environment, in a population resulting from a cross between tomato and a wild desert relative.
Arabidopsis DE-ETIOLATED1 Represses Photomorphogenesis by Positively Regulating Phytochrome-Interacting Factors in the DarkLight is a critically important environmental signal regulating plant development, and several repressors have been identified that can inhibit plant photomorphogenesis in the dark. This study reveals a possible mechanism by which two groups of repressors, COP/DET/FUS and PIFs, work in concert to repress photomorphogenesis in darkness.
The Light-Harvesting Chlorophyll a/b Binding Proteins Lhcb1 and Lhcb2 Play Complementary Roles during State Transitions in ArabidopsisArabidopsis lines lacking either light-harvesting complex (LHC) protein Lhcb1 or Lhcb2 were produced, revealing that Lhcb1 and Lhcb2 play different roles during state transitions and that both are necessary but neither is sufficient. Plant lacking Lhcb1 lacked most LHCII trimers but plants lacking Lhcb2 contained LHCII similar to the wild type but could not perform state transitions.
The Small Regulatory RNA SyR1/PsrR1 Controls Photosynthetic Functions in CyanobacteriaThis work describes the role of a small noncoding RNA in the regulation of photosynthetic gene expression in cyanobacteria. Advanced computational target prediction combined with extensive experimental data reveal the photosynthesis regulatory RNA 1 as a key modulator of photosynthetic functions upon high-light exposure.
Arabidopsis thaliana RNase H2 Deficiency Counteracts the Needs for the WEE1 Checkpoint Kinase but Triggers Genome InstabilityAbsence of the RNAse H2 complex, mediating the excision of ribonucleotides from DNA, was found to overcome the growth inhibitory phenotype of plants lacking a functional replication checkpoint because of tolerating the substitution of deoxynucleotides with ribonucleotides. This substitution, however, results in replication errors, demonstrating the need of RNase H2 activity for genome stability.
How Vacuolar Sorting Receptor Proteins Interact with Their Cargo Proteins: Crystal Structures of Apo and Cargo-Bound Forms of the Protease-Associated Domain from an Arabidopsis Vacuolar Sorting ReceptorThis work explores how vacuolar sorting receptor (VSR) recognizes sequence-specific information on cargo proteins for targeting to the vacuole. Elucidation of the structures of the protease-associated domain of a VSR with and without its cognate cargo peptide, along with mutagenesis and functional studies, provides insights into how VSR recognizes its cargo proteins.
Structural Studies of Cinnamoyl-CoA Reductase and Cinnamyl-Alcohol Dehydrogenase, Key Enzymes of Monolignol BiosynthesisThe enzymes cinnamoyl-CoA reductase and cinnamyl-alcohol dehydrogenase participate in the generation of building blocks for plant lignin-polymers. Their structures reported here shed light on the mechanisms of enzyme activity and regulation and on the determinants of substrate specificity. These findings may ultimately aid in the rational engineering of lignin composition in plants.
Spatio-Temporal Dynamics of Fructan Metabolism in Developing Barley GrainsFructan metabolism in barley grains is developmental stage and tissue specific. Levans/graminans accumulate in the cellularized endosperm at the prestorage phase, while inulins are enriched in the transfer tissues around the endosperm cavity at the storage phase. This tight partitioning suggests that different fructans have distinct functions in various tissues during barley grain development.
A Root-Expressed l-Phenylalanine:4-Hydroxyphenylpyruvate Aminotransferase Is Required for Tropane Alkaloid Biosynthesis in Atropa belladonnaThis work helps uncover the biosynthetic pathway of the medicinally important tropane alkaloids in Deadly Nightshade. Transcriptomics, silencing, and biochemical analysis reveal the phylogenetically distinct, root-specific aromatic amino acid aminotransferase Ab-ArAT4, which preferentially catalyzes the first step in the formation of littorine, a key intermediate in tropane alkaloid biosynthesis.
Sterol Side Chain Reductase 2 Is a Key Enzyme in the Biosynthesis of Cholesterol, the Common Precursor of Toxic Steroidal Glycoalkaloids in PotatoThis work elucidates the biosynthetic pathway of toxic steroidal glycoalkaloids (SGAs) in potato, revealing that sterol side chain reductase 2 (SSR2) functions as a key enzyme in the biosynthesis of cholesterol and related SGAs. Silencing or disrupting SSR2 yielded potatoes with significantly reduced cholesterol and SGA levels but normal plant growth, making SSR2 an excellent target for breeding.
Phenylcoumaran Benzylic Ether Reductase Prevents Accumulation of Compounds Formed under Oxidative Conditions in Poplar XylemThis work reveals the biological function of phenylcoumaran benzylic ether reductase, one of the most abundant proteins in poplar wood. Its role is to reduce monolignol coupling products and to prevent accumulation of compounds formed under oxidative conditions.
Multiple N-Glycans Cooperate in the Subcellular Targeting and Functioning of Arabidopsis KORRIGAN1Arabidopsis KORRIGAN1 is a membrane protein with a heavily N-glycosylated extracellular domain. Conserved N-glycosylation sites support the trans-Golgi network localization and in vivo function of KORRIGAN1 at the plasma membrane. The host cell’s capacity to produce complex N-glycans affects KORRIGAN1 function in trans.
Adjustment of Host Cells for Accommodation of Symbiotic Bacteria: Vacuole Defunctionalization, HOPS Suppression, and TIP1g Retargeting in MedicagoThe accommodation of thousands of nitrogen-fixing rhizobia in legume root nodules requires changes in functionality of the vacuoles of infected cells. Suppression of HOPS tethering complex genes and tonoplast aquaporin retargeting to symbiosomes is part of the underlying mechanism. Defunctionalization of host vacuoles contributes to the expansion and maintenance of intracellular rhizobia.
