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Cork is a natural cellular material of biological origin with a combination of properties that make it suited for worldwide use as a wine sealant and insulation material. Cork has low density, is buoyant, is not very permeable to fluids, has a low thermal coefficient, exhibits elasticity and deformation without fracturing under compression, and has considerable durability. Such characteristics result from the features of its cellular structure, primarily its cell dimensions and topology, and from the chemical composition of the cell wall. The characteristics of the two main chemical components (suberin and lignin, which represent 53% and 26%, respectively, of the cell wall) have been analyzed. The limits of natural variation and their impacts on cork properties are discussed and used to define the material as “cork”.

Fusaric acid (=FA) is a phytotoxin produced by Fusarium oxysporum, pathogen of wilt disease on tomato. A concentration of FA causes death of plant. However, low concentration will elicit various plant defense responses and inhibit pathogen growth. The research focused on the observation of lignin and suberin formation after application of FA on tomato in different concentration. This research was caried out at elementary laboratory of Agriculture Faculty of Muhammadiyah University of Parepare, Parepare and Micology Laboratory of Gadjah Mada University, Yogyakarta. Four concentrations of FA (sigma) 0, 25, 50, 75, and 100 ppm were used in this research, whereas inoculation with Fusarium oxysporum was served as control. Lignin and suberin formations in plant cell as structural resitantance response were analyzied by using microtechnique protocol. The result of histological analysis showed that treatment of F. oxysporum, 10 ppm, 50 ppm, 75 ppm, and 100 ppm of FA, caused a change in lignin content of tomato cell on 10 – 40 days after application and followed also by necrotitation. The application of 25 ppm FA increases the lignin and the suberin content without necrosis on 20 and 30 days after application.

Mangrove plants demonstrate an impressive ability to tolerate environmental pollutants, but excessive levels of cadmium (Cd) can impede their growth. Few studies have focused on the effects of apoplast barriers on heavy metal tolerance in mangrove plants. To investigate the uptake and tolerance of Cd in mangrove plants, two distinct mangrove species, Avicennia marina and Rhizophora stylosa , are characterized by unique apoplast barriers. The results showed that both mangrove plants exhibited the highest concentration of Cd 2+ in roots, followed by stems and leaves. The Cd 2+ concentrations in all organs of R. stylosa consistently exhibited lower levels than those of A. marina . In addition, R. stylosa displayed a reduced concentration of apparent PTS and a smaller percentage of bypass flow when compared to A. marina . The root anatomical characteristics indicated that Cd treatment significantly enhanced endodermal suberization in both A. marina and R. stylosa roots, and R. stylosa exhibited a higher degree of suberization. The transcriptomic analysis of R. stylosa and A. marina roots under Cd stress revealed 23 candidate genes involved in suberin biosynthesis and 8 candidate genes associated with suberin regulation. This study has confirmed that suberized apoplastic barriers play a crucial role in preventing Cd from entering mangrove roots.

Premise: Leaf subepidermal secretory cavities are a notable trait in Myrtaceae, but their formation is still controversial because of the lack of consensus on their ontogeny among authors. Knowledge about the compounds present in these cavities has grown over the last few years, demonstrating that terpenoid-rich oils are not their unique content. These two points are the focus of this study on the ontogeny, structure, and contents of secretory cavities in neotropical Myrtaceae., Methods: We used histochemical tests and Raman analysis to verify the basic chemical composition of the cavity contents of nine species. We studied the ontogeny of glands in one species, comparing aldehyde-fixed tissues and fresh sections mounted in an inert medium., Results: We observed schizogenous development and appearance of the secretory cavities and found that sample processing may induce cell breakdown, which can be misinterpreted as lysigeny. The content of these cavities contains putative terpenes, resins, carbonyl groups, and flavonoids., Conclusions: Our findings support the hypothesis that the lysigenous appearance of the oil glands is a technical artifact. These tissue distortions must be considered when interpreting the development of this type of secretory structure. Moreover, the basic analyses of chemical constituents show for the first time that the glands of neotropical Myrtaceae are potential reservoirs of some compounds such as flavonoids previously reported as novelties for a few other myrtaceous species. Because some of them are non-lipid compounds, the idea that the glands are just oil repositories is no longer applicable., (© 2023 Botanical Society of America.)

Forest soil organic carbon (SOC) is one of the largest reservoirs of terrestrial carbon (C) and is a major component of the global C cycle. Yet there is still uncertainty regarding how ecosystems, and the SOC they store, will respond to changes due to anthropogenic processes. Current and future reactive nitrogen (N) deposition to forest soils may alter biogeochemical processes and shift both the quantity and quality of stored SOC. We studied SOC storage and molecular-level composition after 22 years of N additions (100 kg N ha−1 y−1) in a temperate deciduous forest. SOC storage in surface soils increased by 0.93 kg m−2 due to a decline in microbial biomass (phospholipid fatty acids) and litter decomposition. N additions resulted in the selective preservation of a range of plant-derived compounds including steroids, lignin-derived, cutin-derived, and suberin-derived compounds that have anti-microbial properties or are non-preferred microbial substrates. This overall shift in SOC composition suggests limited sustainability and a decline in soil health. The reduction in microbial biomass and increase in specific SOC components demonstrate that long-term N fertilization negatively alters fundamental C cycling in forest soils. This study also demonstrates unequivocally that anthropogenic impacts on C and N cycling in forests at the molecular-level must be considered more holistically. [ABSTRACT FROM AUTHOR]

Summary: Barley (Hordeum vulgare) is more drought tolerant than other cereals, thus making it an excellent model for the study of the chemical, transcriptomic and physiological effects of water deficit. Roots are the first organ to sense soil water deficit. Therefore, we studied the response of barley seminal roots to different water potentials induced by polyethylene glycol (PEG) 8000.We investigated changes in anatomical parameters by histochemistry and microscopy, quantitative and qualitative changes in suberin composition by analytical chemistry, transcript changes by RNA‐sequencing (RNA‐Seq), and the radial water and solute movement of roots using a root pressure probe.In response to osmotic stress, genes in the suberin biosynthesis pathway were upregulated that correlated with increased suberin amounts in the endodermis and an overall reduction in hydraulic conductivity (Lpr). In parallel, transcriptomic data indicated no or only weak effects of osmotic stress on aquaporin expression.These results indicate that osmotic stress enhances cell wall suberization and markedly reduces Lpr of the apoplastic pathway, whereas Lpr of the cell‐to‐cell pathway is not altered. Thus, the sealed apoplast markedly reduces the uncontrolled backflow of water from the root to the medium, whilst keeping constant water flow through the highly regulated cell‐to‐cell path. [ABSTRACT FROM AUTHOR]

Non-isotopic strontium (Sr) is a non-essential element found in the environment but its effect on plants is unknown. Sr amount may reach even several thousands of ppm at near roads with heavy traffic. The effect of high Sr concentration on vegetative plants has not been investigated. Here, the effect of Sr on the growth of Solanum lycopersicum was studied. The fresh weights of the shoots and roots were reduced by addition of Sr in a dosedependent manner, suggesting that a high Sr concentration is toxic to the tomato plant. The Sr concentration in the shoots and roots increased in a dose-dependent manner. The Sr concentration in the shoots was 2 to 4 fold higher than that in the roots. Shoots treated with 10 mM Sr had a higher accumulation of Mg, and Ca ions than those in the control shoots. Roots treated with 10 mM Sr only had a higher Ca accumulation than that in the control. The tomato roots were stained by Fluorol Yellow 088 to observe the formation of suberin. In the mature zone of roots, the fluorescence of suberin was increased by 10 mM Sr treatment, indicating that suberin induction caused higher Ca accumulation. [ABSTRACT FROM AUTHOR]

Background and Aims Limited supply of mineral nutrients often reduces plant growth and transpirational water flow while increasing the ratio of water-absorbing root to water-losing shoot surface. This could potentially lead to an imbalance between water uptake (too much) and water loss (too little). The aim of the present study was to test whether, as a countermeasure, the hydraulic properties (hydraulic conductivity, Lp) of roots decrease at organ and cell level and whether any decreases in Lp are accompanied by decreases in the gene expression level of aquaporins (AQPs) or increases in apoplastic barriers to radial water movement. Methods Barley plants were grown hydroponically on complete nutrient solution, containing 2 m m K+ (100 %), or on low-K solution (0.05 m m K+; 2.5 %), and analysed when they were 15–18 d old. Transpiration, fresh weight, surface area, shoot water potential (ψ), K and Ca concentrations, root (exudation) and cortex cell Lp (cell pressure probe), root anatomy (cross-sections) and AQP gene expression (qPCR) were analysed. Key Results The surface area ratio of root to shoot increased significantly in response to low K. This was accompanied by a small decrease in the rate of water loss per unit shoot surface area, but a large (~50 %) and significant decrease in Lp at root and cortex cell levels. Aquaporin gene expression in roots did not change significantly, due to some considerable batch-to-batch variation in expression response, though HvPIP2;5 expression decreased on average by almost 50 %. Apoplastic barriers in the endodermis did not increase in response to low K. Conclusions Barley plants that are exposed to low K adjust to an increased ratio of root (water uptake) to shoot (water loss) surface primarily through a decrease in root and cell Lp. Reduced gene expression of HvPIP2;5 may contribute to the decrease in Lp. [ABSTRACT FROM AUTHOR]

Silicon (Si) is an element frequently associated with remedial properties in plant defence against various biotic stressors. Application of Si in plant–fungus interactions offers an intriguing research subject for its potential to reduce fungal disease‐related losses in agriculture. However, Si‐mediated changes in the plant metabolism must be first elucidated. The present microscopic study explores the effect of Si amendment on ultrastructural, cytological and anatomical aspects of the interaction between Sorghum bicolor 'Gadambalia' primary roots and the necrotrophic fungus Alternaria alternata. Bright‐field microscopy observations revealed that Si supplementation helped sorghum seedlings to restrict the growth of A. alternata, possibly by cell wall modifications of the root exodermis, limiting further fungal invasion. Ultrastructural analyses by transmission electron microscopy showed intense vesiculation in exodermal cells of inoculated roots. Fluorescence microscopy with suberin‐ and phenolic‐specific staining indicated a significant enhancement in the deposition of these substances in exodermal cell walls upon Si supplementation. The increased accumulation of phenolics in Si‐supplied plants was also confirmed by Raman spectroscopy. In conclusion, Si amendment seemed to alleviate the negative effect of A. alternata infection in sorghum roots, which is shown by restricted distribution of fungal hyphae in root tissues probably due to Si‐mediated deposition of suberin and phenolics in the exodermis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Beaucarnea recurvata Lemaire (Ponytail palm) cork studied for the first time. • It has a low suberin content and enhanced lignocellulosic nature. • Suberin contains high amount of alkanoic acids and differs from Quercus suber Linnaeus cork. • Lignin composition shows a HGS-type of lignin. • Cellular structure is typical of corks but cells are large and thick-walled. Abstract Ponytail palm (Beaucarnea recurvata Lemaire) is a succulent plant indigenous to Mexico frequently used as an ornamental plant throughout the world. The mature trees develop a thick corky outer bark that was studied here for the first time and compared with cork of Quercus suber Linnaeus (cork oak) and other species. The anatomical structure of ponytail palm cork showed a typical honeycomb structure in the tangential section and a brick-wall layer in the transverse section. The cells were larger and had thicker cell walls than those of Q. suber cork. Ponytail palm cork had a distinct growth ring pattern but the cell wall undulation lacked the regular wave pattern as in Q. suber cork. Fiber-like cellular structures were present protuberating from the lenticular channels. Ponytail palm cork chemically differs from Q. suber and other corks by a much lower content of suberin and enhancement of the lignocellulosic nature (18.2% extractives, 11.8% suberin, 29.7% lignin and 39.0% polysaccharides). Although in general similar to that of Q. suber cork, suberin composition of ponytail palm cork has specific features namely regarding the ratio of ɑ,ω-diacids and ω-substituted hydroxyacids and presence of higher amounts of alkanoic acids. The lignin of ponytail palm cork is a HGS-type of lignin (1:12:5) with a S/G ratio of 0.4. These results add to data showing that monomeric composition of suberin and lignin of corks are species' specific. The lipophilic extractives included mainly saturated alkanoic acids and sterols while the polar extractives showed overall low amount of phenolics and unremarkable antioxidant properties. [ABSTRACT FROM AUTHOR]

With climate change, forests are expected to receive increased inputs of carbon (C) and nitrogen (N) but it is unclear how this will modify forest C cycling and storage at the molecular-level. To investigate the response of forest soil organic matter (SOM) to changes in soil inputs, a study area was established in a Michigan hardwood forest as part of the Detrital Input and Removal Treatments (DIRT) network. Experimental treatments were comprised of both exclusions of detrital inputs (No Litter, No Roots, No Inputs) and additions of C and N (Double Litter, N-Addition, Double Litter + N, Wood). After 10 years of treatment, the soils were characterized using elemental analysis, molecular biomarker techniques, nuclear magnetic resonance spectroscopy, and microbial biomass C measurements. Although manipulation of detrital inputs did not significantly change the soil C and N content after 10 years, alterations in the cycling and distribution of SOM components were observed. Root exclusion enhanced SOM degradation, while doubling litter favoured the degradation of more labile forms of soil C such as unsaturated n-alkanoic acids and simple sugars. N-Addition and Double Litter + N increased the concentrations of extractable biomarkers, including aliphatic and cyclic lipids and compounds derived from cutin, suberin, and lignin. Microbial biomass C also varied with experimental litter input manipulations and N addition, and these data were consistent with the observed changes in SOM composition. Overall, the observed shifts in SOM chemistry after 10 years of manipulating ecosystem inputs highlight the sensitivity of natural systems to changes in amounts of C and N inputs from roots and litter, and N inputs from external sources. [ABSTRACT FROM AUTHOR]

Large nitrogen, phosphorus and potassium fertilizer inputs are used in many crop systems. Identifying genetic loci controlling nutrient accumulation may be useful in crop breeding strategies to increase fertilizer use efficiency and reduce financial and environmental costs. Here, variation in leaf nitrate concentration across a diversity population of 383 genotypes of Brassica napus was characterized. Genetic loci controlling variation in leaf nitrate, phosphorus and potassium concentration were then identified through Associative Transcriptomics using single nucleotide polymorphism (SNP) markers and gene expression markers (GEMs). Leaf nitrate concentration varied over 8-fold across the diversity population. A total of 455 SNP markers were associated with leaf nitrate concentration after false-discovery-rate (FDR) correction. In linkage disequilibrium of highly associated markers are a number of known nitrate transporters and sensors, including a gene thought to mediate expression of the major nitrate transporter NRT1.1. Several genes influencing root and root-hair development co-localize with chromosomal regions associated with leaf P concentration. Orthologs of three ABC-transporters involved in suberin synthesis in roots also co-localize with association peaks for both leaf nitrate and phosphorus. Allelic variation at nearby, highly associated SNPs confers large variation in leaf nitrate and phosphorus concentration. A total of five GEMs associated with leaf K concentration after FDR correction including a GEM that corresponds to an auxin-response family protein. Candidate loci, genes and favorable alleles identified here may prove useful in marker-assisted selection strategies to improve fertilizer use efficiency in B. napus. [ABSTRACT FROM AUTHOR]

Background and Aims Heavy metals induce changes in root metabolism and physiology, which can lead to a complex remodelling of the root system. The final morphological responses of radish (Raphanus sativus) roots exposed to toxic concentrations of the heavy metal (Cu) include root growth inhibition, differentiation of xylem vessels close to the root tip, enhanced suberin lamellae deposition and enhanced lateral root production. Recently, we have found that such changes in root morphology and anatomy are coupled to the formation of a subero-lignified apical deposit (SLAD) very close to the root tip. Methods To clarify the details of the formation of a SLAD in the root tip, we conducted experiments with radish roots exposed to a high Cu concentration (60 µ m). Histochemical analysis of lignin and suberin as well as analysis of spatial–temporal characteristics of SLAD formation were performed by bright-field, fluorescence and confocal microscopy. Key Results This unique structure, not longer than 100 µm, consists of modified cell walls of the central cylinder that are encircled by a short cylinder of prematurely suberized endodermal cells. A SLAD starts to form, in both primary and lateral roots, after cessation of root elongation, and it is coupled with xylem differentiation and root branching close to the root apex. We noticed that deposition of phenolic substances into a SLAD, mainly suberin in the endodermis, is spatially separated from suberization or lignification in basally located endodermis. Conclusions Although the main reason for formation of a SLAD is elusive, we suggest that it is a part of stress-induced responses which relate to decreased root growth or permeability in heavy metal stress. [ABSTRACT FROM AUTHOR]

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The chemical composition of Douglas-fir bark was analyzed at three stem height levels of trees with different ages from two geographical locations. Cork and phloem in the bark's rhytidome were analyzed separately at stem bottom: extractives (49.8% and 17.0%, respectively), suberin (30.1% in cork) and hemicelluloses, namely arabinose content (25.3% and. 4.8% of all monomers, respectively). Suberin composition includes α,ω-alkanoic diacids (38.6%), ω-hydroxyalkanoic acids (25.6%), alkanoic acids (18.2%), alkanols (2.2%), and aromatics (8.8%). Bark's chemical composition is age-related, namely regarding suberin content: at 45, 30 and, 17 years of age, bark contained respectively 25.4%, 2.6%, and 0.9% of suberin; 24.5%, 33.9%, and 29.8% of lignin; and 29.4%, 20.6%, and 25.7% of extractives. This difference is due to the small number of periderms and low cork content in barks with 30 or less years. When aiming at a cork-targeted valorization, the lower stem parts of mature Douglas-fir trees should be considered while the high content of polar extractives at all stem heights allows an overall potential valorization. [ABSTRACT FROM AUTHOR]

Evidence for a vital role of soil mineral matrix interactions in lipid preservation is steadily increasing. However, it remains unclear whether solvent-extractable (‘free’) or hydrolyzable (‘bound’) lipids, including molecular proxies, e.g., for cutin and suberin, are similarly affected by different stabilization mechanisms in soil (i.e., aggregation or organo-mineral association). To provide insights into the effect of these stabilization mechanisms on lipid composition and preservation, we investigated free and bound lipids in particulate and mineral soil fractions, deriving from sand- and silt-/clay-sized aggregates from a forest subsoil. While free lipids accumulated in sand-sized aggregates, the more complex bound lipids accumulated in silt- and clay-sized aggregates, particularly in the respective mineral fractions < 6.3 µm (fine silt and clay). The presence of both, cutin and suberin markers indicated input of leaf- and root-derived organic matter to the subsoil. Yet, our cutin marker (9,10,ω-trihydroxyoctadecanoic acid) was not extracted from the mineral aggregate compartments < 6.3 µm, perhaps due to its chemical structure (i.e., cross-linking via several hydroxy groups, and thus higher ‘stability’, in macromolecular structures). Combined, these results suggest that the chemical composition of lipids (and likely also that of other soil organic matter compounds) governs interaction with their environment, such as accumulation in aggregates or association with mineral soil compartments, and thus indirectly influences their persistence in soil. [ABSTRACT FROM AUTHOR]

Water is the most important prerequisite for life and plays a major role during uptake and transport of nutrients. Roots are the plant organs that take up the major part of water, from the surrounding soil. Water uptake is related to the root system architecture, root growth, age and species dependent complex developmental changes in the anatomical structures. The latter is mainly attributed to the deposition of suberized barriers in certain layers of cell walls, such as endo- and exodermis. With respect to water permeability, changes in the suberization of roots are most relevant. Water transport or hydraulic conductivity of roots (Lp r ) can be described by the composite transport model and is known to be very variable between plant species and growth conditions and root developmental states. In this review, we summarize how anatomical structures and apoplastic barriers of roots can diversely affect water transport, comparing the model plant Arabidopsis with crop plants, such as barley and rice. Results comparing the suberin amounts and water transport properties indicate that the common assumption that suberin amount negatively correlates with water and solute transport through roots may not always be true. The composition, microstructure and localization of suberin may also have a great impact on the formation of efficient barriers to water and solutes. [ABSTRACT FROM AUTHOR]

Hydrogenolysis of cork has been examined using a range of precious metal catalysts studying the effect of the support, added base and solvent used. The addition of a catalyst and a base resulted in a bio-oil increase of 9.3–158% compared to when no catalyst was used along with an increase in the lipid yield of 113–258%. The change in the solvent to 2-methyl tetrahydrofuran from the original dioxane solvent system allowed for a change to a “greener” solvent as well as an increased bio-oil yield from 11.5 wt% to 42.6 wt%, in the absence of a base. [ABSTRACT FROM AUTHOR]

This study aimed to demonstrate that single-frequency (1 kHz) measurement of impedance phase angle ( Φ ) in root–soil systems is suitable for monitoring plant responses to environmental stresses. Potted wheat, soybean and maize plants were exposed to cadmium contamination, alkaline stress, drought or weed competition. Φ was detected at regular intervals between a ground and a plant electrode during plant development, at the end of which root and shoot biomass were measured. Each type of stress significantly reduced both Φ and the root and shoot dry mass, to an extent proportional to the stress level. The decrease in Φ was attributed to various physicochemical changes in root cell membranes, the accelerated maturation of the exo- and endodermis and altered root morphology. These stress responses modified the dielectric properties of the root tissues, influencing the apoplast and symplast pathways of the electrical current inside the roots. The stress-induced increase in the amount of electrically insulating lignin and suberin in root tissues was considered to be an influential factor in decreasing Φ . These results show that in pot experiments the measurement of the impedance phase angle in intact root systems is a potentially useful in situ method for detecting plant responses to stresses affecting roots. [ABSTRACT FROM AUTHOR]

Plant roots contribute substantially to the formation of stable soil organic matter (SOM), and there is evidence that species differ in their contribution to SOM stabilization. However, it remains unclear what specific root traits contribute to the three SOM stabilization mechanisms: recalcitrance against decomposition, occlusion in soil aggregates and interaction with soil minerals and metals. This is likely because research is highly fragmented and hampered by disciplinary barriers. By reviewing both plant functional ecology and soil science literature, we identified 18 different traits: architectural, morphological, physiological, symbiotic and chemical root characteristics, influencing the three SOM stabilization mechanisms. We found that traits increasing root recalcitrance promote short term stabilization by slowing decomposition, but that traits reducing recalcitrance contribute to long term stabilization by reaction of microbial products with mineral surfaces. Root length density, mycorrhizal association and rhizodeposition contribute to microaggregation. These and other traits, such as hemicellulose, soluble compounds, and high root branching index, favor macroaggregation. For stabilization by minerals and metals, those root traits promoting higher microbial activity: root nitrogen, hemicellulose and soluble compound concentrations are fundamental, while polyphenols, and litter Al and Mn also contribute to complexification and stabilization. Root depth distribution is the most important trait to control root C storage and stabilization in the subsoil; once roots have reached deeper soil layers, other traits, such as rhizodeposition and root chemistry, influence interaction with minerals and metals. Both mycorrhizal presence and root suberin promote SOC stabilization by means of all three mechanisms, indicating that these are important targets for continued work. Surprisingly, morphological traits commonly measured, namely specific root length and root diameter, poorly relate to stabilization mechanisms. Alternative traits such as chemical composition of the different root orders, root apex characteristics, quantity and quality of rhizodeposits as well as mycorrhizal fungal traits, should be further investigated. For future research, this review highlights the need to evaluate root decomposition and root-C stabilization concomitantly over the long-term, considering simultaneously root litter quality, estimated by root traits, the microbial products and properties of the soil matrix. The information accrued in this review can be used to evaluate the potential of plant species and cultivars to promote SOM stabilization, based on their root traits. [ABSTRACT FROM AUTHOR]

Abstract: Acyl‐lipids such as intracellular phospholipids, galactolipids, sphingolipids, and surface lipids play a crucial role in plant cells by serving as major components of cellular membranes, seed storage oils, and extracellular lipids such as cutin and suberin. Plant lipids are also widely used to make food, renewable biomaterials, and fuels. As such, enormous efforts have been made to uncover the specific roles of different genes and enzymes involved in lipid biosynthetic pathways over the last few decades. sn‐Glycerol‐3‐phosphate acyltransferases (GPAT) are a group of important enzymes catalyzing the acylation of sn‐glycerol‐3‐phosphate at the sn‐1 or sn‐2 position to produce lysophosphatidic acids. This reaction constitutes the first step of storage‐lipid assembly and is also important in polar‐ and extracellular‐lipid biosynthesis. Ten GPAT have been identified in Arabidopsis, and many homologs have also been reported in other plant species. These enzymes differentially localize to plastids, mitochondria, and the endoplasmic reticulum, where they have different biological functions, resulting in distinct metabolic fate(s) for lysophosphatidic acid. Although studies in recent years have led to new discoveries about plant GPAT, many gaps still exist in our understanding of this group of enzymes. In this article, we highlight current biochemical and molecular knowledge regarding plant GPAT, and also discuss deficiencies in our understanding of their functions in the context of plant acyl‐lipid biosynthesis. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Rapid wound healing would be critical for successful long‐term storage of fruits and vegetables. However, there was no direct evidence for the requirement and efficiency of oxygen in the fruit wound‐healing process. This study was conducted to investigate the role of oxygen in wound‐induced suberization by analyzing melanin, suberin polyphenolics (SPPs) and related enzymes in half‐cut kiwifruits exposed to 100%, 50%, 21% and 0% oxygen. RESULTS: By 3 days after wounding, the wound surface of kiwifruit in high (50 and 100%) oxygen appeared as a continuous layer of melanin and SPPs underneath, which effectively prevent excessive water vapor loss from the fruit halves. In contrast, melanin and SPPs deposition in the wound surface in 0% oxygen was significantly reduced, with high water vapor loss. Rapid decrease of soluble phenolic acids (caffeic, p‐coumaric, ferulic acids) was coupled with the increase of bound ferulic acid (coniferyl diacetate) especially in high oxygen by 9 days after wounding. Meanwhile, high oxygen enhanced peroxidase, catalase, phenylalanine ammonia‐lyase, and polyphenol oxidase activities. CONCLUSION: Oxygen is required for wound‐induced melanin and SPPs formation, and high oxygen is effective in promoting wound suberization in postharvest kiwifruit. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The tree bark periderm confers the first line of protection against pathogen invasion and abiotic stresses. The phellogen (cork cambium) externally produces cork (phellem) cells that are dead at maturity; while metabolically active, these tissues synthesize cell walls, as well as cell wall modifications, namely suberin and waxes. Suberin is a heteropolymer with aliphatic and aromatic domains, composed of acylglycerols, cross-linked polyphenolics and solvent-extractable waxes. Although suberin is essentially ubiquitous in vascular plants, the biochemical functions of many enzymes and the genetic regulation of its synthesis are poorly understood. We have studied suberin and wax composition in four developmental stages of hybrid poplar (Populus tremula x Populus alba) stem periderm. The amounts of extracellular ester-linked acyl lipids per unit area increased with tissue age, a trend not observed with waxes. We used RNA-Seq deep-sequencing technology to investigate the cork transcriptome at two developmental stages. The transcript analysis yielded 455 candidates for the biosynthesis and regulation of poplar suberin, including genes with proven functions in suberin metabolism, genes highlighted as candidates in other plant species and novel candidates. Among these, a gene encoding a putative lipase/acyltransferase of the GDSL-motif family emerged as a suberin polyester synthase candidate, and specific isoforms of peroxidase and laccase genes were preferentially expressed in cork, suggesting that their corresponding proteins may be involved in cross-linking aromatics to form lignin-like polyphenolics. Many transcriptional regulators with possible roles in meristem identity, cork differentiation and acyl-lipid metabolism were also identified. Our work provides the first large-scale transcriptomic dataset on the suberin-synthesizing tissue of poplar bark, contributing to our understanding of tree bark development at the molecular level. Based on these data, we have proposed a number of hypotheses that can be used in future research leading to novel biological insights into suberin biosynthesis and its physiological function [ABSTRACT FROM AUTHOR]

Summary: Wound‐induced suberin deposition involves the temporal and spatial coordination of phenolic and fatty acid metabolism. Phenolic metabolism leads to both soluble metabolites that accumulate as defense compounds as well as hydroxycinnamoyl derivatives that form the basis of the poly(phenolic) domain found in suberized tissue. Fatty acid metabolism involves the biosynthesis of very‐long‐chain fatty acids, 1‐alkanols, ω‐hydroxy fatty acids and α,ω‐dioic acids that form a poly(aliphatic) domain, commonly referred to as suberin. Using the abscisic acid (ABA) biosynthesis inhibitor fluridone (FD), we reduced wound‐induced de novo biosynthesis of ABA in potato tubers, and measured the impact on the expression of genes involved in phenolic metabolism (StPAL1, StC4H, StCCR, StTHT), aliphatic metabolism (StCYP86A33, StCYP86B12, StFAR3, StKCS6), metabolism linking phenolics and aliphatics (StFHT) or acyl chains and glycerol (StGPAT5, StGPAT6), and in the delivery of aliphatic monomers to the site of suberization (StABCG1). In FD‐treated tissue, both aliphatic gene expression and accumulation of aliphatic suberin monomers were delayed. Exogenous ABA restored normal aliphatic suberin deposition in FD‐treated tissue, and enhanced aliphatic gene expression and poly(aliphatic) domain deposition when applied alone. By contrast, phenolic metabolism genes were not affected by FD treatment, while FD + ABA and ABA treatments slightly enhanced the accumulation of polar metabolites. These data support a role for ABA in the differential induction of phenolic and aliphatic metabolism during wound‐induced suberization in potato. [ABSTRACT FROM AUTHOR]

Many plant tissues fluoresce due to the natural fluorophores present in cell walls or within the cell protoplast or lumen. While lignin and chlorophyll are well-known fluorophores, other components are less well characterized. Confocal fluorescence microscopy of fresh or fixed vibratome-cut sections of radiata pine needles revealed the presence of suberin, lignin, ferulate, and flavonoids associated with cell walls as well as several different extractive components and chlorophyll within tissues. Comparison of needles in different physiological states demonstrated the loss of chlorophyll in both chlorotic and necrotic needles. Necrotic needles showed a dramatic change in the fluorescence of extractives within mesophyll cells from ultraviolet (UV) excited weak blue fluorescence to blue excited strong green fluorescence associated with tissue browning. Comparisons were made among fluorophores in terms of optimal excitation, relative brightness compared to lignin, and the effect of pH of mounting medium. Fluorophores in cell walls and extractives in lumens were associated with blue or green emission, compared to the red emission of chlorophyll. Autofluorescence is, therefore, a useful method for comparing the histology of healthy and diseased needles without the need for multiple staining techniques, potentially aiding visual screening of host resistance and disease progression in needle tissue. [ABSTRACT FROM AUTHOR]

Quick suberin-based healing after wounding played a protective role for plant to prevent further damage. In this study, the stimulative effect of exogenous abscisic acid (ABA) on wound suberization in postharvest kiwifruit was evaluated through suberin staining with toluidine blue O as well as the determination of suberin phenolics and aliphatics in wound tissue. Furthermore, to reveal the regulatory involvement of ABA in wound suberization, comparative quantitative proteomics and transcriptomics analyses based on iTRAQ and qRT-PCR technique were performed. In proteomics levels, a total of 95 protein species consistently showed differential abundance between ABA and control, including 29 down-regulated and 66 up-regulated protein species. The Kyoto Encyclopedia of Genes and Genomes (KEGG) with protein-protein interaction analyses revealed that ABA mainly affected the antioxidant system, phenylpropanoid metabolism and lipid metabolism associated with wound suberization. Based on the data of proteomics analysis, the differential expressions of genes encoding 11 selected protein species were confirmed by qRT-PCR analyses. GSH-Px, MDHAR, SOD, APX, POD, PAL, CCR, PPO, CYP86B1, DGGT and KCS11 were likely to be the key enzymes that involved the response of ABA to stimulate wound suberization by mediating the antioxidant system, phenylpropanoid metabolism and lipid metabolism. Biological significance Kiwifruit is susceptible to physical injury causing postharvest deterioration during harvest, transportation and storage. Therefore, quick healing is important for maintaining the postharvest quality of injured fruit. This work elucidated the potential role of ABA and the proteomic mechanism of its regulation in wound suberization of postharvest kiwifruit. [ABSTRACT FROM AUTHOR]

• The skin dynamics development of two pear cultivars and their mutants were analyzed. • The key genes and metabolites involved in russet skin formation were identified. • A set of TFs was predicted as putative regulators of russet skin formation. • We emphasis on exploring the underlying mechanisms of russet pear skin formation. Different periderm development makes the partial and full russet skin of pear fruit, which negatively influence pear fruit appearance quality. The switch gene for russet skin formation and the functional conservation of the homologs among different species showed to have multiple significance to clarify the transcriptional network underlying russet skin formation. In this study, two pear cultivars coupled with their mutants were used to explore the underlying molecular regulatory network of russet skin formation. RNA-sequencing and metabolomics were used to identify the key pathways and switch genes involved in russet skin formation, and identified genes involved in lignin biosynthesis, suberin biosynthesis, and suberin transporters. Additionally, a set of transcription factors was identified via coexpression network analysis and differential expression analysis, including PbMYB308, PbbHLH49, PbWRKY24 , and PbNAC40 , which had a high correlation with russet skin-related genes. These genes were predicted as putative regulators involved in russet pear skin formation. qRT–PCR was performed to validate the transcriptome data. Two varieties and their mutants were used for the first time to explore the switch genes and underlying mechanisms of russet formation. We concentrated on the russet skin development in pear fruit, with an emphasis on exploring the underlying regulatory mechanisms. [ABSTRACT FROM AUTHOR]

Russeting is characterized by a particular rough and brown phenotype, which is mainly due to the accumulation of suberin in the inner part of the epidermal cell walls. In our previous bulk transcriptomic analysis, comparing fully russeted, and waxy apple varieties, showed, in apple fruit skin, a massive decreased expression of cutin, wax and some pentacyclic triterpene biosynthesis genes in the russeted varieties, with an expected concomitant enhanced expression of the suberin biosynthetic genes. In the present work, we performed a deep investigation of the aliphatic composition of the cutin, suberin, waxes, and triterpenes in the waxy and russeted patches of the semi-russeted apple variety “Cox Orange Pippin.” A targeted gene expression profiling was performed to validate candidate genes which were identified in our previous work and might be involved in the respective metabolic pathways. Our results showed that a decrease of cuticular waxes, ursolic acid and oleanolic acid, accompanied by an accumulation of alkyl-hydroxycinamates and betulinic acid, occurs in the russeted patches. The suberin monomer composition is characterized by specific occurrence of 20, 22, and 24 carbon aliphatic chains, whereas cutin is mainly represented by common C16 and C18 aliphatic chains. This work depicts, for the first time in apple, the complex composition of suberin, cutin, waxes and triterpenes, and confirms the strong interplay between these epidermal polymers in apple fruit skin.

The analysis of the effects of cadmium (Cd) on plant cells is crucial to understand defense mechanisms and adaptation strategies of plants against Cd toxicity. In this study, we examined stress-related enzyme activities after one and seven days of Cd application and the ultrastructure of roots of Pisum sativum L. after seven days of Cd treatment (10, 50, 100, and 200 μM CdSO4). Our results showed that phenylalanine ammonia-lyase (PAL) activity and the amount of Cd accumulated in the roots were significantly positively correlated with the Cd concentration used in our experiment. However, Cd caused a decrease of all studied antioxidative enzyme activities (i.e., catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX)). The analysis of the ultrastructure (TEM) showed various responses to Cd, depending on Cd concentrations. In general, lower Cd concentrations (50 and 100 μM CdSO4) mostly resulted in increased amounts of oil bodies, plastolysomes and the accumulation of starch granules in plastids. Meanwhile, roots treated with a higher concentration of Cd (200 μM CdSO4) additionally triggered protective responses such as an increased deposition of suberin lamellae in the endodermal cell walls. This indicates that Cd induces a complex defense response in root tissues.