Climate-tracking species are not invasive
Applying an invasive framework to native species that are shifting their ranges in response to climate change adopts an adversarial, local and static paradigm that is often at odds with protecting global biodiversity.
Nature Climate Change
Multiple origins of dichotomous and lateral branching during root evolution
Hetherington et al.report that many euphyllophytes that were extant during the Devonian and Carboniferous periods developed dichotomous roots. Their data indicate that dichotomous root branching evolved in both lycophytes and euphyllophytes. Lateral roots then evolved at different times in three major lineages of extant euphyllophytes—the lignophytes, ferns and horsetails. The multiple origins of dichotomous and lateral root branching are extreme cases of convergent evolution that occurred during the Devonian and Carboniferous periods when the land-plant flora underwent a radiation in morphological diversity.
The maleness of larger angiosperm flowers
Paterno et al. show that heavier hermaphrodite flowers tend to be male-biased and invest strongly in petals to export their pollen, while lighter flowers tend to be female-biased and invest more in sepals to ensure the success of their own ovules. Strong male–male competition, represented by the ecological contest among pollen donors, helps to explain why flower biomass varies several orders of magnitude across the angiosperms and many aspects of their pollination biology.
Mutually opposing activity of PIN7 splicing isoforms is required for auxin-mediated tropic responses in Arabidopsis thaliana
Kashkan et al. reveal, in the plant model Arabidopsis thaliana, that the PIN7 gene, which encodes a polarly localized transporter for the phytohormone auxin, produces two evolutionarily conserved transcripts. These isoforms PIN7a and PIN7b, differing in a 4 amino acid motif, are present at nearly equal levels in most cells, except some early developing tissues where the expression of PIN7b is moderately prevalent. Both proteins also transport auxin with similar capacity and directionality. However, only PIN7a but not PIN7b cDNA rescues the phenotypes associated with the pin7 knock-out mutation, consistent with their differences in the subcellular trafficking and dynamics at the plasma membrane.
Chromatin Regulates Bipartite-Classified Small RNA Expression to Maintain Epigenome Homeostasis in Arabidopsis
Eukaryotic genomes are partitioned into euchromatic and heterochromatic domains to regulate gene expression and other fundamental cellular processes. However, chromatin is dynamic during growth and development, and must be properly re-established after its decondensation. Small interfering RNAs (siRNAs) promote heterochromatin formation in eukaryotes, but little is known about how chromatin regulates siRNA transcription. Papareddy et al. demonstrated that thousands of transposable elements (TEs) produce exceptionally high levels of siRNAs in Arabidopsis thaliana embryos. Depending on whether they are located in euchromatic or heterochromatic regions of the genome, bipartite-classified TEs generate siRNAs throughout embryogenesis according to two distinct patterns. siRNAs are transcribed in embryos and required to direct the re-establishment of DNA methylation on TEs from which they are derived in the new generation.
Freezing and water availability structure the evolutionary diversity of trees across the Americas
Segovia et al. find a fundamental divide in tree lineage composition between tropical and extratropical environments, defined by the absence versus presence of freezing temperatures. Within the Neotropics, they uncover a further evolutionary split between moist and dry forests. Their results demonstrate that American tree lineages tend to retain their ancestral environmental relationships and that phylogenetic niche conservatism is the primary force structuring the distribution of tree biodiversity. Their study establishes the pervasive importance of niche conservatism to community assembly even at intercontinental scales.
Sex‐chrom, a database on plant sex chromosomes
Baránková et al. present Sex‐chrom: a database on plant sex chromosomes (www.sexchrom.csic.es), which aims to provide an easily accessible and organized information source for scientists and a general audience interested in this field. Basic data such as complete taxonomic classification of the species, chromosome number, genome size (2C), ploidy level, sex determination mechanism, presence of homomorphic or heteromorphic sex chromosomes and their corresponding sources are easily available for 178 species of 84 genera and 65 families. Besides, the database contains specific sections for ten selected model systems in plant sex chromosome research such as Silene latifolia and Rumex acetosa.
No evidence for transient transformation via pollen magnetofection in several monocot species
The development of rapid and efficient transformation methods for many plant species remains an obstacle in both the basic and applied plant sciences. A novel method described by Zhao et al. (2017) used magnetic nanoparticles to deliver DNA into pollen grains of several dicot species, and one monocot (lily), to achieve transformation (“pollen magnetofection”). Using the published protocol, extensive trials by two independent research groups showed no indication of transient transformation success with pollen from two monocots, maize and sorghum. To further address the feasibility of magnetofection, lily pollen was used for side-by-side trials of magnetofection with a proven methodology for transient transformation, biolistics. Using a Green Fluorescent Protein reporter plasmid, transformation efficiency with the biolistic approach averaged 0.7% over three trials. However, the same plasmid produced no recognizable transformants via magnetofection, despite screening >3500 individual pollen grains. Vejlupkova et al. conclude that pollen magnetofection is not effective for transient transformation of pollen for at least three species of monocots, and suggest that efforts to replicate the magnetofection protocol in dicot species would be useful to fully assess its potential.
Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin co-receptor assemblies
Cullin RING-type E3 ubiquitin ligases SCFTIR1/AFB1-5 and their AUX/IAA targets perceive the phytohormone auxin. The F-box protein TIR1 binds a surface-exposed degron in AUX/IAAs promoting their ubiquitylation and rapid auxin-regulated proteasomal degradation. By adopting biochemical, structural proteomics and in vivo approaches Niemeyer et al. unveil how flexibility in AUX/IAAs and regions in TIR1 affect their conformational ensemble allowing surface accessibility of degrons.
Light-powered CO2 fixation in a chloroplast mimic with natural and synthetic parts
Plant chloroplasts enclose two major photosynthetic processes: light reactions, which generate the energy carriers adenosine triphosphate and reduced nicotinamide dinucleotide phosphate (NADPH), and dark reactions, which use these molecules to fix carbon dioxide and build biomass. Miller et al. appropriated natural components, thylakoid membranes from spinach, for the light reactions and showed that these could be coupled to a synthetic enzymatic cycle that fixes carbon dioxide within water-in-oil droplets.
Landscape epidemiology of ash dieback
Grosdidier et al. showed that the landscape characteristics strongly affect the development and spread of ash dieback. The disease is far less severe in forest conditions when ash density is low or in open canopies such as hedges and isolated trees. Ash trees are often in these types of landscapes, which should strongly limit the overall impact of ash dieback.
Journal of Ecology