Table of Contents
IN BRIEF
PERSPECTIVE
RESEARCH ARTICLES
- Differentiating Arabidopsis Shoots from Leaves by Combined YABBY Activities
YABBY activity is required in seed plants for specification of leaves and the origin of the YABBY genes coincides with the origin of seed plant leaves. This work probes the role of YABBY genes in molding shoot programs into laminar organs by examining shoot and leaf development in plants mutant for four vegetative YABBY genes.
- Expression of SHOOT MERISTEMLESS, WUSCHEL, and ASYMMETRIC LEAVES1 Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis
This work explores how organogenesis of the shoot apical meristem (SAM)-less shoots evolved from that of the typical SAM-mediated shoots in the aquatic eudicot Podostemaceae. Based on the expression patterns of STM, WUS, and ARP orthologs, the leaf in SAM-less shoot species is initiated as a SAM and differentiates into a single apical leaf, resulting in the evolution of novel shoot-leaf mixed organs in Podostemaceae.
- Genetic Framework for Flattened Leaf Blade Formation in Unifacial Leaves of Juncus prismatocarpus
Leaf blades of unifacial leaves, such as those of iris, have only the abaxial identity and become flattened by a mechanism different from that in bifacial leaves. This work shows that the unifacial leaf blade is abaxialized at the gene expression level and identifies the DROOPING LEAF gene ortholog as a candidate responsible for flattened leaf blade formation in unifacial leaves.
- Orchestration of the Floral Transition and Floral Development in Arabidopsis by the Bifunctional Transcription Factor APETALA2
This study examines how the transcription factor APETALA2 suppresses flowering by mapping direct targets of AP2 on a genome-wide scale and comparing the map to changes in gene expression. The results indicate an unexpected level of complexity in the interactions of transcription factors with one another and their targets.
- Environmental Regulation of Lateral Root Emergence in Medicago truncatula Requires the HD-Zip I Transcription Factor HB1
Medicago truncatula HB1 is an HD-Zip transcription factor involved in the adaptive developmental response of root architecture to adverse environmental stresses. HB1 reduces lateral root emergence, likely by directly repressing the expression of an auxin-responsive transcription factor from the LBD family, LBD1.
- Natural Variation of Transcriptional Auxin Response Networks in Arabidopsis thaliana
In this study, physiological, comparative transcriptomic, and network analysis approaches identify extensive natural variation of auxin responses among A. thaliana accessions. Expression level variation in auxin signaling genes is hypothesized to contribute to downstream variation in large auxin-regulated gene clusters.
- Evidence for Light Wavelength-Specific Photoelectrophysiological Signaling and Memory of Excess Light Episodes in Arabidopsis
This work examines light wavelength–specific electrophysiological signaling and cellular light memory in Arabidopsis. Animals have their network of neurons, synapses, electrophysiological circuits and memory, but plants have their network of chloroplasts (connected by stromules), photoelectrophysiological signals transduced by bundle sheath cells, and cellular light memory.
- The bHLH Transcription Factor POPEYE Regulates Response to Iron Deficiency in Arabidopsis Roots
Iron deficiency induces a range of physiological responses that are controlled by transcriptional alterations concentrated in the root pericycle. The transcriptional regulator POPEYE regulates many of these responses possibly through interaction with iron deficiency response protein ILR3 and the putative E3 ligase protein BRUTUS.
- Arabidopsis PCR2 Is a Zinc Exporter Involved in Both Zinc Extrusion and Long-Distance Zinc Transport
This work shows that PCR2 is a membrane protein implicated in two processes, namely, the detoxification of zinc in the presence of high concentrations of zinc and the transfer of zinc from the root to the shoot. This dual role is likely made possible by PCR2’s expression pattern that differs in different parts of the root.
- Crossovers Get a Boost in Brassica Allotriploid and Allotetraploid Hybrids
There is a great demand to increase meiotic crossovers frequency in order to boost genetic diversity in traditional breeding and genetic studies. This work shows that this can be achieved by manipulating karyotype composition (diploid vs. allotriploid vs. allotetraploid) of plant hybrids.
- Repeated Polyploidy Drove Different Levels of Crossover Suppression between Homoeologous Chromosomes in Brassica napus Allohaploids
This work examines the diversity of meiotic behavior in Brassica napus allohaploids and shows that it is related to the multiple origins of this species. The results also reflect the prevalence of a major locus determining different levels of crossover suppression at the species level.
- Fast Diploidization in Close Mesopolyploid Relatives of Arabidopsis
The genome evolution of land plants is characterized by multiple waves of whole-genome duplications (WGDs). This cytogenetic and molecular phylogenetic analysis revealed an unexpected WGD event in the ancestry of Australian crucifer species with diploid-like chromosome complements.
- The CURLY LEAF Interacting Protein BLISTER Controls Expression of Polycomb-Group Target Genes and Cellular Differentiation of Arabidopsis thaliana
Pc-G proteins are key regulators of plant cell fate and development. This study examines the Pc-G interacting protein BLISTER, which has Pc-G related and unrelated functions and might link Pc-G proteins to specific developmental processes.
- Regulation of Cell Proliferation in the Stomatal Lineage by the Arabidopsis MYB FOUR LIPS via Direct Targeting of Core Cell Cycle Genes
The MYB protein FOUR LIPS (FLP) promotes Arabidopsis stomatal patterning by suppressing cell division before differentiation. FLP direct targets were found to be enriched in cell cycle genes that function in both S-G1 and G2-M phase, indicating that this transcription factor acts as a developmental integrator.
- Temporal Control of Trichome Distribution by MicroRNA156-Targeted SPL Genes in Arabidopsis thaliana
The microRNA156-targeted SQUAMOSA PROMOTER BINDING PROTEIN LIKE genes, which were reported to define an endogenous phase transition pathway, temporally control the trichome distribution on the stem and inflorescences by activating the trichome negative regulator genes TRICHOMELESS1 and TRIPTYCHON.
- DNA Replication Factor C1 Mediates Genomic Stability and Transcriptional Gene Silencing in Arabidopsis
This work describes the identification of DNA replication factor C1 in regulating genomic integrity and transcriptional gene silencing in Arabidopsis. It provides further evidence supporting the importance of core DNA replication proteins in mediating genome stability, telomere maintenance, epigenetic regulation, DNA repair, and replication.
- Arabidopsis Cockayne Syndrome A-Like Proteins 1A and 1B Form a Complex with CULLIN4 and Damage DNA Binding Protein 1A and Regulate the Response to UV Irradiation
This study shows that Arabidopsis CSAat1A, which encodes a Cockayne Syndrome A-like protein, and its homolog, CSAat1B, form a heterotetramer in response to DNA damage and thereby play a key role in the plant’s response to UV-B irradiation.
- Arabidopsis PHYTOCHROME INTERACTING FACTOR Proteins Promote Phytochrome B Polyubiquitination by COP1 E3 Ligase in the Nucleus
This work identifies COP1 as the ubiquitin E3 ligase for not only phytochrome B but also other members of the stable phytochrome family and shows that PIF transcription factors enhance phyB ubiquitination by COP1 in vitro. It provides a molecular mechanism for the termination of red light signal transduction.
- Ethylene-Induced Stabilization of ETHYLENE INSENSITIVE3 and EIN3-LIKE1 Is Mediated by Proteasomal Degradation of EIN3 Binding F-Box 1 and 2 That Requires EIN2 in Arabidopsis
The recently controversial ethylene signaling pathway has been reexamined in this study with results supporting a linear signaling pathway, in which EIN2 and EBF1/EBF2, but not MAP KINASE KINASE9, are essential signaling components required for ethylene-induced EIN3 and EIL1 protein stabilization.
- The Levels of Male Gametic Mitochondrial DNA Are Highly Regulated in Angiosperms with Regard to Mitochondrial Inheritance
This work uses technical advances to quantify the mitochondrial DNA in single cells and provides evidence that the male gamete, rather than the female gamete, plays the most critical role in regulating maternal inheritance of mitochondria in angiosperms.
- Spatial Uncoupling of Mitosis and Cytokinesis during Appressorium-Mediated Plant Infection by the Rice Blast Fungus Magnaporthe oryzae
This study examines the relationship between nuclear division and cytokinesis during formation of appressoria by a plant pathogenic fungus. It also identifies a key spatial regulator of cytokinesis and nuclear division and shows that it is required for the fungus to cause disease.
- Entry Mode–Dependent Function of an Indole Glucosinolate Pathway in Arabidopsis for Nonhost Resistance against Anthracnose Pathogens
This work describes a previously undiscovered cellular process that fungi use for entry into leaves: hyphal tip-based entry (HTE) that is independent of appressorium formation. It shows that HTE is the predominant morphogenetic response of Colletotrichum during pathogenesis at wound sites and might have broader significance as infection strategy on fruits during ripening.
- Activation of an Arabidopsis Resistance Protein Is Specified by the in Planta Association of Its Leucine-Rich Repeat Domain with the Cognate Oomycete Effector
The Arabidopsis disease resistance protein RPP1 recognizes the ATR1 effector protein from Hyaloperonospora arabidopsidis. This works shows that the molecular basis of recognition is mediated by the in planta association of the LRR domain of the RPP1 protein with the ATR1 effector protein. The in planta association of specific alleles of ATR1 leads to the activation of plant immune responses.
- A Nitrogen Response Pathway Regulates Virulence Functions in Fusarium oxysporum via the Protein Kinase TOR and the bZIP Protein MeaB
Nitrogen limitation has been proposed to act as a signal for infectious development in plant pathogens. Here, the authors show that the preferred nitrogen source ammonium represses a set of virulence-related functions in the vascular wilt fungus Fusarium oxysporum. They also identify two key elements of the nitrogen response pathway: the conserved protein kinase TOR and the bZIP factor MeaB.
- The Myosin Motor Domain of Fungal Chitin Synthase V Is Dispensable for Vesicle Motility but Required for Virulence of the Maize Pathogen Ustilago maydis
Invasion of plant cells by Ustilago maydis requires cell wall–forming enzymes, such as Mcs1, which has of a chitin synthase fused to a myosin motor head. Surprisingly, this motor head does not deliver the enzyme to the hyphal tip but is required for exocytosis of the chitin synthase. This underlies fungal wall remodeling during infection, which is necessary to avoid activation of plant defenses.
- The Tig1 Histone Deacetylase Complex Regulates Infectious Growth in the Rice Blast Fungus Magnaporthe oryzae
This study analyzed a transducin β-like gene (TIG1) from the fungal rice pathogen Magnaporthe oryzae. TIG1 was found to interact with several conserved core proteins to form a histone deacetylase complex, which is critical for invasive growth and conidiogenesis in the rice blast fungus.
- NENA, a Lotus japonicus Homolog of Sec13, Is Required for Rhizodermal Infection by Arbuscular Mycorrhiza Fungi and Rhizobia but Dispensable for Cortical Endosymbiotic Development
NENA was identified by a genetic screen for Lotus japonicus mutants impaired in arbuscular mycorrhiza and encodes a scaffold nucleoporin. nena mutants are also impaired in rhizobial root hair infection but crack entry leading to fully infected root nodules can overcome the rhizodermal nonresponsiveness of nena-1 to Nod factor.
