Cuticular Wax Research Articles

AtMYB41 acts as a dual-function transcription factor that regulates the formation of lipids in an organ- and development-dependent manner.

The plant cuticle controls non-stomatal water loss and can serve as a barrier against biotic agents, whereas the heteropolymer suberin and its associated waxes are deposited constitutively at specific cell wall locations. While several transcription factors controlling cuticle formation have been identified, those involved in the transcriptional regulation of suberin biosynthesis remain poorly characterized. The major goal of this study was to further analyse the function of the R2R3-Myeloblastosis (MYB) transcription factor AtMYB41 in formation of the cuticle, suberin, and suberin-associated waxes throughout plant development. For functional analysis, the organ-specific expression pattern of AtMYB41 was analysed and Atmyb41ge alleles were generated using the CRISPR/Cas9 system. These were investigated for root growth and water permeability upon stress. In addition, the fatty acid, wax, cutin, and suberin monomer composition of different organs was evaluated by gas chromatography. The characterization of Atmyb41ge mutants revealed that AtMYB41 negatively regulates the production of cuticular lipids and fatty acid biosynthesis in leaves and seeds, respectively. Remarkably, biochemical analyses indicate that AtMYB41 also positively regulates the formation of cuticular waxes in stems of Arabidopsis thaliana. Overall, these results suggest that the AtMYB41 acts as a negative regulator of cuticle and fatty acid biosynthesis in leaves and seeds, respectively, but also as a positive regulator of wax production in A. thaliana stems.

Evaluation of Blue Honeysuckle Berries (Lonicera caerulea L.) Dried at Different Temperatures: Basic Quality, Sensory Attributes, Bioactive Compounds, and In Vitro Antioxidant Activity.

This study aims to comprehensively investigate the effects of hot-air dehydration on the quality of blue honeysuckle berries (Lonicera caerulea L.). The results demonstrated that drying with hot air at 40-65 °C for 7-72 h resulted in blue honeysuckle berries with a moisture content of 0.21-1.10 g H2O/g dry weight. Generally, low to medium temperatures (40-55 °C) showed a better effect on the quality than high temperatures (60-65 °C). Specifically, drying at 40 °C exclusively resulted in better retention of cuticular wax, the best sensory appearance, and the highest total phenolic content. Drying at 45 °C and 50 °C resulted in the highest antioxidant capacity and the optimal sensory flavor. Drying at 55 °C led to the highest soluble solid/acid ratio, ascorbic acid concentration, total flavonoid, and total anthocyanin. The work introduces an innovative raw berry product and provides a comprehensive practical and theoretical framework for convective dehydration of blue honeysuckle berries.

Degradation mechanism of cuticular wax composition and surface properties of bamboo culm during storage

Cuticular wax on bamboo culm forms a kind of protective biointerface during growing and degrades after harvesting leading to the deterioration of surface quality and protection function during storage. The degradation mechanism of the cuticular wax and surface property of harvested bamboo culm during storage is still unclear. To understand it, the microstructure of cuticular wax on the harvested bamboo culm was characterized and composition content was analyzed by GC-MS as well as the contact angle and color of bamboo culm surface were tested after the bamboo culm was stored in four simulated seasons: spring, summer, autumn and winter. The results showed that the more wax deposited on bamboo culm surface during storage, and the thickness of cuticular wax increased. During storage, the content of alkanes, alcohols and total ketone in bamboo culm cuticular wax decreased as well as the contents of terpenoids and esters increased. This suggested that the degradation of cuticular wax on bamboo culm should be due to the hydrolysis of alkane into fatty acids and terpenoids.The surface contact angle of stored bamboo culm decreased and the color of bamboo culm changed. The contact angle of the stored bamboo culm surface reduced 12.24%, 25.53%, 9.76%, 1.85% compared with the fresh bamboo culm. The surface color of bamboo culm was related to the content of cuticular wax and weight loss of bamboo culm and was the joint function of weight loss and wax content change.

Soil pH is the Primary Factor Driving the Transformation of Plant Cuticular Wax in Saline Soils

Soil pH is the Primary Factor Driving the Transformation of Plant Cuticular Wax in Saline Soils

A long non-coding RNA functions as a competitive endogenous RNA to modulate TaNAC018 by acting as a decoy for tae-miR6206.

Increasing evidence indicates a strong correlation between the deposition of cuticular waxes and drought tolerance. However, the precise regulatory mechanism remains elusive. Here, we conducted a comprehensive transcriptome analysis of two wheat (Triticum aestivum) near-isogenic lines, the glaucous line G-JM38 rich in cuticular waxes and the non-glaucous line NG-JM31. We identified 85,143 protein-coding mRNAs, 4,485 lncRNAs, and 1,130 miRNAs. Using the lncRNA-miRNA-mRNA network and endogenous target mimic (eTM) prediction, we discovered that lncRNA35557 acted as an eTM for the miRNA tae-miR6206, effectively preventing tae-miR6206 from cleaving the NAC transcription factor gene TaNAC018. This lncRNA-miRNA interaction led to higher transcript abundance for TaNAC018 and enhanced drought-stress tolerance. Additionally, treatment with mannitol and abscisic acid (ABA) each influenced the levels of tae-miR6206, lncRNA35557, and TaNAC018 transcript. The ectopic expression of TaNAC018 in Arabidopsis also improved tolerance toward mannitol and ABA treatment, whereas knocking down TaNAC018 transcript levels via virus-induced gene silencing in wheat rendered seedlings more sensitive to mannitol stress. Our results indicate that lncRNA35557 functions as a competing endogenous RNA to modulate TaNAC018 expression by acting as a decoy target for tae-miR6206 in glaucous wheat, suggesting that non-coding RNA has important roles in the regulatory mechanisms responsible for wheat stress tolerance.

Cuticle properties, wax composition, and crystal morphology of Hami melon cultivars (Cucumis melo L.) with differential resistance to fruit softening

Cuticle wax chemicals are cultivar-dependent and contribute to storage quality. Few research reported on wax analysis between melting flesh-type (MF; ‘Jinhuami 25’) and nonmelting flesh-type (NMF; ‘Xizhoumi 17’ and ‘Chougua’) Hami melons. Chemicals and crystal structures of Hami melon cuticular wax, cell wall metabolism related to fruit melting, and fruit physiology were analyzed to observe wax functions. Results showed that Hami melon cuticle wax predominantly consists of esters, alkanes, alcohols, aldehydes, and terpenoids. MF-type has a lower alkane/terpenoid ratio, concomitant to its higher weight loss and cuticle permeability. Micromorphology of wax crystals appears as numerous platelets with irregular crystals, and the transformation of wax structure in NMF Hami melon is delayed. Waxy components affect cell wall metabolism and physiological quality, which results in the pulp texture difference between MF-type and NMF-type during storage. Results provide a reference for the regulation of wax synthesis in both types of melons.

1-MCP treatment improves the postharvest quality of Jinxiu yellow peach by regulating cuticular wax composition and gene expression during cold storage.

This study aimed to analyze the effect of 1-methylcyclopropene (1-MCP) treatment on the postharvest quality, epidermal wax morphology, composition, and gene expression of Jinxiu yellow peach during cold storage. The results showed that 1-MCP treatment could maintain the postharvest quality of peach fruit as compared to control (CK) during cold storage. The wax crystals of peach fruit were better retained by 1-MCP, and they still existed in 0.6 and 0.9 µL/L 1-MCP treated fruit at 36 days. The total wax content in all the fruit increased first and then decreased during cold storage. Meanwhile, n-alkanes and primary alcohols were the main wax components. Compared to CK, 1-MCP treatment could delay the reduction of wax content during cold storage. The correlation analysis indicated that the postharvest quality of yellow peach was mainly affected by the contents of fatty acids and triterpenoids in cuticular wax. The transcriptomics results revealed PpaCER1, PpaKCS, PpaKCR1, PpaCYP86B1, PpaFAR, PpaSS2, and PpaSQE1 played the important roles in the formation of peach fruit wax. 1-MCP treatment upregulated PpaCER1 (18785414, 18786441, and 18787644), PpaKCS (18774919, 18789438, and 18793503), PpaKCR1 (18790432), and PpaCYP86B1 (18789815) to deposit more n-alkanes and fatty acids during cold storage. This study could provide a new perspective for regulating the postharvest quality of yellow peach in view of the application of cuticular wax. PRACTICAL APPLICATION: 'Jinxiu' yellow peach fruit is favorable among consumers because of its high commercial value. However, it ripens and deteriorates rapidly during storage, leading to serious economic loss and consumer disappointment. The effect of 1-methylcyclopropene (1-MCP) treatment on the postharvest quality, epidermal wax morphology, composition, and genes regulation of 'Jinxiu' yellow peach during cold storage was assessed. Compared to control, 1-MCP treatment could retain the storage quality of yellow peach by affecting cuticular wax composition and gene expression. This study could provide new perspective for regulating the postharvest quality of yellow peach in view of the application of cuticular wax.

A reference-grade genome of the xerophyte Ammopiptanthus mongolicus sheds light on its evolution history in legumes and drought-tolerance mechanisms

Plants that grow in extreme environments represent unique sources of stress-resistance genes and mechanisms. Ammopiptanthus mongolicus (Leguminosae) is a xerophytic evergreen broadleaf shrub native to semi-arid and desert regions; however, its drought-tolerance mechanisms remain poorly understood. Here, we report the assembly of a reference-grade genome for A. mongolicus, describe its evolutionary history within the legume family, and examine its drought-tolerance mechanisms. The assembled genome is 843.07 Mb in length, with 98.7% of the sequences successfully anchored to the nine chromosomes of A. mongolicus. The genome is predicted to contain 47 611 protein-coding genes, and 70.71% of the genome is composed of repetitive sequences; these are dominated by transposable elements, particularly long-terminal-repeat retrotransposons. Evolutionary analyses revealed two whole-genome duplication (WGD) events at 130 and 58 million years ago (mya) that are shared by the genus Ammopiptanthus and other legumes, but no species-specific WGDs were found within this genus. Ancestral genome reconstruction revealed that the A. mongolicus genome has undergone fewer rearrangements than other genomes in the legume family, confirming its status as a “relict plant”. Transcriptomic analyses demonstrated that genes involved in cuticular wax biosynthesis and transport are highly expressed, both under normal conditions and in response to polyethylene glycol-induced dehydration. Significant induction of genes related to ethylene biosynthesis and signaling was also observed in leaves under dehydration stress, suggesting that enhanced ethylene response and formation of thick waxy cuticles are two major mechanisms of drought tolerance in A. mongolicus. Ectopic expression of AmERF2, an ethylene response factor unique to A. mongolicus, can markedly increase the drought tolerance of transgenic Arabidopsis thaliana plants, demonstrating the potential for application of A. mongolicus genes in crop improvement.

Dynamic relationships among pathways producing hydrocarbons and fatty acids of maize silk cuticular waxes.

The hydrophobic cuticle is the first line of defense between aerial portions of plants and the external environment. On maize (Zea mays L.) silks, the cuticular cutin matrix is infused with cuticular waxes, consisting of a homologous series of very long-chain fatty acids (VLCFAs), aldehydes, and hydrocarbons. Together with VLC fatty-acyl-CoAs (VLCFA-CoAs), these metabolites serve as precursors, intermediates and end-products of the cuticular wax biosynthetic pathway. To deconvolute the potentially confounding impacts of the change in silk microenvironment and silk development on this pathway, we profiled cuticular waxes on the silks of the inbreds B73 and Mo17, and their reciprocal hybrids. Multivariate interrogation of these metabolite abundance data demonstrates that VLCFA-CoAs and total free VLCFAs are positively correlated with the cuticular wax metabolome, and this metabolome is primarily affected by changes in the silk microenvironment and plant genotype. Moreover, the genotype effect on the pathway explains the increased accumulation of cuticular hydrocarbons with a concomitant reduction in cuticular VLCFA accumulation on B73 silks, suggesting that the conversion of VLCFA-CoAs to hydrocarbons is more effective in B73 than Mo17. Statistical modeling of the ratios between cuticular hydrocarbons and cuticular VLCFAs reveals a significant role of precursor chain length in determining this ratio. This study establishes the complexity of the product-precursor relationships within the silk cuticular wax-producing network by dissecting both the impact of genotype and the allocation of VLCFA-CoA precursors to different biological processes, and demonstrates that longer chain VLCFA-CoAs are preferentially utilized for hydrocarbon biosynthesis.

The Arabidopsis cytochrome P450 enzyme CYP96A4 is involved in the wound-induced biosynthesis of cuticular wax and cutin monomers.

The plant cuticle is composed of cuticular wax and cutin polymers and plays an essential role in plant tolerance to diverse abiotic and biotic stresses. Several stresses, including water deficit and salinity, regulate the synthesis of cuticular wax and cutin monomers. However, the effect of wounding on wax and cutin monomer production and the associated molecular mechanisms remain unclear. In this study, we determined that the accumulation of wax and cutin monomers in Arabidopsis leaves is positively regulated by wounding primarily through the jasmonic acid (JA) signaling pathway. Moreover, we observed that a wound- and JA-responsive gene (CYP96A4) encoding an ER-localized cytochrome P450 enzyme was highly expressed in leaves. Further analyses indicated that wound-induced wax and cutin monomer production was severely inhibited in the cyp96a4 mutant. Furthermore, CYP96A4 interacted with CER1 and CER3, the core enzymes in the alkane-forming pathway associated with wax biosynthesis, and modulated CER3 activity to influence aldehyde production in wax synthesis. In addition, transcripts of MYC2 and JAZ1, key genes in JA signaling pathway, were significantly reduced in cyp96a4 mutant. Collectively, these findings demonstrate that CYP96A4 functions as a cofactor of the alkane synthesis complex or participates in JA signaling pathway that contributes to cuticular wax biosynthesis and cutin monomer formation in response to wounding.

A chromosome level genome assembly of Pseudoroegneria Libanotica reveals a key Kcs gene involves in the cuticular wax elongation for drought resistance

BackgroundThe genus Pseudoroegneria (Nevski) Löve (Triticeae, Poaceae), whose genome symbol was designed as “St”, accounts for more than 60% of perennial Triticeae species. The diploid species Psudoroegneria libanotica (2n = 14) contains the most ancient St genome, exhibited strong drought resistance, and was morphologically covered by cuticular wax on the aerial part. Therefore, the St-genome sequencing data could provide fundamental information for studies of genome evolution and reveal its mechanisms of cuticular wax and drought resistance.ResultsIn this study, we reported the chromosome-level genome assembly for the St genome of Pse. libanotica, with a total size of 2.99 Gb. 46,369 protein-coding genes annotated and 71.62% was repeat sequences. Comparative analyses revealed that the genus Pseudoroegneria diverged during the middle and late Miocene. During this period, unique genes, gene family expansion, and contraction in Pse. libanotica were enriched in biotic and abiotic stresses, such as fatty acid biosynthesis which may greatly contribute to its drought adaption. Furthermore, we investigated genes associated with the cuticular wax formation and water deficit and found a new Kcs gene evm.TU.CTG175.54. It plays a critical role in the very long chain fatty acid (VLCFA) elongation from C18 to C26 in Pse. libanotica. The function needs more evidence to be verified.ConclusionsWe sequenced and assembled the St genome in Triticeae and discovered a new KCS gene that plays a role in wax extension to cope with drought. Our study lays a foundation for the genome diversification of Triticeae species and deciphers cuticular wax formation genes involved in drought resistance.

Effects of 1-methylcyclopropene on skin greasiness and quality of 'Yuluxiang’ pear during storage at 20°C

During storage at 20°C, specific pear cultivars may exhibit a greasy texture and decline in quality due to fruit senescence. Among these varieties, 'Yuluxiang’ is particularly susceptible to peel greasiness, resulting in significant economic losses. Therefore, there is an urgent need for a preservative that can effectively inhibit the development of greasiness. Previous studies have demonstrated the efficacy of 1-methylcyclopropene (1-MCP) in extending the storage period of fruits. We hypothesize that it may also influence the occurrence of postharvest peel greasiness in the 'Yuluxiang’ pears. In this study, we treated 'Yuluxiang’ pears with 1-MCP. We stored them at 20°C while analyzing the composition and morphology of the surface waxes, recording enzyme activities related to wax synthesis, and measuring indicators associated with fruit storage quality and physiological characteristics. The results demonstrate that prolonged storage at 20°C leads to a rapid increase in skin greasiness, consistent with the observed elevations in L*, greasiness score, and the content of total wax and greasy wax components. Moreover, there were indications that cuticular waxes underwent melting, resulting in the formation of an amorphous structure. In comparison to controls, the application of 1-MCP significantly inhibited increments in L* values as well as grease scores while also reducing accumulation rates for oily waxes throughout most stages over its shelf period, additionally delaying transitions from flaky-wax structures towards their amorphous counterparts. During the initial 7 d of storage, several enzymes involved in the biosynthesis and metabolism of greasy wax components, including lipoxygenase (LOX), phospholipase D (PLD), and β-ketoacyl-CoA synthase (KCS), exhibited an increase followed by a subsequent decline. The activity of LOX during early shelf life (0–7 d) and the KCS activity during middle to late shelf life (14–21 d) were significantly suppressed by 1-MCP. Additionally, 1-MCP effectively maintained firmness, total soluble solid (TSS) and titratable acid (TA) contents, peroxidase (POD), and phenylalanine ammonia-lyase (PAL) activities while inhibiting vitamin C degradation and weight loss. Furthermore, it restrained polyphenol oxidase (PPO) activity, ethylene production, and respiration rate increase. These findings demonstrate that 1-MCP not only delays the onset of peel greasiness but also preserves the overall storage quality of 'Yuluxiang’ pear at a temperature of 20°C. This study presents a novel approach for developing new preservatives to inhibit pear fruit peel greasiness and provides a theoretical foundation for further research on pear fruit preservation.

Chemical and Transcriptomic Analyses of Leaf Cuticular Wax Metabolism in Ammopiptanthus mongolicus under Osmotic Stress.

Plant cuticular wax forms a hydrophobic structure in the cuticle layer covering epidermis as the first barrier between plants and environments. Ammopiptanthus mongolicus, a leguminous desert shrub, exhibits high tolerances to multiple abiotic stress. The physiological, chemical, and transcriptomic analyses of epidermal permeability, cuticular wax metabolism and related gene expression profiles under osmotic stress in A. mongolicus leaves were performed. Physiological analyses revealed decreased leaf epidermal permeability under osmotic stress. Chemical analyses revealed saturated straight-chain alkanes as major components of leaf cuticular wax, and under osmotic stress, the contents of total wax and multiple alkane components significantly increased. Transcriptome analyses revealed the up-regulation of genes involved in biosynthesis of very-long-chain fatty acids and alkanes and wax transportation under osmotic stress. Weighted gene co-expression network analysis identified 17 modules and 6 hub genes related to wax accumulation, including 5 enzyme genes coding KCS, KCR, WAX2, FAR, and LACS, and an ABCG transporter gene. Our findings indicated that the leaf epidermal permeability of A. mongolicus decreased under osmotic stress to inhibit water loss via regulating the expression of wax-related enzyme and transporter genes, further promoting cuticular wax accumulation. This study provided new evidence for understanding the roles of cuticle lipids in abiotic stress tolerance of desert plants.

Transcription factors and plant hormones mediate wax metabolism in response to drought stress.

Plants have, throughout evolution, developed a hydrophobic cuticle to protect them from various stresses in the terrestrial environment. The cuticle layer is mainly composed of cutin and cuticular wax, a mixture of very-long-chain fatty acids and their derivatives. With the progress of transcriptome sequencing and other research methods, the key enzymes, transporters and regulatory factors in wax synthesis and metabolism have been gradually identified, especially the study on the regulation of wax metabolism by transcription factors and others in response to plant stress has become a hot topic. Drought is a major abiotic stress that limits plant growth and crop productivity. Plant epidermal wax prevents non-stomatal water loss and improves water use efficiency to adapt to arid environments. In this study, the ways of wax synthesis, transport, metabolism and regulation at different levels are reviewed. At the same time, the regulation of wax by different transcription factors and plant hormones in response to drought is elaborated, and key research questions and important directions for future solutions are proposed to enhance the potential application of epidermal wax in agriculture and the environment.

Identification and application of an exocarp-preferential promoter for genetic engineering of tomato fruit.

Tomato (Solanum lycopersicum) is a globally cultivated crop with great economic value. The exocarp determines the appearance of tomato fruit and protects it from various biotic and abiotic challenges at both pre-harvest and post-harvest stages. However, no tomato exocarp-specific promoter is currently available, which hinders exocarp-based genetic engineering. Here, we identified by RNA sequencing and reverse transcription-quantitative PCR analyses that the tomato gene SlPR10 (PATHOGENESIS RELATED 10) was abundantly and predominantly expressed in the exocarp. A fluorescent reporter expressed by a 2087-bp SlPR10 promoter (pSlPR10) was mainly detected in the exocarp of transgenic tomato plants of both Ailsa Craig and Micro-Tom cultivars. This promoter was further utilized for transgenic expression of SlANT1 and SlMYB31 in tomato, which are master regulators of anthocyanin and cuticular wax biosynthesis, respectively. pSlPR10-driven SlANT1 expression resulted in anthocyanin accumulation in the exocarp, conferring gray mold resistance and extended shelf life to the fruit, while SlMYB31 expression led to waxy thickening in the fruit skin, delaying water loss and also extending fruit shelf life. Intriguingly, pSlPR10 and two other weaker tomato exocarp-preferential promoters exhibited coincided expression specificities in the gynophore of transgenic Arabidopsis (Arabidopsis thaliana) plants, providing not only an inkling of evolutionary homology between tomato exocarp and Arabidopsis gynophore but also useful promoters for studying gynophore biology in Arabidopsis. Collectively, this work reports a desirable promoter enabling targeted gene expression in tomato exocarp and Arabidopsis gynophore and demonstrates its usefulness in genetic improvement of tomato fruit quality.

Genomic analysis reveals phylogeny of Zygophyllales and mechanism for water retention of a succulent xerophyte.

Revealing the genetic basis for stress-resistant traits in extremophile plants will yield important information for crop improvement. Zygophyllum xanthoxylum, an extant species of the ancient Mediterranean, is a succulent xerophyte that can maintain a favorable water status under desert habitats; however, the genetic basis of this adaptive trait is poorly understood. Furthermore, the phylogenetic position of Zygophyllales, to which Z. xanthoxylum belongs, remains controversial. In this study, we sequenced and assembled the chromosome-level genome of Z. xanthoxylum. Phylogenetic analysis showed that Zygophyllales and Myrtales form a separated taxon as a sister to the clade comprising fabids and malvids, clarifying the phylogenetic position of Zygophyllales at whole-genome scale. Analysis of genomic and transcriptomic data revealed multiple critical mechanisms underlying the efficient osmotic adjustment using Na+ and K+ as "cheap" osmolytes that Z. xanthoxylum has evolved through the expansion and synchronized expression of genes encoding key transporters/channels and their regulators involved in Na+/K+ uptake, transport, and compartmentation. It is worth noting that ZxCNGC1;1 (cyclic nucleotide-gated channels) and ZxCNGC1;2 constituted a previously undiscovered energy-saving pathway for Na+ uptake. Meanwhile, the core genes involved in biosynthesis of cuticular wax also featured an expansion and upregulated expression, contributing to the water retention capacity of Z. xanthoxylum under desert environments. Overall, these findings boost the understanding of evolutionary relationships of eudicots, illustrate the unique water retention mechanism in the succulent xerophyte that is distinct from glycophyte, and thus provide valuable genetic resources for the improvement of stress tolerance in crops and insights into the remediation of sodic lands.

Increased nutritional quality of rice grains and migration mechanisms of selenium by spraying a foliar selenium-rich nutrient solution

Foliar application of selenium (Se) is an effective method for biofortification in rice, to ensure that sufficient Se is supplied by the crop to maintain human health. In order to improve Se concentration in rice and meet the daily recommended intake for humans, a foliar Se fertilizer was applied in five regions of Liaoning and Jilin provinces, China, and its effects on rice quality, leaf morphology, and wax characteristics were assessed in field tests. The effects of alkyl polyglycosides (APG) in the Se fertilizer were evaluated, and epicuticular waxes were measured to analyze the effects of the fertilizer on plant water status. The Se fertilizer effectively enhanced organic Se levels in rice (p < 0.05), ranging from 599.8 to 2002.0 µg kg−1. An intake of 50 g d−1 of Se-enriched rice can meet nutritional requirements, with total Se intake ranging from 30.0 to 100.1 µg d−1. The Se fertilizer increased the protein content and decreased the proportion of chalky rice (p < 0.05). APG increased the wettability of Se fertilizer on the surface of leaves, so Se could be better absorbed into the leaves and accumulate in rice. The Se fertilizer increased the epicuticular wax so that moisture loss from leaves was reduced. Mean cuticular wax thicknesses were 2.36 and 2.25 µg cm2 in Daohuaxiang and Wuyou 4, respectively. These results suggest a link between the quality of rice and epicuticular wax thickness, and the foliar application of Se fertilizer shows promise for increasing Se content in rice grown in Se deficient soils.

Extraction and characterisation of cuticular waxes from Physalis peruviana calyx

SummaryWaxes play an important role in maintaining fruit quality and shelf‐life extension because they are naturally effective in blocking the migration of moisture. In this work, cuticular waxes from Physalis peruviana calyx (PPC) were extracted and characterised as potentially hydrophobic materials. Extraction was carried out using the Soxhlet technique with two non‐polar solvents, hexane and petroleum ether, and one polar solvent, ethanol. The extraction yield, lipid characterisation, and hydrophobic potential of cuticular waxes from PPC were analysed and compared using thin‐layer chromatography (TLC), attenuated total reflectance‐infrared spectroscopy (ATR‐IR), GC–MS chromatogram (FAMES), and wetting contact angle. Extraction using hexane was the most efficient method (yield of 9.61 ± 0.37%) for obtaining cuticular waxes with better hydrophobic properties, characterised by a contact angle of = 107.37 ± 1.0° and a hysteresis contact angle of 11° due mainly to the presence of functional groups desirable and characteristic of vegetable waxes. Greater texture homogeneity visualised using optical microscopy and the presence of capric acid (70.97%) as a major component of low‐molecular‐weight fatty acids were observed in this extract. Due to their biodegradable, potentially antifungal, and hydrophobic properties, cuticular waxes from PPC have the potential to replace synthetic waxes in industrial applications.

Differential changes in cuticular wax affect the susceptibility to fruit decay in pitaya after harvest: A cultivar comparative study

Pitaya (Hylocereus undatus) fruit is susceptible to pathogens that induce fruit decay after harvest. Cuticular waxes covering the outermost plant surfaces are the first site of plant-environment interactions; however, their changes in response to fruit decay are under-researched. Herein, the surface microstructures and chemical composition of wax on pitayas, as well as their changes in response to fruit decay, were comparatively studied. The varieties ‘Baishuijing’ (BSJ) and ‘Hongshuijing’ (HSJ) were examined after harvest. The fruit appearance, morphology, and wax composition differed between cultivars. The surface of both pitaya cultivars was smooth, although traces of granules and a thicker lipid layer were observed using histochemical staining in HSJ than in BSJ, as well as a higher cuticular wax content. Fruit decay rate increased rapidly in both cultivars under room storage conditions, and greater sensitivity to pathogens was found in BSJ than HSJ. As well as the occurrence of fruit decay, the total wax coverage, very-long-chain primary alcohols, aldehydes, fatty acids, and triterpenoids decreased in BSJ, while remaining relatively stable in HSJ. Correspondingly, the relative gene expression levels of HuKCS11 (−1, 2, and 3), HuKCS17, and HuKCS19 (for the elongation of very-long-chain fatty acids), HuCER1 (for aldehydes or n-alkanes), HuFAR (−1 and 2) (for primary alcohols), HuBAS1 (−1, 3, and 4) (for β-amyrin), and HuLUS1 (for lupeol) were considerably modified following fruit senescence during storage. The difference in surface topography and wax accumulation between cultivars might have affected pathogen susceptibility after harvest. These results may help when choosing varieties of pitaya based on surface characteristics and cuticular chemicals. They may also help to optimize strategies for postharvest preservation and storage.

The cuticular wax on sorghum straw influenced soil microbial diversity and straw degradation in soil

The cuticular waxes cover living plant surface but the ecological significance of cuticular wax in crop straw returning to soil remains uncertain. This study focused on sorghum straw to investigate the bioactivity of cuticular waxes in the soil system. The surface of sorghum leaf, sheath and stem organs was covered with epicuticular wax crystals, which present a dull and glaucous wax layer. The leaf surface with wax exhibited an average contact angle of 83°, while after the wax removal the contact angle decreased to 53° on average, showing hydrophobic surface on the sorghum leaf. In total, six wax classes were identified across all organs, including aldehydes, alkanes, fatty acids, primary alcohols, sterols, and minor triterpenoids. The total wax coverage on leaves was 1.5 μg·cm−2, which was significantly lower than that on sheaths (20.6 μg·cm−2) and stems (6.3 μg·cm−2). The wax addition increased the proportions of Actinobacteria and Firmicutes by 24.42 % and 78.02 %, whereas decreased Proteobacteria and Acidobacteria by 16.32 % and 23.16 % on day 14 under higher wax rate. The microbial communities inhabiting returned straw surfaces also differed significantly between wax-retrained and wax-removed straw, as well as among leaf, stem, and sheath components, and at various decomposition stages. Wax addition increased soil microbial biomass carbon and nitrogen by 56.76 % and 25.60 % at higher rate, and soil enzyme activities (i.e., soil urease, soil acid phosphatase activity, soil sucrase activity). Wax removal significantly increased the decomposition rate of dry matter by 24.28 % and crude fiber by 27.22 % on day 154. These findings demonstrate that plant cuticular waxes maintain their bioactivities after entering the soil, which broadens our knowledge of the roles of plant cuticular waxes in ecosystems. Therefore, selecting efficient wax-degrading microorganisms would accelerate the nutrient cycling of crops in soil system.