SciCombinator

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Concept: Vascular tissue

271

Electronic plants, e-Plants, are an organic bioelectronic platform that allows electronic interfacing with plants. Recently we have demonstrated plants with augmented electronic functionality. Using the vascular system and organs of a plant, we manufactured organic electronic devices and circuits in vivo, leveraging the internal structure and physiology of the plant as the template, and an integral part of the devices. However, this electronic functionality was only achieved in localized regions, whereas new electronic materials that could be distributed to every part of the plant would provide versatility in device and circuit fabrication and create possibilities for new device concepts. Here we report the synthesis of such a conjugated oligomer that can be distributed and form longer oligomers and polymer in every part of the xylem vascular tissue of a Rosa floribunda cutting, forming long-range conducting wires. The plant’s structure acts as a physical template, whereas the plant’s biochemical response mechanism acts as the catalyst for polymerization. In addition, the oligomer can cross through the veins and enter the apoplastic space in the leaves. Finally, using the plant’s natural architecture we manufacture supercapacitors along the stem. Our results are preludes to autonomous energy systems integrated within plants and distribute interconnected sensor-actuator systems for plant control and optimization.

Concepts: Protein, Blood, Integrated circuit, Monomer, Transistor, Vascular plant, Fern, Vascular tissue

42

CRISPR/Cas9 technology is a versatile tool for targeted mutagenesis in many organisms, including plants. However, this technique has not been applied to the Japanese morning glory (Ipomoea [Pharbitis] nil), a traditional garden plant chosen for the National BioResource Project in Japan. We selected dihydroflavonol-4-reductase-B (DFR-B) of I. nil, encoding an anthocyanin biosynthesis enzyme, as the target gene, and changes in the stem colour were observed during the early stages of plant tissue culture by Rhizobium [Agrobacterium]-mediated transformation. Twenty-four of the 32 (75%) transgenic plants bore anthocyanin-less white flowers with bi-allelic mutations at the Cas9 cleavage site in DFR-B, exhibiting a single base insertion or deletions of more than two bases. Thus, these results demonstrate that CRISPR/Cas9 technology enables the exploration of gene functions in this model horticultural plant. To our knowledge, this report is the first concerning flower colour changes in higher plants using CRISPR/Cas9 technology.

Concepts: Genetics, Mutation, Organism, Plant, Vascular plant, Flowering plant, Vascular tissue, Ipomoea

34

Eucalyptus trees may translocate Au from mineral deposits and support the use of vegetation (biogeochemical) sampling in mineral exploration, particularly where thick sediments dominate. However, biogeochemistry has not been routinely adopted partly because biotic mechanisms of Au migration are poorly understood. For example, although Au has been previously measured in plant samples, there has been doubt as to whether it was truly absorbed rather than merely adsorbed on the plant surface as aeolian contamination. Here we show the first evidence of particulate Au within natural specimens of living biological tissue (not from laboratory experimentation). This observation conclusively demonstrates active biogeochemical adsorption of Au and provides insight into its behaviour in natural samples. The confirmation of biogeochemical adsorption of Au, and of a link with abiotic processes, promotes confidence in an emerging technique that may lead to future exploration success and maintain continuity of supply.

Concepts: Histology, Eucalyptus, Mineral, Tissue, Geology, Environmental science, Vascular tissue, Ore

28

The butanol-HCl spectrophotometric assay is widely used for quantifying extractable and insoluble condensed tannins (CT, syn. proanthocyanidins) in foods, feeds, and foliage of herbaceous and woody plants, but the method underestimates total CT content when applied directly to plant material. To improve CT quantitation, we tested various cosolvents with butanol-HCl and found that acetone increased anthocyanidin yields from two forage Lotus species having contrasting procyanidin and prodelphinidin compositions. A butanol-HCl-iron assay run with 50% (v/v) acetone gave linear responses with Lotus CT standards and increased estimates of total CT in Lotus herbage and leaves by up to 3.2-fold over the conventional method run without acetone. The use of thiolysis to determine the purity of CT standards further improved quantitation. Gel-state 13C and 1H-13C HSQC NMR spectra of insoluble residues collected after butanol-HCl assays revealed that acetone increased anthocyanidin yields by facilitating complete solubilization of CT from tissue.

Concepts: Plant, Fern, Leaf, Enzyme assay, Tannin, Proanthocyanidin, Oak, Vascular tissue

28

The xylem and phloem, major conducting and supporting tissues in vascular plants, are established by cell division and cell-type specification in the procambium/cambium. The organization of the xylem, phloem, and procambium/cambium is tightly controlled. However, the underlying regulatory mechanisms remain largely unknown. In this study, we report the discovery of two transcription factors, AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN 3 (AHL3) and AHL4, which regulate vascular tissue boundaries in Arabidopsis thaliana roots. In either of the knockout mutants of AHL3 and AHL4, encoding closely related AT-hook transcription factors, a misspecification of tissue boundaries between the xylem and procambium occurred and ectopic xylem developed in the procambium domain. In plants, specific types of transcription factors can serve as direct intercellular signals by moving from one cell to another, playing crucial roles in tissue patterning. Adding to this paradigm, AHL4 moves actively from the procambium to xylem in the root meristem to regulate the tissue boundaries. When the intercellular movement of AHL4 was impaired, AHL4 could not complement the xylem phenotype in the ahl4. Furthermore, AHL4 revealed unique characteristics in that it interacts with AHL3 in vivo and that this interaction facilitates their intercellular trafficking. Taken together, this study uncovered a novel mechanism in vascular tissue patterning that requires the intercellular trafficking of two interacting transcription factors.

Concepts: Plant, Tissues, Vascular plant, Root, Xylem, Phloem, Meristem, Vascular tissue

28

• Premise of the study: How leaf shape is regulated is a long-standing question in botany. For diverse groups of dicotyledon species, lamina folding along the veins and geometry of the space available for the primordia can explain the palmate leaf morphology. Dubbed the kirigami theory, this hypothesis of fold-dependent leaf shape regulation has remained largely theoretical. Using Acer pseudoplatanus, we investigated the mechanisms behind the two key processes of kirigami leaf development. • Methods: Cytological examination and quantitative analyses were used to examine the course of the vein-dependent lamina folding. Surgical ablation and tissue culturing were employed to test the effects of physical constraints on primordia growth. The final morphology of leaves growing without steric constraints were predicted mathematically. • Key results: The cytological examination showed that the lamina’s abaxial side along the veins grows substantially more than the adaxial side. The abaxial hypergrowth along the veins and the lamina extension correlated with the lamina folding. When a primordium was released from the physical constraints imposed by the other primordia, it rapidly grew into the newly available space, while maintaining the curvature inward. The morphology of such a leaf was predicted to lack symmetry in the lobe shapes. • Conclusions: The enhanced growth on the abaxial side of the lamina along the veins is likely to drive lamina folding. The surgical ablation provided clear support for the space-filling nature of leaf growth; thus, steric constraints play a role in determination of the shapes of folded leaves and probably also of the final leaf morphology.

Concepts: Photosynthesis, Scientific method, Plant physiology, Fern, Leaf, Plant morphology, Maple, Vascular tissue

28

Vascular formation is intimately associated with bone formation during distraction osteogenesis (DO). While prior studies on this association have focused on vascular formation locally within the regenerate, we hypothesized that this vascular formation, as well as the resulting osteogenesis, relies heavily on the response of the vascular network in surrounding muscular compartments. To test this hypothesis, the spatiotemporal sequence of vascular formation was assessed in both muscular and osseous compartments in a murine model of DO and was compared to the progression of osteogenesis. Micro-computed tomography (μCT) scans were performed sequentially, before and after demineralization, on specimens containing contrast-enhanced vascular casts. Image registration and subtraction procedures were developed to examine the co-related, spatiotemporal patterns of vascular and osseous tissue formation. Immunohistochemistry was used to assess the contributory roles of arteriogenesis (formation of large vessels) and angiogenesis (formation of small vessels) to overall vessel formation. Mean vessel thickness showed an increasing trend during the period of active distraction (p=0.068), whereas vessel volume showed maximal increases during the consolidation period (p=0.009). The volume of mineralized tissue in the regenerate increased over time (p<0.039), was correlated with vessel volume (r=0.59; p=0.025), and occurred primarily during consolidation. Immunohistological data suggested that: 1) the period of active distraction was characterized primarily by arteriogenesis in the surrounding muscle; 2) during consolidation, angiogenesis predominated in the intraosteal region; and 3) vessel formation proceeded from the surrounding muscle into the regenerate. These data show that formation of vascular tissue occurs in both muscular and osseous compartments during DO and that periods of intense osteogenesis are concurrent with those of angiogenesis. The results further suggest the presence of morphogenetic factors that coordinate the development of vascular tissues from the intramuscular compartment into the regions of osseous regeneration.

Concepts: Bone, Skeletal system, Tissues, Sequence, Tissue, Vascular plant, Vascular tissue

9

Accumulation of Aluminium (Al) at concentrations far above 1,000 mg kg-1 in aboveground plant tissues of Arbor aluminosa (Symplocos) species is the main reason why traditional Indonesian weavers rely on their leaves and bark as a mordant for dyeing textile. Recently, Symplocos species have become a flagship species for the conservation efforts of weaving communities due to their traditionally non-sustainable sampling and increasing demand for Symplocos plant material. Here we investigated Symplocos odoratissima, S. ophirensis and S. ambangensis at three montane rainforest sites in Central Sulawesi to measure Al levels in different tissues and organs. The highest Al concentrations were found in old leaves (24,180 ± 7,236 mg·kg-1 dry weight, mean ± SD), while young leaves had significantly lower Al levels (20,708 ± 7,025 mg·kg-1). Al accumulation was also lower in bark and wood tissue of the trunk (17,231 ± 8,356 mg·kg-1 and 5,181 ± 2,032 mg·kg-1, respectively). Two Al excluding species (Syzigium sp. and Lithocarpus sp.) contained only high Al levels in their roots. Moreover, no difference was found in soil pH (4.7 ± 0.61) and nutrient (K, Ca, Fe, Mg) availability at different soil levels and within or outside the crown of Symplocos trees, except for the upper soil layer. Furthermore, a positive and significant correlation between Al and Ca concentrations was found at the whole plant level for Symplocos, and at the leaf level for S. ophirensis and S. ambangensis, suggesting a potential role of Ca in Al uptake and/or detoxification within the plant. Our results provide evidence for strong Al accumulation in Symplocos species and illustrate that both Al accumulation and exclusion represent two co-occurring strategies of montane rainforest plants for dealing with Al toxicity. Indonesian weavers should be encouraged to harvest old leaves, which have the most efficient mordant capacity due to high Al concentrations.

Concepts: Iron, Plant, Aluminium, Tree, Fern, Leaf, Oak, Vascular tissue

4

Vascular tissue, comprising xylem and phloem, is responsible for the transport of water and nutrients throughout the plant body. Such tissue is continually produced from stable populations of stem cells, specifically the procambium during primary growth and the cambium during secondary growth. As the majority of plant biomass is produced by the cambium, there is an obvious demand for an understanding of the genetic mechanisms that control the rate of vascular cell division. Moreover, wood is an industrially important product of the cambium, and research is beginning to uncover similar mechanisms in trees such as poplar. This review focuses upon recent work that has identified the major molecular pathways that regulate procambial and cambial activity.

Concepts: Tissues, Vascular plant, Plant physiology, Plant anatomy, Plant stem, Xylem, Vascular tissue, Vascular cambium

2

Water storage is thought to play an integral role in the maintenance of whole plant water balance. The contribution of both living and dead cells to water storage can be derived from rehydration and pressure-volume curves on excised plant material, but the underlying tissue-specific emptying/refilling dynamics remain unclear. Here, we used X-ray computed micro-tomography (microCT) to characterize refilling of xylem fibers, pith cells and vessels under both excised and in-vivo conditions in Laurus nobilis. In excised stems supplied with H2O, water uptake exhibited a biphasic response curve, and microCT images showed that high water storage capacitance was associated with fiber and pith refilling as driven by capillary forces; fibers refilled more rapidly than pith cells while vessel refilling was minimal. In excised stems that were sealed, fiber and pith refilling was associated with vessel emptying, indicating a link between tissue connectivity and water storage. In contrast, refilling of fibers, pith cells and vessels was negligible in intact saplings over two timescales, a period of 24-h and 3-weeks. However, those compartments did refill slowly when the shoot was covered to prevent transpiration. Collectively, our data i) provide direct evidence that storage compartments for capillary water refill in excised stems but rarely under in-vivo conditions, ii) highlight that estimates of capacitance from excised samples should be interpreted with caution as certain storage compartments may not be utilized in the intact plant, and iii) question the paradigm that fibers play a substantial role in daily discharge/recharge of stem capacitance in an intact tree.

Concepts: Water, Blood vessel, Tree, Vascular plant, Plant physiology, Plant stem, Xylem, Vascular tissue