Melatonin treatment delays the softening of blueberry fruit by modulating cuticular wax metabolism and reducing cell wall degradation.

The effects of postharvest melatonin (MT) treatment on cuticular wax and cell wall metabolism in blueberry fruit (Vaccinium spp.) were evaluated. The results revealed that MT treatment maintained the cuticular wax rod-like structure and delayed wax degradation. The gas chromatography-mass spectrometry analysis results revealed that MT application changed the cuticular wax composition in blueberries, and 25 metabolic components were screened. The metabolic regulation of wax quality in blueberry fruit may therefore be influenced by MT. Additionally, MT slowed down pectin and cellulose degradation by reducing the activities of cell wall degrading enzymes like pectin methyl esterase polygalacturonase, ß-galactosidase, and cellulose in the later stages of storage. It also downregulated the transcriptional expression of related genes like VcPE, VcPG, VcBG6, and VcGAL1. Thus, MT prevented softening and senescence by postponing the degradation of the cell wall in postharvest blueberry fruit.

Uptake, Translocation, and Terminal Residue of Chlorantraniliprole and Difenoconazole in Rice: Effect of the Mixed-Application with Adjuvant.

Plant oil adjuvants are widely used to improve the utilization rate of pesticides. In this study, the uptake, translocation, and terminal residue of chlorantraniliprole and difenoconazole spraying with plant oil adjuvant in rice (Oryza sativa L.) were evaluated. After being mixed with the tank-mixed plant oil adjuvant, the cuticular wax of rice leaf was destroyed, which decreased the hydrophobicity of the rice leaf and facilitated the wetting, spreading, and penetration of pesticides onto the rice leaf. Additionally, the adjuvant promoted the translocation of difenoconazole from leaves to stems, but had little effect on the translocation of difenoconazole from leaves to roots, while inhibiting chlorantraniliprole translocation. Although adjuvant increased the initial deposition of chlorantraniliprole and difenoconazole on rice, the terminal residue was not significantly affected. The findings can promote the safe use of chlorantraniliprole and difenoconazole in rice production, especially when used with plant oil adjuvants. In the future, studies on more rice cultivars will be necessary to determine the generality of the conclusions.

Leaf cuticular waxes of wild-type Welsh onion (Allium fistulosum L.) and a wax-deficient mutant: Compounds with terminal and mid-chain functionalities.

Plant cuticles cover aerial organs to limit non-stomatal water loss and protect against insects and pathogens. Cuticles contain complex mixtures of fatty acid-derived waxes, with various chain lengths and diverse functional groups. To further our understanding of the chemical diversity and biosynthesis of these compounds, this study investigated leaf cuticular waxes of Welsh onion (Allium fistulosum L.) wild type and a wax-deficient mutant. Leaf waxes were extracted with chloroform, separated using thin layer chromatography (TLC), and analyzed using gas chromatography-mass spectrometry (GC-MS). The extracts contained typical wax compound classes found in nearly all plant lineages but also two uncommon compound classes. Analyses of characteristic MS fragmentation patterns followed by comparisons with synthetic standards identified the latter as very-long-chain ketones and primary ketols. The ketols were minor compounds, with chain lengths ranging from C28 to C32 and carbonyls mainly on C-18 and C-20 in wild type wax, and a C28 chain with C-16 carbonyl in the mutant. The ketones made up 70% of total wax in the wild type, consisting mainly of C31 isomers with carbonyl group on C-14 or C-16. In contrast, the mutant wax comprised only 4% ketones, with chain lengths C27 and C29 and carbonyls predominantly on C-12 and C-14, respectively. A two-carbon homolog shift between wild type and mutant was also observed in the primary alcohols (a major wax compound class), whilst alkanes exhibited a four-carbon shift. Overall, the compositional data shed light on possible biosynthetic pathways to wax ketones that can be tested in future studies.

Dynamic change of tea (Camellia sinensis) leaf cuticular wax in white tea processing for contribution to tea flavor formation.

Despite some studies on tea leaf cuticular wax, their component changes during dehydration and withering treatments in tea processing and suspected relation with tea flavor quality formation remain unknown. Here, we showed that tea leaf cuticular wax changed drastically in tea leaf development, dehydration, or withering treatment during tea processing, which affected tea flavor formation. Caffeine was found as a major component of leaf cuticular wax. Caffeine and inositol contents in leaf cuticular wax increased during dehydration and withering treatments. Comparisons showed that tea varieties with higher leaf cuticular wax loading produced more aroma than these with lower cuticular wax loading, supporting a positive correlation between tea leaf cuticular wax loading and degradation with white tea aroma formation. Dehydration or withering treatment of tea leaves also increased caffeine and inositol levels in leaf cuticular wax and triggered cuticular wax degradation into various molecules, that could be related to tea flavor formation. Thus, tea leaf cuticular waxes not only protect tea plants but also contribute to tea flavor formation. The study provides new insight into the dynamic changes of tea leaf cuticular waxes for tea plant protection and tea flavor quality formation in tea processing.

Characterization of Cuticular Wax in Tea Plant and Its Modification in Response to Low Temperature.

Cuticular wax ubiquitously covers the outer layer of plants and protects them against various abiotic and biotic stresses. Nevertheless, the characteristics of cuticular wax and its role in cold resistance in tea plants remain unclear. In our study, cuticular wax from different tissues, cultivars, and leaves during different spatio-temporal growth stages were characterized and compared in tea plants. The composition, distribution pattern, and structural profile of cuticular wax showed considerable tissue specificity, particularly in petals and seeds. During the spatial development of tea leaves, total wax content increased from the first to fifth leaf in June, while a decreasing pattern was observed in September. Additionally, the total wax content and number of wax compounds were enhanced, and the wax composition significantly varied with leaf growth from June to September. Ten cultivars showed considerable differences in total wax content and composition, such as the predominance of saturated fatty acids and primary alcohols in SYH and HJY cultivars, respectively. Correlation analysis suggested that n-hexadecanoic acid is positively related to cold resistance in tea plants. Further transcriptome analysis from cold-sensitive AJBC, cold-tolerant CYQ, and EC 12 cultivars indicated that the inducible expression of wax-related genes was associated with the cold tolerance of different cultivars in response to cold stress. Our results revealed the characterization of cuticular wax in tea plants and provided new insights into its modification in cold tolerance.

Effects of salicylic acid treatment on fruit quality and wax composition of blueberry (Vaccinium virgatum Ait).

The cuticular wax layer in fruit is a hydrophobic barrier which protects fruit from biotic and abiotic stress. The cuticular wax also affect fruit quality. This paper investigated the effects of salicylic acid on fruit quality and the cuticular wax in blueberry fruit during storage at room temperature (25 °C). 'Powderblue' blueberries (Vaccinium virgatum Ait) were treated with 1.0 mmol L-1 salicylic acid. The composition of cuticular wax layer and structure of epicuticular wax layer were analyzed at 4 d intervals during storage. Salicylic acid could efficiently delay the reduction of total wax content and affected the proportions of its constituents, including triterpenoids, esters, sterols, fatty acids, alcohols and alkanes. Our results also showed that there was no significant difference on the structure of epicuticular wax in salicylic acid treated fruits compared with that of the control. Salicylic acid delayed deterioration of blueberry fruit and enhanced its resistance to disease during storage.

Analysis of composition, morphology, and biosynthesis of cuticular wax in wild type bilberry (Vaccinium myrtillus L.) and its glossy mutant.

In this study, cuticular wax load, its chemical composition, and biosynthesis, was studied during development of wild type (WT) bilberry fruit and its natural glossy type (GT) mutant. GT fruit cuticular wax load was comparable with WT fruits. In both, the proportion of triterpenoids decreased during fruit development concomitant with increasing proportions of total aliphatic compounds. In GT fruit, a higher proportion of triterpenoids in cuticular wax was accompanied by a lower proportion of fatty acids and ketones compared to WT fruit as well as lower density of crystalloid structures on berry surfaces. Our results suggest that the glossy phenotype could be caused by the absence of rod-like structures in GT fruit associated with reduction in proportions of ketones and fatty acids in the cuticular wax. Especially CER26-like, FAR2, CER3-like, LTP, MIXTA, and BAS genes showed fruit skin preferential expression patterns indicating their role in cuticular wax biosynthesis and secretion.

Comparative analysis of the chemical composition and water permeability of the cuticular wax barrier in Welsh onion (Allium fistulosum L.).

Cuticular wax is a hydrophobic barrier between the plant surface and the environment that effectively reduces the loss of water. The surface of Welsh onion leaves is covered with wax. To explain the relationship between wax composition and water loss, we conducted this experiment. The water permeability and wax composition of leaves were determined by chemical and GC-MS methods. We performed a comparative analysis of the differences between the two cultivars and analyzed the relationship between water permeability and waxy components. Overall, the permeability to water was higher in 'Zhangqiu' than in 'Tenko'. The wax amount of 'Tenko' was 1.28-fold higher than that of 'Zhangqiu' and was primarily explained by the much larger amounts of ketones and alcohols in the former. Among the waxy components, C29 ketones were most abundant. There were substantial discrepancies in wax composition, total wax content, and water permeability between the two cultivars. The main reason for the discrepancy in water permeability may be the significantly lower aliphatic fraction in 'Zhangqiu' than in 'Tenko'. This study makes a vital contribution to drought resistance research on allium plants.

Compositional and morphological analyses of wax in northern wild berry species.

Aerial surfaces of plants are covered by a waxy cuticle protecting plants from excessive water loss and UV light. In the present study, composition and morphology of cuticular waxes of northern wild berry species bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), bog bilberry (V. uliginosum L.) and crowberry (Empetrum nigrum L.) were investigated. Scanning electron microscopy (SEM) revealed differences in epicuticular wax morphology, and gas chromatography-mass spectrometry (GC-MS) analysis confirmed variation in chemical composition of cuticular waxes between the berry species. The dominant compounds in bilberry and lingonberry cuticular waxes were triterpenoids, while fatty acids and alkanes were the dominant ones in bog bilberry and crowberry, respectively. Wax extracted by supercritical fluid extraction (SFE) from industrial press cakes of bilberry and lingonberry contained linoleic acid and γ-linolenic acid as the dominant compounds. Furthermore, in vitro sun protection factor (SPF) of berry waxes depicted good UV-B absorbing capacities.

Functional Overlap of Long-Chain Acyl-CoA Synthetases in Arabidopsis.

Long-chain acyl-CoA synthetases (LACSs) play diverse and essential roles in lipid metabolism. The genomes of model eukaryotic organisms encode multiple LACS genes, and the substrate specificities of LACS homologs often overlap substantially. Homologous LACSs tend to differ in their expression patterns, localizations, and, by extension, the metabolic pathways to which they contribute. The Arabidopsis genome encodes a family of nine LACS genes, which have been characterized largely by reverse genetic analysis of mutant phenotypes. Because of redundancy, distinguishing the contributions of some Arabidopsis LACS genes has been challenging. Here, we have attempted to clarify the functions of LACSs that functionally overlap by synopsizing the results of previous work, isolating a suite of higher-order mutants that were previously lacking, and analyzing oil, wax, cutin, cuticle permeability, fertility and growth phenotypes. LACS1, LACS2, LACS4, LACS8 and LACS9 all affect cuticular lipid metabolism, but have different precise roles. Seed set, seed weight and storage oil amounts of higher-order lacs1, lacs2, lacs4, lacs8 and lacs9 mutants vary greatly, with these traits subject to different effects of fertility and oil synthesis defects. LACS4, LACS8 and LACS9 have partially redundant roles in development, as lacs4 lacs8 and lacs4 lacs9 double mutants are dwarf. lacs4 lacs8 lacs9 triple mutants were not recovered, and are assumed to be non-viable. Together, these results sketch a complex network of functions and functional interactions within the Arabidopsis LACS gene family.

Comparative Analyses of Cuticular Waxes on Various Organs of Potato (Solanum tuberosum L.).

Complex mixtures of cuticular waxes coat plant surfaces to seal them against environmental stresses, with compositions greatly varying between species and possibly organs. This paper reports comprehensive analyses of the waxes on both above- and below-ground organs of potato, where total wax coverages varied between petals (2.6 µg/cm2), leaves, stems, and tubers (1.8-1.9 µg/cm2), and rhizomes (1.1 µg/cm2). The wax mixtures on above-ground organs were dominated by alkanes, occurring in homologous series of isomeric C25-C35 n-alkanes, C25-C35 2-methylalkanes, and C26-C34 3-methylalkanes. In contrast, below-ground organs had waxes rich in monoacylglycerols (C22-C28 acyls) and C18-C30 alkyl ferulates, together with fatty acids (rhizomes) or primary alcohols (tubers). The organ-specific wax coverages, compound class distribution, and chain length profiles suggest highly regulated activities of wax biosynthesis enzymes, likely related to organ-specific ecophysiological functions.