We start with a trio of papers that explore plant cell proliferation
Featured Review: Plants grow with a little help from their organelle friends ($)
Mitochondria and chloroplasts are semi-autonomous organelles that provide cells with energy, metabolites and hormones. Van Dingenen et al. review organelles’ dynamic roles during organ growth. As an obvious example, many chloroplast-localized proteins increase in abundance in leaf cells during the transition from non-photosynthetic sinks to photosynthetic sources. There are other less intuitive patterns of differential gene expression. Many organelle-protein encoding genes decrease in expression level as cells transition from proliferation to expansion, pointing to organelles’ critical roles as providers of energy, a role that is also supported by the analysis of loss-of-function mutants of many organelle-specific genes. J. Exp. Bot. 10.1093/jxb/erw399 Tags: Bioenergetics, Cell Biology, Genomics, Growth Regulation
Control of cell proliferation by miRNAs ($)
The interplay between transcription factors and microRNAs (miRNAs) that fine-tune transcription factor functions has emerged as a key theme in plant development. Rodriguez et al. review the functions of several miRNA families in regulating development in shoots, roots and flowers, and explore the potential for manipulating crops for increased yields through changes in miRNA activities. Curr. Opin. Plant Biol. 10.1016/j.pbi.2016.10.003. Tags: Development, Gene Regulation, Genomics, Growth Regulation
Wound healing and regeneration ($)
Wounds are healed by the stimulation of proliferation of the cells surrounding the wound. Plants are notable for their regenerative capacity, as evidenced by the initiation of roots by shoot cuttings , or callus tissue by leaf explants. Heyman et al. show that a pair of transcription factors, ERF115 and PAT1, contributes to the tissue-damage regeneration response. Nature Plants 10.1038/nplants.2016.165 Tags: Development, Gene Regulation, Genetics, Growth Regulation, Molecular Biology
Featured Review: Light effects on nuclear architecture
Light has profound effects on plants. The emergence of a seedling into light promotes de-etiolation, including cotyledon expansion, hypocotyl elongation inhibition, and photosynthesis initiation. Thousands of genes are responsive to light, which is perceived by five families of photoreceptors. Perrella and Kaiserli review recent evidence for light-mediated changes in nuclear architecture and chromatin dynamics, and how these nuclear responses contribute to changes in gene expression. New Phytol 10.1111/nph.14269 Tags: Cell Biology, Development, Gene Regulation, Genomics, Molecular Biology, Signals and Responses
Featured Review: Companion cells: a diamond in the rough ($)
Companion cells sit adjacent to sieve elements as part of the phloem system that carries sugars, nutrients and signals throughout the plant. Because sieve elements lose many of their organelles as part of their differentiation process, companion cells serve as nurse cells to support them. Otero and Helariutta review the developmental origins, transcriptomes and functions of companion cells, including their contributions to the regulation of flowering time by expression of the flowering stimulus FT. J. Exp. Bot. 10.1093/jxb/erw392 Tags: Cell Biology, Development, Genomics, Transport
Featured Review: B vitamin deficiency and abiotic stress
“Plants need their vitamins too” observe Hanson et al., who go on to note that although the importance of vitamin C (ascorbic acid) is well recognized in abiotic stress responses, the roles of B vitamins (including thiamine, biotin, niacin and others), are not as widely recognized. This paper reviews recent and classic research on B vitamin functions of in plants, and discusses how stress can affect these labile cofactors and lead to vitamin deficiencies. Plant Physiol. 10.1104/pp.16.01371 Tags: Abiotic interactions, Biochemistry, Metabolism, Physiology
Featured Review: Plant Developmental Responses to Climate Change
A distinguishing feature of plant development is its extreme plasticity; genetically identical plants look very different when grown in different conditions. Gray and Brady review the impacts of climate change, particularly elevated CO2, drought and heat, on all aspects of plant development (leaf, root, reproductive structures). They point out that our understanding is limited by patchy data availability, and that more studies need to be carried out that combine multiple climate change elements simultaneously in realistic field conditions. Devel. Cell 10.1016/j.ydbio.2016.07.023 (The current issue of Devel. Cell is dedicated to Sharon Gray). Tags: Abiotic Interactions, Development, Ecophysiology, Growth Regulation, Physiology
Noncanonical auxin signaling through ETTIN
The canonical model for auxin response is that auxin binding stabilizes the interaction between TIR1 (or related F-box proteins) and Aux/IAA repressor proteins, freeing up ARF activator proteins to switch on auxin responsive genes. Simonini et al. show that ARF3 (also known as ETTIN), which lacks the conserved PB1 domain required for Aux/IAA interactions, interacts in an auxin-sensitive manner with a different protein, IND. The authors propose that different ETTIN-TF complexes will generate different transcriptomes depending on auxin levels. Genes Devel. 10.1101/gad.285361.116 Tags: Development, Gene Regulation, Signals and Responses
Transcription factor hierarchy of stress response ($)
The hormone ABA enables plants to survive periods of water limitation through its regulation of thousands of genes. Several ABA-responsive transcription factors have been identified, but a comprehensive map of all ABA responses has been lacking. Song et al. have comprehensively examined the transcriptional responses to ABA and the interactions between ABA-responsive transcription factor and their target sequences, generating an extensive, hiearchical stress-response map. Take-home messages include the identification of new ABA-responsive transcription factors and the conclusion that dynamic interactions between TFs and targets may be more functionally relevant than stable ones. Science 10.1126/science.aag1550 Tags: Abiotic Interactions, Computational Biology, Gene Regulation, Genomics, Signals and Responses, Systems Biology
Stem piped-light activates phyB responses in the roots ($)
Root development is regulated by light signals perceived by the shoots, but how light activates responses in the roots is thought to be by transfer of signaling molecules from shoot to root. Lee et al. show that in Arabidopsis plants, light directly influences the root system while being conducted through the stem to the root where phytochrome B (phyB) is activated, in turn inducing the expression of ELONGATED HYPOCOTYL 5 (HY5). This starts a signaling pathway that induces root growth in response to light. In this way, roots respond to the aboveground light environment, even though they are not directly irradiated. Science Signaling 10.1126/scisignal.aaf6530 (Summary by Gabriela Auge) Tags: Gene Regulation, Growth Regulation, Signals and Responses
An actin mutation affects corolla tube width and pollinator visits ($)
We know that pollinators show real preferences in the flowers they visit, but the genetic basis for shifts in flower traits and their effects on pollinator interactions is sometimes unclear. Ding et al. identify a semi-dominant mutation in the monkeyflower Mimulus lewisii that leads to a fused corolla that is narrower that in wild-type flowers, and that decreases the bumblebee visitation rate. The mutation maps to an actin gene and causes a single amino acid substitution, demonstrating that small variations in ordinary genes can have big ecological effects. New Phytol. 10.1111/nph.14281 Tags: Biotic Interactions, Cell Biology, Evolution
Mitochondrial mechanosensitive ion channel ($)
The inner mitochondrial membrane has a crucial function as a selectively permeable barrier that allows a charge gradient to form for ATP production, but few inner-membrane proteins have been identified. Lee et al. screened genes encoding proteins with a mitochondrial-targeting peptide sequence and putative membrane-spanning domains. One of the genes they identified, MSL1, encodes a mitochondrial inner-membrane stretch-activated ion channel. Loss-of MSL1 function leads to an increases transmembrane potential, suggesting MSL1 is involved in the dissipation of excess membrane potential. Plant J. 10.1111/tpj.13301 Tags: Bioenergetics, Cell Biology, Transport
Correlations among Traits drives the Drought Tolerance Mechanism ($)
It is now evident that the plant drought tolerance is a function of multiple drought tolerant traits including stomatal closure, wilting, declines in hydraulic conductivity in the leaves, stems, and roots, and plant mortality. Bartlett et al. evaluated the inter-relationships amongst these traits within plants and across species. The authors found significant correlations amongst drought tolerance traits across diverse plant species and established that the functional coordination and concerted convergence is due to drought tolerance trait correlations. (Summary by Sridhar Gutam) Proc. Natl. Acad. Sci. USA. 10.1073/pnas.1604088113 Tags: Abiotic Interactions, Botany, Ecophysiology, Physiology, Transport
Extrapolation of lab results to natural environments
Researchers often try to translate the results of plants grown in controlled conditions (growth chambers and glasshouses) to responses in natural conditions (field), but few make the real lab vs field comparison by repeating experiments in both settings. In this review, Poorter et al. searched through the literature to analyze how much lab data can be extrapolated to field conditions and predict plant behavior in natural conditions. They analyzed several responses, from plant size to yield, to different environmental cues (temperature, plant density, day length, etc.) and they ranked those responses for different species or genotypes in lab vs field experiments. The authors finished the review with some insights on how to manage and design lab experiments to be able to make meaningful predictions of plant behavior in natural conditions. New Phytol. 10.1111/nph.14243 (Summary by Gabriela Auge) Tags: Abiotic Interactions, Ecophysiology, Growth Regulation, Physiology
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