Apple fruit periderms (russeting) induced by wounding or by moisture have the same histologies, chemistries and gene expressions

Russeting is a cosmetic defect of some fruit skins. Russeting (botanically: induction of periderm formation) can result from various environmental factors including wounding and surface moisture. The objective was to compare periderms resulting from wounding with those from exposure to moisture in developing apple fruit. Wounding or moisture exposure both resulted in cuticular microcracking. Cross-sections revealed suberized hypodermal cell walls by 4 d, and the start of periderm formation by 8 d after wounding or moisture treatment. The expression of selected target genes was similar in wound and moisture induced periderms. Transcription factors involved in the regulation of suberin (MYB93) and lignin (MYB42) synthesis, genes involved in the synthesis (CYP86B1) and the transport (ABCG20) of suberin monomers and two uncharacterized transcription factors (NAC038 and NAC058) were all upregulated in induced periderm samples. Genes involved in cutin (GPAT6, SHN3) and wax synthesis (KCS10, WSD1, CER6) and transport of cutin monomers and wax components (ABCG11) were all downregulated. Levels of typical suberin monomers (ω-hydroxy-C20, -C22 and -C24 acids) and total suberin were high in the periderms, but low in the cuticle. Periderms were induced only when wounding occurred during early fruit development (32 and 66 days after full bloom (DAFB)) but not later (93 DAFB). Wound and moisture induced periderms are very similar morphologically, histologically, compositionally and molecularly

Russeting in apple is initiated after exposure to moisture ends: Molecular and biochemical evidence

Exposure of the fruit surface to moisture during early development is causal in russeting of apple (Malus × domestica Borkh.). Moisture exposure results in formation of microcracks and de-creased cuticle thickness. Periderm differentiation begins in the hypodermis, but only after discon-tinuation of moisture exposure. Expressions of selected genes involved in cutin, wax and suberin synthesis were quantified, as were the wax, cutin and suberin compositions. Experiments were con-ducted in two phases. In Phase I (31 days after full bloom) the fruit surface was exposed to moisture for 6 or 12 d. Phase II was after moisture exposure had been discontinued. Unexposed areas on the same fruit served as unexposed controls. During Phase I, cutin and wax synthesis genes were down-regulated only in the moisture-exposed patches. During Phase II, suberin synthesis genes were up-regulated only in the moisture-exposed patches. The expressions of cutin and wax genes in the moisture-exposed patches increased slightly during Phase II, but the levels of expression were much lower than in the control patches. Amounts and compositions of cutin, wax and suberin were con-sistent with the gene expressions. Thus, moisture-induced russet is a two-step process: moisture exposure reduces cutin and wax synthesis, moisture removal triggers suberin synthesis. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Comparing anatomy, chemical composition, and water permeability of suberized organs in five plant species: wax makes the difference

AbstractMain conclusion The efficiency of suberized plant/environment interfaces as transpiration barriers is not established by the suberin polymer but by the wax molecules sorbed to the suberin polymer.Abstract Suberized cell walls formed as barriers at the plant/soil or plant/atmosphere interface in various plant organs (soil-grown roots, aerial roots, tubers, and bark) were enzymatically isolated from five different plant species (Clivia miniata, Monstera deliciosa, Solanum tuberosum, Manihot esculenta, and Malus domestica). Anatomy, chemical composition and efficiency as transpiration barriers (water loss in m s −1 ) of the different suberized cell wall samples were quantified.Results clearly indicated that there was no correlation between barrier properties of the suberized interfaces and the number of suberized cell layers, the amount of soluble wax and the amounts of suberin. Suberized interfaces of C. miniata roots, M. esculenta roots, and M. domestica bark periderms formed poor or hardly any transpiration barrier. Permeances varyingbetween 1.1 and 5.1 × 10 −8 ms −1 were very close to the permeance of water (7.4 × 10 −8 ms −1 ) evaporating from a water/ atmosphere interface. Suberized interfaces of aerial roots of M. deliciosa and tubers of S. tuberosum formed reasonable transpiration barriers with permeances varying between 7.4 × 10 −10 and 4.2 × 10 −9 m s −1 , which were similar to the upperrange of permeances measured with isolated cuticles (about 10 −9 ms −1 ). Upon wax extraction, permeances of M. deliciosa and S. tuberosum increased nearly tenfold, which proves the importance of wax establishing a transpiration barrier. Finally,highly opposite results obtained with M. esculenta and S. tuberosum periderms are discussed in relation to their agronomicalimportance for postharvest losses and tuber storage.Keywords Bark · Diffusion barrier · Periderm · Suberization · Storage root · Transpiration · Tuber · Water loss · Wa

Interaction of surfactants with Prunus laurocerasus leaf surfaces: time-dependent recovery of wetting contact angles depends on physico-chemical properties of surfactants

Abstract Background Surfactants are added to spray solutions because they significantly improve foliar uptake of active ingredients (AIs) into the leaves. It was intended to investigate whether surfactant solutions forming a dried deposit on Prunus leaf surfaces after they were sprayed, lead to structural and functional changes of the cuticle/atmosphere interface. This could potentially result in irreversibly enhanced leaf surface wetting, which should be of major disadvantage. Enhanced wetting could promote leaching of ions and promote leaf surface colonization with microorganisms. Results Prunus laurocerasus leaf surfaces were sprayed with aqueous solutions of non-ionic alcohol ethoxylates, a cationic, an anionic and one large polar surfactant. Directly after spraying and drying of the different surfactant solutions, wetting contact angles of deionized water (without surfactant) were significantly lower (between 6 and 54°) compared to wetting contact angles on untreated leaves (77°). Leaf surface wettability with deionized water was more pronounced with non-ionic alcohol ethoxylates (wetting contact angles ranging between 6 and 22°) compared to the other 3 surfactants (wetting contact angles ranging between 42 and 54°). Wetting contact angles of deionized water on leaf surfaces treated with non-ionic alcohol ethoxylates continuously increased again over time resulting in final wetting contact angles not different from untreated leaf surfaces. The time-dependent recovery of wetting contact angles was dependent on the degree of ethoxylation of the non-ionic alcohol ethoxylates. The wetting contact angle recovery rate was lower the higher the degree of ethoxylation of the alcohol ethoxylates was. With the cationic, anionic and large polar surfactant a recovery of wetting contact angles was not observed. In addition, on fully dehydrated and dead leaves wetting contact angle recovery was not observed for any of the tested surfactants after spraying and drying. Analytical determinations of the amounts of alcohol ethoxylates on the leaf surfaces after spraying and drying showed that amounts of alcohol ethoxylates decreased over time on the surface (24–72 h). Conclusion Our results indicate that non-ionic alcohol ethoxylates diffused within hours from the leaf surface into the leaf over time and thus fully disappeared from the leaf surface. This was not the case with the cationic, anionic and the large polar surfactants remaining on the leaf surface. Graphical Abstrac

Surfactant-induced enhancement of droplet adhesion in superhydrophobic soybean (Glycine max L.) leaves

This study performed with soybean (Glycine max L.), one of the most important crops for human and animal nutrition, demonstrates that changes in the leaf surface structure can increase the adhesion of applied droplets, even on superhydrophobic leaves, to reduce undesirable soil contamination by roll-off of agrochemical formulations from the plant surfaces. The wettability and morphology of soybean (Glycine max L.) leaf surfaces before and after treatment with six different surfactants (Agnique® SBO10 and five variations of nonionic surfactants) have been investigated. The leaf surface structures show a hierarchical organization, built up by convex epidermal cells (microstructure) and superimposed epicuticular platelet-shaped wax crystals (micro- to nanostructure). Chemical analysis of the epicuticular wax showed that 1-triacontanol (C30H61OH) is the main wax component of the soybean leaf surfaces. A water contact angle (CA) of 162.4° (σ = 3.6°) and tilting angle (TA) of 20.9° (σ = 10.0°) were found. Adherence of pure water droplets on the superhydrophobic leaves is supported by the hydrophilic hairs on the leaves. Agnique® SBO10 and the nonionic surfactant XP ED 75 increased the droplet adhesion and caused an increase of the TA from 20.9° to 85° and 90°, respectively. Scanning electron microscopy showed that surfactants with a hydrophilic–lipophilic balance value below 10 caused a size reduction of the epicuticular wax structures and a change from Cassie–Baxter wetting to an intermediate wetting regime with an increase of droplet adhesion

Asymmetric water transport in dense leaf cuticles and cuticle-inspired compositionally graded membranes

Most of the aerial organs of vascular plants are covered by a protective layer known as the cuticle, the main purpose of which is to limit transpirational water loss. Cuticles consist of an amphiphilic polyester matrix, polar polysaccharides that extend from the underlying epidermal cell wall and become less prominent towards the exterior, and hydrophobic waxes that dominate the surface. Here we report that the polarity gradient caused by this architecture renders the transport of water through astomatous olive and ivy leaf cuticles directional and that the permeation is regulated by the hydration level of the cutin-rich outer cuticular layer. We further report artificial nanocomposite membranes that are inspired by the cuticles’ compositionally graded architecture and consist of hydrophilic cellulose nanocrystals and a hydrophobic polymer. The structure and composition of these cuticle-inspired membranes can easily be varied and this enables a systematic investigation of the water transport mechanism.Peer ReviewedPostprint (published version

Rational Design Yields Molecular Insights on Leaf-Binding of Anchor Peptides

In times of a constantly growing world population and increasing demand for food, sustainable agriculture is crucial. The rainfastness of plant protection agents is of pivotal importance to reduce the amount of applied nutrients, herbicides, and fungicides. As a result of protective agent wash-off, plant protection is lost, and soils and groundwater are severely polluted. To date, rainfastness of plant protection products has been achieved by adding polymeric adjuvants to the agrochemicals. However, polymeric adjuvants will be regarded as microplastics in the future, and environmentally friendly alternatives are needed. Anchor peptides (APs) are promising biobased and biodegradable adhesion promoters. Although the adhesion of anchor peptides to artificial surfaces, such as polymers, has already been investigated in theory and experimentally, exploiting the adhesion to biological surfaces remains challenging. The complex nature and composition of biological surfaces such as plant leaves and fruit surfaces complicate the generation of accurate models. Here, we present the first detailed three-layered atomistic model of the surface of apple leaves and use it to compute free energy profiles of the adhesion and desorption of APs to and from that surface. Our model is validated by a novel fluorescence-based microtiter plate (MTP) assay that mimics these complex processes and allows for quantifying them. For the AP Macaque Histatin, we demonstrate that aromatic and positively charged amino acids are essential for binding to the waxy apple leaf surface. The established protocols should generally be applicable for tailoring the binding properties of APs to biological interfaces

Non-Coding RNA Analyses of Seasonal Cambium Activity in Populus tomentosa

Non-coding RNA, known as long non-coding RNA (lncRNA), circular RNA (circRNA) and microRNA (miRNA), are taking part in the multiple developmental processes in plants. However, the roles of which played during the cambium activity periodicity of woody plants remain poorly understood. Here, lncRNA/circRNA-miRNA-mRNA regulatory networks of the cambium activity periodicity in Populus tomentosa was constructed, combined with morphologic observation and transcriptome profiling. Light microscopy and Periodic Acid Schiff (PAS) staining revealed that cell walls were much thicker and number of cell layers was increased during the active-dormant stage, accompanied by abundant change of polysaccharides. The novel lncRNAs and circRNAs were investigated, and we found that 2037 lncRNAs and 299 circRNAs were differentially expression during the vascular cambium period, respectively. Moreover, 1046 genes were identified as a target gene of 2037 novel lncRNAs, and 89 of which were the miRNA precursors or targets. By aligning miRNA precursors to the 7655 lncRNAs, 21 lncRNAs were identified as precursors tof 19 known miRNAs. Furthermore, the target mRNA of lncRNA/circRNA-miRNA network mainly participated in phytohormone, cell wall alteration and chlorophyll metabolism were analyzed by GO enrichment and KEGG pathway. Especially, circRNA33 and circRNA190 taking part in the phytohormone signal pathway were down-regulated during the active-dormant transition. Xyloglucan endotransglucosylase/hydrolase protein 24-like and UDP-glycosyltransferase 85A1 involved in the cell wall modification were the targets of lncRNA MSTRG.11198.1 and MSTRG.1050.1. Notably, circRNA103 and MSTRG.10851.1 regulate the cambium periodicity may interact with the miR482. These results give a new light into activity–dormancy regulation, associated with transcriptional dynamics and non-coding RNA networks of potential targets identification