Accumulation Of Suberin Research Articles

Sodium silicate accelerates suberin accumulation at wounds of potato tuber by inducing phenylpropanoid pathway and fatty acid metabolism during healing

Although soluble silicate was reported to accelerate wound healing in muskmelon fruit through encouraging the deposition of lignin or free fatty acids, whether sodium silicate affects the biosynthesis, cross-linking and transport of suberin monomers during potato wound healing remains unknown. In this study, sodium silicate upregulated the expression and activity of 4-coumarate: coenzyme A ligase (4CL), phenylalanine ammonia lyase (PAL), and promoted the synthesis of phenolic acids (caffeic acid, p-coumaric acid, cinnamic acid, sinapic acid, and ferulic acid) in tuber wounds. Meanwhile, sodium silicate upregulated the expression of glycerol-3-phosphate acyltransferase (StGPAT), fatty acyl reductase (StFAR), long-chain acyl-CoA synthetase (StLACS), β-ketoacyl-CoA synthase (StKCS), and cytochrome P450 (StCYP86A33), and thus increased the levels of α, ω-diacids, ω-hydroxy acids, and primary alcohols in wounds. Sodium silicate also induced the expression of ω-hydroxy acid/fatty alcohol hydroxycinnamoyl transferase (StFHT), ABC transporter (StABCG), and promoted the deposition of suberin in wound surface, hence reducing tuber disease index and weight loss during healing. Taken together, sodium silicate may accelerate suberin accumulation at potato tubers wound through inducing the phenylpropanoid pathway and fatty acid metabolism.

Polystyrene nanoplastics induce cell type-dependent secondary wall reinforcement in rice (Oryza sativa) roots and reduce root hydraulic conductivity

Nanoplastics (NPs) have been demonstrated the ability to penetrate plant roots and cause stress. However, the extent of NPs penetration into various root tissues and the corresponding plant defense mechanisms remain unclear. This study examined the penetration and accumulation patterns of polystyrene nanoplastics (PS-NPs) in different cell types within rice roots, and explored how the roots quickly modify their cell wall structure in response. The findings showed that fully developed sclerenchyma cells in rice roots effectively prevented the invasion of PS-NPs. Meanwhile, PS-NPs triggered the accumulation of lignin and suberin in specific cells such as the exodermis, sclerenchyma, and xylem vessels. PS-NPs at a concentration of 50 mg L−1 increased cell wall thickness by 18.6 %, 21.1 %, and 22.4 % in epidermis, exodermis, and sclerenchyma cells, respectively, and decreased root hydraulic conductivity by 14.8 %. qPCR analysis revealed that PS-NPs influenced the cell wall synthesis pathway, promoting the deposition of lignin and suberin monomers on the secondary wall through the up-regulation of genes such as OsLAC and OsABCG. These results demonstrate that PS-NPs can induce cell type-specific strengthening of secondary walls and barrier formation in rice roots, suggesting the potential role of plant secondary wall development in mitigating NPs contamination risks in crops.

MYB24, MYB144, and MYB168 positively regulate suberin biosynthesis at potato tuber wounds during healing.

The essence of wound healing is the accumulation of suberin at wounds, which is formed by suberin polyphenolic (SPP) and suberin polyaliphatic (SPA). The biosynthesis of SPP and SPA monomers is catalyzed by several enzyme classes related to phenylpropanoid metabolism and fatty acid metabolism, respectively. However, how suberin biosynthesis is regulated at the transcriptional level during potato (Solanum tuberosum) tuber wound healing remains largely unknown. Here, 6 target genes and 15 transcription factors related to suberin biosynthesis in tuber wound healing were identified by RNA-seq technology and qRT-PCR. Dual luciferase and yeast one-hybrid assays showed that StMYB168 activated the target genes StPAL, StOMT, and St4CL in phenylpropanoid metabolism. Meanwhile, StMYB24 and StMYB144 activated the target genes StLTP, StLACS, and StCYP in fatty acid metabolism, and StFHT involved in the assembly of SPP and SPA domains in both native and wound periderms. More importantly, virus-induced gene silencing in S. tuberosum and transient overexpression in Nicotiana benthamiana assays confirmed that StMYB168 regulates the biosynthesis of free phenolic acids, such as ferulic acid. Furthermore, StMYB24/144 regulated the accumulation of suberin monomers, such as ferulates, α, ω-diacids, and ω-hydroxy acids. In conclusion, StMYB24, StMYB144, and StMYB168 have an elaborate division of labor in regulating the synthesis of suberin during tuber wound healing.

Feruloyl Glyceride Mitigates Tomato Postharvest Rot by Inhibiting Penicillium expansum Spore Germination and Enhancing Suberin Accumulation.

Postharvest rot, caused by Penicillium expansum, in tomatoes poses significant economic and health risks. Traditional control methods, such as the use of fungicides, raise concerns about pathogen resistance, food safety, and environmental impact. In search of sustainable alternatives, plant secondary metabolites, particularly phenolic compounds and their derivatives, have emerged as promising natural antimicrobials. Among these, feruloyl glyceride (FG), a water-soluble derivative of ferulic acid, stands out due to its antioxidant properties, antibacterial properties, and improved solubility. In this study, we provide evidence demonstrating FG is capable of inhibiting the spore germination of P. expansum and effectively reducing the incidence rate of Penicillium rot of tomatoes, without compromising quality. Electron microscopy observations combined with metabolite and transcriptomic analyses revealed that FG treatments resulted in enhanced suberin accumulation through promoting the expression of suberin synthesis related genes and, consequently, inhibited the growth and expansion of P. expansum on the fruits. This work sheds light on the mechanisms underlying FG's inhibitory effects, allowing its potential application as a natural and safe alternative to replace chemical fungicides for postharvest preservation.

Comprehensive analysis of KCS gene family in pear reveals the involvement of PbrKCSs in cuticular wax and suberin synthesis and pear fruit skin formation.

Cuticular wax, cutin and suberin polyesters covering the surface of some fleshy fruit are tightly associated with skin color and appearance.β-Ketoacyl-CoA synthase (KCS) is a rate-limiting enzyme participating in the synthesis of very-long-chain fatty acids (VLCFAs), the essential precursors of cuticular waxes and aliphatic monomers of suberin. However, information on the KCS gene family in pear genome and the specific members involved in pear fruit skin formation remain unclear. In the present study, we performed an investigation of the composition and amount of cuticular waxes, cutin and aliphatic suberin in skins of four sand pear varieties with distinct colors (russet, semi-russet, and green) and demonstrated that the metabolic shifts of cuticular waxes and suberin leading to the significant differences of sand pear skin color. A genome-wide identification of KCS genes from the pear genome was conducted and 35 KCS coding genes were characterized and analyzed. Expression profile analysis revealed that the KCS genes had diverse expression patterns among different pear skins and the transcript abundance of PbrKCS15, PbrKCS19, PbrKCS24, and PbrKCS28 were consistent with the accumulation of cuticular waxes and suberin in fruit skin respectively. Subcellular localization analysis demonstrated that PbrKCS15, PbrKCS19, PbrKCS24 and PbrKCS28 located on the endoplasmic reticulum (ER). Further, transient over-expression of PbrKCS15, PbrKCS19, and PbrKCS24 in pear fruit skins significantly increased cuticular wax accumulation, whereas PbrKCS28 notably induced suberin deposition. In conclusion, pear fruit skin color and appearance are controlled in a coordinated way by the deposition of the cuticular waxes and suberin. PbrKCS15, PbrKCS19, and PbrKCS24 are involved in cuticular wax biosynthesis, and PbrKCS28 is involved in suberin biosynthesis, which play essential roles in pear fruit skin formation. Moreover, this work provides a foundation for further understanding the functions of KCS genes in pear.

ФОРМИРОВАНИЕ ПОЯСКОВ КАСПАРИ В КОРНЯХ ПОЧТИ ИЗОГЕННЫХ ЛИНИЙ ЯЧМЕНЯ, ОТЛИЧАЮЩИХСЯ НАЛИЧИЕМ МЕЛАНИНОВОЙ ОКРАСКИ КОЛОСА

The influence of the BLP locus genes, which control the formation of black coloration of the spike glumes and grain pericarp on the formation of Casparian bands in Hordeum vulgare L. plants, was studied. The experiment was carried out with plants of the Bowman variety and three almost isogenic lines obtained on its basis: the BLP line, carrying one recombinant section from the donor of the trait of black coloration of the ear; a line with a dark gray mBLP grain and a line with a light gray gBLP grain, carrying recombinant regions in chromosomes 1H, 2H, 3H. Lignin and suberin deposition were assessed on transverse sections of root tissue. Lignin and suberin on histological sections were stained with an aqueous solution of berberine hemisulfate. On the 7th day after the start of germination, on sections made in the basal part of the root, luminescence with berberine revealed no differences between plants of different genotypes in the level of accumulation of lignin and suberin. On the 10th day, on sections of the basal part of the roots of the gBLP line, staining of the radial walls of the endoderm is noticeable, which indicates the deposition of lignin in the endoderm area, characteristic of the formation of Casparian bands, as well as in the area of metaxylem vessels. Thus, it was revealed that the gBLP genotype is characterized by accelerated formation of apoplastic barriers. The Bowman and gBLP genotypes we selected, which contrast in the rate of formation of Casparian bands, are a convenient object for further identifying the relationship between the rate of formation of Casparian bands and salt tolerance of plants.

Characterization of MdMYB68, a suberin master regulator in russeted apples.

Apple russeting is mainly due to the accumulation of suberin in the cell wall in response to defects and damages in the cuticle layer. Over the last decades, massive efforts have been done to better understand the complex interplay between pathways involved in the suberization process in model plants. However, the regulation mechanisms which orchestrate this complex process are still under investigation. Our previous studies highlighted a number of transcription factor candidates from the Myeloblastosis (MYB) transcription factor family which might regulate suberization in russeted or suberized apple fruit skin. Among these, we identified MdMYB68, which was co-expressed with number of well-known key suberin biosynthesis genes. To validate the MdMYB68 function, we conducted an heterologous transient expression in Nicotiana benthamiana combined with whole gene expression profiling analysis (RNA-Seq), quantification of lipids and cell wall monosaccharides, and microscopy. MdMYB68 overexpression is able to trigger the expression of the whole suberin biosynthesis pathway. The lipid content analysis confirmed that MdMYB68 regulates the deposition of suberin in cell walls. Furthermore, we also investigated the alteration of the non-lipid cell wall components and showed that MdMYB68 triggers a massive modification of hemicelluloses and pectins. These results were finally supported by the microscopy. Once again, we demonstrated that the heterologous transient expression in N. benthamiana coupled with RNA-seq is a powerful and efficient tool to investigate the function of suberin related transcription factors. Here, we suggest MdMYB68 as a new regulator of the aliphatic and aromatic suberin deposition in apple fruit, and further describe, for the first time, rearrangements occurring in the carbohydrate cell wall matrix, preparing this suberin deposition.

Disruption of the ABA1 encoding zeaxanthin epoxidase caused defective suberin layers in Arabidopsis seed coats.

Suberin, a complex polyester deposited in the seed coat outer integument, acts as a hydrophobic barrier to control the movement of water, ions, and gas. However, relatively little is known about the signal transduction involved in suberin layer formation during seed coat development. In this study, the effect of the plant hormone abscisic acid (ABA) on suberin layer formation in seed coats was investigated by characterizing mutations in Arabidopsis related to ABA biosynthesis and signaling. Seed coat permeability to tetrazolium salt was noticeably elevated in aba1-1 and abi1-1 mutants, but not significantly altered in snrk2.2/3/6, abi3-8, abi5-7, and pyr1pyl1pyl2pyl4 quadruple mutants compared with that in the wild-type (WT). ABA1 encodes a zeaxanthin epoxidase that functions in the first step of ABA biosynthesis. aba1-1 and aba1-8 mutant seed coats showed reduced autofluorescence under UV light and increased tetrazolium salt permeability relative to WT levels. ABA1 disruption resulted in decreased total seed coat polyester levels by approximately 3%, with a remarkable reduction in levels of C24:0 ω-hydroxy fatty acids and C24:0 dicarboxylic acids, which are the most abundant aliphatic compounds in seed coat suberin. Consistent with suberin polyester chemical analysis, RT-qPCR analysis showed a significant reduction in transcript levels of KCS17, FAR1, FAR4, FAR5, CYP86A1, CYP86B1, ASFT, GPAT5, LTPG1, LTPG15, ABCG2, ABCG6, ABCG20, ABCG23, MYB9, and MYB107, which are involved in suberin accumulation and regulation in developing aba1-1 and aba1-8 siliques, as compared with WT levels. Together, seed coat suberization is mediated by ABA and partially processed through canonical ABA signaling.

Cotton green fiber promotes suberin synthesis interfering cellulose deposition in the secondary cell wall

Naturally green cotton (NGC) represents one of two commercialized naturally colored cottons, but its application is limited in the textile industry for inferior productivity and fiber quality of NGC cultivars. NGC fiber deposits substantial suberin at maturation, possibly related to fiber green coloration. The effects of suberin deposition on fiber development and fiber yield and quality are still to be elucidated. In the present study, the green fiber gene (Lg) in upland cotton (Gossypium hirsutum L.) was cloned using map-based method. It was found that Lg encoded an R2R3-MYB transcription factor, promoting suberin synthesis and deposition in cotton fiber via regulating multiple suberin structural genes. Suberin accumulated in green fibers continuously from the beginning of the secondary cell wall synthesis, along with significantly inhibited cellulose deposition, leading to dramatically decreased fiber strength and lint percentage. Our data demonstrated that suberin accumulation significantly interfered with cellulose deposition in fiber secondary cell wall, which conferred low yield and inferior fiber quality to green-fiber cottons.

Understanding the changes of phenylpropanoid metabolism and lignin accumulation in wounded cassava root during postharvest storage

The postharvest deterioration of cassava (Manihot esculenta Crantz) root which was caused by the wounds has severely hampered the development of the cassava industry. In this study, the deterioration rate and weight loss, the transcription and enzyme activity of key genes in the phenylpropane metabolism, and the accumulation of lignin and suberin were examined during wound healing of cassava root. The results showed that the deterioration rate and weight loss of cassava-resistant variety SC9 were 4.1 and 1.8 times lower than those of the susceptible SC6 on the seventh day of storage. The activities of phenylalanine ammonia-lyase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD) of SC9 were significantly higher on the seventh day than at 0 h. By contrast with SC6, SC9 deposited a large amount of lignin and suberin in the wound site. The structural characteristics of wound healing tissues were analyzed by microscopic observation, revealing that the healing reaction of cassava roots prevented the penetration of toluidine blue and pathogen infection. The expression changes of genes related to the phenylpropanoid metabolism pathway and the accumulation of lignin during wound self-healing provide new ideas for solving postharvest deterioration of cassava roots.

Knockout of MITOGEN-ACTIVATED PROTEIN KINASE 3 causes barley root resistance against Fusarium graminearum.

The roles of mitogen-activated protein kinases (MAPKs) in plant-fungal pathogenic interactions are poorly understood in crops. Here, microscopic, phenotypic, proteomic, and biochemical analyses revealed that roots of independent transcription activator-like effector nuclease (TALEN)-based knockout lines of barley (Hordeum vulgare L.) MAPK 3 (HvMPK3 KO) were resistant against Fusarium graminearum infection. When co-cultured with roots of the HvMPK3 KO lines, F. graminearum hyphae were excluded to the extracellular space, the growth pattern of extracellular hyphae was considerably deregulated, mycelia development was less efficient, and number of appressoria-like structures and their penetration potential were substantially reduced. Intracellular penetration of hyphae was preceded by the massive production of reactive oxygen species (ROS) in attacked cells of the wild-type (WT), but ROS production was mitigated in the HvMPK3 KO lines. Suppression of ROS production in these lines coincided with elevated abundance of catalase (CAT) and ascorbate peroxidase (APX). Moreover, differential proteomic analysis revealed downregulation of several defense-related proteins in WT, and the upregulation of pathogenesis-related protein 1 (PR-1) and cysteine proteases in HvMPK3 KO lines. Proteins involved in suberin formation, such as peroxidases, lipid transfer proteins (LTPs), and the GDSL esterase/lipase (containing "GDSL" aminosequence motif) were differentially regulated in HvMPK3 KO lines after F. graminearum inoculation. Consistent with proteomic analysis, microscopic observations showed enhanced suberin accumulation in roots of HvMPK3 KO lines, most likely contributing to the arrested infection by F. graminearum. These results suggest that TALEN-based knockout of HvMPK3 leads to barley root resistance against Fusarium root rot.

MYB1R1 and MYC2 Regulate ω-3 Fatty Acid Desaturase Involved in ABA-Mediated Suberization in the Russet Skin of a Mutant of 'Dangshansuli' (Pyrus bretschneideri Rehd.).

Russeting, a disorder of pear fruit skin, is mainly caused by suberin accumulation on the inner part of the outer epidermal cell layers. ABA was identified as a crucial phytohormone in suberification. Here, we demonstrated that the ABA content in russet pear skin was higher than in green skin. Then, ABA was applied to explore the changes in phenotype and suberin composition coupled with RNA-Seq and metabolomics to investigate the probably regulatory pathway of ABA-mediated suberification. The results showed that ABA treatment increased the expression of ω-3 fatty acid desaturase (FAD) and the content of α-linolenic acid. We identified 17 PbFADs in white pear, and the expression of PbFAD3a was induced by ABA. In addition, the role of PbFAD3a in promoting suberification has been demonstrated by overexpression in Arabidopsis and VIGS assays in the fruitlets. GUS staining indicated that the promoter of PbFAD3a was activated by ABA. Furthermore, MYC2 and MYB1R1 have been shown to bind to the PbFAD3a promoter directly and this was induced by ABA via yeast one-hybrid (Y1H) screening and qRT–PCR. In summary, our study found that ABA induces the expression of MYC2 and MYB1R1 and activates the PbFAD3a promoter, contributing to the formation of russet pear skin. Functional identification of key transcription factors will be the goal of future research. These findings reveal the molecular mechanism of ABA-mediated suberization in the russet skin and provide a good foundation for future studies on the formation of russet skin.

Genome-wide identification and co-expression analysis of GDSL genes related to suberin formation during fruit russeting in pear

Glycine-aspartic acid‑serine-leucine (GDSL) type lipases/esterases genes play critical roles in plant development and are related to the responses to abiotic and biotic stress. However, little is known about the GDSL family in pear (Pyrus spp.). Studies have shown GDSL-domain proteins play key roles in suberin deposition. Suberin deposition in the fruit epidermis, also called russeting, is an important defect that negatively affects consumer's appeal in some fruit species, such as pear, apple and grapevine. Fruit russeting is mainly associated with cuticle microcracking and suberin accumulation in the inner part of the epidermal cell walls. To gain insight into the role of the GDSL gene family in suberin deposition and russet development in pear, we performed a genome-wide characterization of the GDSL family, including their identification, chromosomal localization, phylogenetic relationships, and expression patterns, in different tissues/organs in pear. One hundred and thirteen GDSL-type lipases/esterases genes were identified in the pear genome, and a phylogenetic analysis revealed that GDSL family can be classified into four distinct groups. Thirty GDSL genes were co-expressed with five homolog pear genes of three well-known suberin biosynthesis Arabidopsis genes (AtGPAT5, AtASFT, and AtCYP86B1) in the transcriptional co-expression network during pear fruit development. Among the 30 co-expressed GDSL genes, twelve genes were further analyzed by quantitative Real-time PCR, and the results showed the expression levels of the 12 genes were different between the russet exocarp and green exocarp of sand pear at different fruit development stages. Our study provides a detailed overview of the GDSL gene family and lays the foundation for future functional characterization of GDSL genes in P. bretschneideri.

Overexpression of OsCASP1 Improves Calcium Tolerance in Rice.

The Casparian strip domain protein 1 (OsCASP1) is necessary for the formation of the Casparian strip (CS) in the rice endodermis. It also controls Ca2+ transport to the stele. Here, we demonstrated that OsCASP1 overexpression enhanced Ca tolerance in rice. Under normal conditions, OsCASP1-overexpressed lines showed similar concentrations of essential metals in the roots and shoots compared to the wild type, while under high Ca conditions, Ca in the roots, shoots, and xylem sap of the OsCASP1-overexpressed lines was significantly decreased. This did not apply to other essential metals. Ca-inhibited growth was significantly alleviated in the OsCASP1-overexpressed lines. Furthermore, OsCASP1 overexpression resulted in earlier formation of both the CS and functional apoplastic barrier in the endodermis but did not induce ectopic CS formation in non-endodermal cell layers and affect suberin accumulation in the endodermis. These results indicate that the overexpression of OsCASP1 promotes CS formation in endodermal cells and inhibits Ca2+ transport by the apoplastic pathway, restricting Ca accumulation in the roots and shoots under high Ca conditions. Taken together, the results suggest that OsCASP1 overexpression is an effective way to improve rice adaptation to high Ca environments.

An integrated metabolic and transcriptomic analysis reveals the mechanism through which fruit bagging alleviates exocarp semi-russeting in pear fruit.

Fruit semi-russeting is an undesirable quality trait that occurs in fruit production. It is reported that preharvest fruit bagging could effectively alleviate fruit exocarp semi-russeting, but the physiological and molecular mechanisms remain unclear. In the present study, we performed an in-depth investigation into pear fruit semi-russeting from morphologic, metabolic and transcriptomic perspectives by comparing control (semi-russeted) and bagged (non-russeted) 'Cuiguan' pear fruits. The results showed that significant changes in cutin and suberin resulted in pear fruit semi-russeting. Compared with the skin of bagged fruits, the skin of the control fruits presented reduced cutin contents accompanied by an accumulation of suberin, which resulted in fruit semi-russeting; α, ω-dicarboxylic acids accounted for the largest proportion of typical suberin monomers. Moreover, combined transcriptomic and metabolic analysis revealed a series of genes involved in cutin and suberin biosynthesis, transport and polymerization differentially expressed between the two groups. Furthermore, the expression levels of genes involved in the stress response and in hormone biosynthesis and signaling were significantly altered in fruits with contrasting phenotypes. Finally, a number of transcription factors, including those of the MYB, NAC, bHLH and bZIP families, were differentially expressed. Taken together, the results suggest that the multilayered mechanism through which bagging alleviates pear fruit semi-russeting is complex, and the large number of candidate genes identified provides a good foundation for future functional studies.

Low calcium-induced delay in development of root apoplastic barriers enhances Cd uptake and accumulation in Sedum alfredii

Mineral nutrients play an important role in heavy metal uptake and accumulation in plant. However, the effects of calcium (Ca) supply level on apoplastic transport in roots and consequences for uptake of cadmium (Cd) in hyperaccumulators are poorly understood. Here, we investigated how Ca regulated the development of apoplastic barriers in the roots of two ecotypes of Sedum alfredii and assessed its effects on Cd uptake. Results of correlation analysis indicated that Ca content was positively correlated with the development of Casparian strips (CSs) and suberin lamellae (SL) in the absence or presence of Cd. Simultaneously, low Ca supply was proven to delay the formation of endodermis CSs and suberin accumulation by decreasing the relative expressions of genes associated with CSs localization and lignin/suberin synthesis. Moreover, Cd in apoplastic fluid and cell walls (regarding the apoplastic transport) and symplastic fractions were elevated by low Ca supply. Contrary to high Ca supply, the expression levels of genes related to Cd influx and xylem loading were increased upon low Ca addition in roots of both ecotypes. All the results above suggested that low Ca supply promotes root Cd uptake via apoplastic pathway by delaying apoplastic barriers development and also regulating Cd transport to the xylem in S. alfredii.

Preharvest multiple sprays with sodium nitroprusside promote wound healing of harvested muskmelons by activation of phenylpropanoid metabolism

Muskmelons are susceptible to mechanical damage at harvest and subsequent postharvest handling before storage. The wounds provide an easy pathway for fungi to infect, leading to postharvest decay of fruit during storage. Wound healing is considered as a positive defense process, which can restrict the invasion of pathogens. In this study, muskmelon fruit (Cucumis melo cv. Manao) during growth were repeatedly sprayed with 0.5 mM sodium nitroprusside (SNP, a exogenous donor of nitric oxide (NO)) or 0.1 mM 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO, a scavenger of NO), to test the effect of these preharvest treatments on wound healing of harvested muskmelon fruit. The results showed that SNP sprays reduced decay incidence and disease severity of harvested muskmelons inoculated with Trichothecium roseum. SNP also promoted the accumulation of suberin and lignin at wound sites through increasing phenylalanine ammonia lyase (PAL) activity and stimulating the accumulation in total phenolics, flavonoids and lignin. On the contrary, c-PTIO sprays enhanced decay incidence and disease severity of wounded inoculated fruit, while decreasing PAL activity, the content of total phenolics, flavonoids and lignin and reduced the accumulation of suberin and lignin at wound sites. The present results suggest that NO released by SNP sprays promote the wound healing and prevent disease development in harvested muskmelons by inducing increase in PAL activity, the contents of phenolics, flavonoids, suberin and lignin accumulation at wound sites.

Healing of Gladioulus grandiflora corms and Fusarium oxysporum infection

ABSTRACTGladiolus grandiflorus L. is highly susceptible to Fusarium and losses caused by this disease varies from 60% to 100%. Injuries caused during harvest, transport and inadequate storage, facilitate infection. The dynamics of wound healing can reduce infection by Fusarium. The objective was to characterize the wound healing in corms of G. grandiflora stored under refrigeration and how it affects the entry and establishment of F. oxysporum f. sp. gladioli infection. Corms were wounded and stored at 12 ± 4°C and relative humidity of 90 ± 5%. Cell damage, fresh weight loss, respiration, phenolic compounds, tissue darkening, suberization, lignification and resistance to infection were evaluated. Wounds on corms caused transepidermal damage with collapse and cell death. Physiological (increased loss of mass and respiration) and biochemical changes (deposition of lignin and suberin, enzymatic activity) occurred in the cells neighboring those death by the injury. The injury caused gradual darkening of the tissue, injured and neighbor. Fusarium oxysporum infection decreased with wound healing. The healing of injured G. grandiflora corms stored at 12ºC occurs from the 3rd day after injury by the accumulation of suberin, lignin, and melanin, inhibiting F. oxysporum f. sp. gladioli infection.

GbCYP86A1-1 from Gossypium barbadense positively regulates defence against Verticillium dahliae by cell wall modification and activation of immune pathways.

SummarySuberin acts as stress‐induced antipathogen barrier in the root cell wall. CYP86A1 encodes cytochrome P450 fatty acid ω‐hydroxylase, which has been reported to be a key enzyme for suberin biosynthesis; however, its role in resistance to fungi and the mechanisms related to immune responses remain unknown. Here, we identified a disease resistance‐related gene, GbCYP86A1‐1, from Gossypium barbadense cv. Hai7124. There were three homologs of GbCYP86A1 in cotton, which are specifically expressed in roots and induced by Verticillium dahliae. Among them, GbCYP86A1‐1 contributed the most significantly to resistance. Silencing of GbCYP86A1‐1 in Hai7124 resulted in severely compromised resistance to V. dahliae, while heterologous overexpression of GbCYP86A1‐1 in Arabidopsis improved tolerance. Tissue sections showed that the roots of GbCYP86A1‐1 transgenic Arabidopsis had more suberin accumulation and significantly higher C16‐C18 fatty acid content than control. Transcriptome analysis revealed that overexpression of GbCYP86A1‐1 not only affected lipid biosynthesis in roots, but also activated the disease‐resistant immune pathway; genes encoding the receptor‐like kinases (RLKs), receptor‐like proteins (RLPs), hormone‐related transcription factors, and pathogenesis‐related protein genes (PRs) were more highly expressed in the GbCYP86A1‐1 transgenic line than control. Furthermore, we found that when comparing V. dahliae ‐inoculated and noninoculated plants, few differential genes related to disease immunity were detected in the GbCYP86A1‐1 transgenic line; however, a large number of resistance genes were activated in the control. This study highlights the role of GbCYP86A1‐1 in the defence against fungi and its underlying molecular immune mechanisms in this process.

New insights of low-temperature plasma effects on germination of three genotypes of Arabidopsis thaliana seeds under osmotic and saline stresses

In order to investigate the effects of low temperature plasmas on germination of Arabidopsis thaliana seeds, a dielectric barrier discharge device generating the plasma in ambient air was used. To highlight the different plasma effects on the seed surface, saline and osmotic stresses were considered in the case of reference Col-0 seeds and two further seed coat mutants gl2 and gpat5 to better analyse the seed surface changes and their consequences on germination. The GL2 gene encode a transcription factor controlling the balance between the biosynthesis of fatty acids in the embryo and the production of mucilage and flavonoid pigments in the seed coat. The GPAT5 gene encode for an acyltransferase necessary for the accumulation of suberin in the seed coat which is essential for the embryo protection. The testa and endosperm ruptures are identified to note the germination stage. An increasing of germination rate, possibly due to the modification of mantle layers structure, is observed in most of cases, even in presence of saline or osmotic stress, after plasma treatment. Furthermore, we demonstrated that the germination rate of the gl2 mutant seeds is increased by at most 47% after plasma treatment, contrariwise, the germination of gpat5 mutant being initially lower is inhibited by the same plasma treatment. The scanning electron microscopy pictures and confocal microscopy fluorescence both showed changes of the exterior aspects of the seeds after plasma treatment. Considering these results, we assumed that lipid compounds can be found on the surface. To validate this hypothesis, permeability tests were performed, and it was clearly shown that a permeability decrease is induced by the low temperature plasma treatment.