Combined effects of micron-sized polyvinyl chloride particles and copper on seed germination of perilla.

Microplastics (MPs) and copper (Cu) pollution coexist widely in cultivation environment. In this paper, polyvinyl chloride (PVC) were used to simulate the MPs exposure environment, and the combined effects of MPs + Cu on the germination of perilla seeds were analyzed. The results showed that low concentrations of Cu promoted seed germination, while medium to high concentrations exhibited inhibition and deteriorated the morphology of germinated seeds. The germination potential, germination index and vitality index of 8 mg • L-1 Cu treatment group with were 23.08%, 76.32% and 65.65%, respectively, of the control group. The addition of low concentration PVC increased the above indicators by 1.27, 1.15, and 1.35 times, respectively, while high concentration addition led to a decrease of 65.38%, 82.5%, and 66.44%, respectively. The addition of low concentration PVC reduced the amount of PVC attached to radicle. There was no significant change in germination rate. PVC treatment alone had no significant effect on germination. MPs + Cu inhibited seed germination, which was mainly reflected in the deterioration of seed morphology. Cu significantly enhanced antioxidant enzyme activity, increased reactive oxygen species (ROS) and MDA content. The addition of low concentration PVC enhanced SOD activity, reduced MDA and H2O2 content. The SOD activity of the Cu2+8 + PVC10 group was 4.05 and 1.35 times higher than that of the control group and Cu treatment group at their peak, respectively. At this time, the CAT activity of the Cu2+8 + PVC5000 group increased by 2.66 and 1.42 times, and the H2O2 content was 2.02 times higher than the control. Most of the above indicators reached their peak at 24 h. The activity of α-amylase was inhibited by different treatments, but ß-amylase activity, starch and soluble sugar content did not change regularly. The research results can provide new ideas for evaluating the impact of MPs + Cu combined pollution on perilla and its potential ecological risk.

Effects of phosphite as a plant biostimulant on metabolism and stress response for better plant performance in Solanum tuberosum.

Food availability represents a major worldwide concern due to population growth, increased demand, and climate change. Therefore, it is imperative to identify compounds that can improve crop performance. Plant biostimulants have gained prominence because of their potentials to increase germination, productivity and quality of a wide range of horticultural and agronomic crops. Phosphite (Phi), an analog of orthophosphate, is an emerging biostimulant used in horticulture and agronomy. The aim of this study was to uncover the molecular mechanisms through which Phi acts as a biostimulant with potential effects of overall plant growth. Field and greenhouse experiments, using 4 potato cultivars, showed that following Phi applications, plant performance, including several physio-biochemical traits, crop productivity, and quality traits, were significantly improved. RNA sequencing of control and Phi-treated plants of cultivar Xingjia No. 2, at 0 h, 6 h, 24 h, 48 h, 72 h and 96 h after the Phi application for 24 h revealed extensive changes in the gene expression profiles. A total of 2856 differentially expressed genes were identified, suggesting that multiple pathways of primary and secondary metabolism, such as flavonoids biosynthesis, starch and sucrose metabolism, and phenylpropanoid biosynthesis, were strongly influenced by foliar applications of Phi. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses associated with defense responses revealed significant effects of Phi on a plethora of defense mechanisms. These results suggest that Phi acted as a biostimulant by priming the plants, that was, by triggering dynamic changes in gene expression and modulating metabolic fluxes in a way that allowed plants to perform better. Therefore, Phi usage has the potential to improve crop yield and health, alleviating the challenges posed by the need of feeding a growing world population, while minimizing the agricultural impact on human health and environment.

Physiological and transcriptomic responses of water spinach (Ipomoea aquatica) to prolonged heat stress.

BACKGROUND: Water spinach (Ipomoea aquatica) is an important heat-resistant leafy vegetable that can survive under long-time heat stress condition. However, the physiological characteristics and molecular changes in its response to heat stress are poorly understood. RESULTS: In this study the selected water spinach cultivars with different thermo resistance and their physiological response to heat stress were examined. Under prolonged heat stress, plant growth was inhibited in all tested cultivars. This inhibition was accompanied by the reduction of photosynthetic performance. The reactive oxygen species system in terms of superoxide and hydrogen peroxide contents, as well as antioxidant polyphenols, were evaluated. The results showed that prolonged heat stress caused reduced antioxidant capacity, but the role of antioxidant capacity in a prolonged thermotolerance was not predominant. Transcriptomic analysis of the water spinach subjected to heat stress revealed that 4145 transcripts were specifically expressed with 2420 up-regulated and 1725 down-regulated in heat-sensitive and heat-tolerant cultivars treated with 42 °C for 15 days. Enrichment analysis of these differentially expressed genes showed that the main metabolic differences between heat-sensitive and heat-tolerant cultivars were the carbohydrate metabolism and phenylpropanoid biosynthesis. The results of carbohydrate profiles and RT-qPCR also suggested that heat stress altered carbohydrate metabolism and associated changes in transcriptional level of genes involved in sugar transport and metabolic transition. CONCLUSIONS: The prolonged heat stress resulted in a reduced antioxidant capacity while the role of antioxidant capacity in a prolonged thermotolerance of water spinach was not predominant. Transcriptome analysis and the measurement of carbohydrates as well as the gene expression evaluation indicated that the response of the metabolic pathway such as carbohydrate and phenylpropanoid biosynthesis to heat stress may be a key player in thermo resistance.

Specific response mechanism to autotoxicity in melon (Cucumis melo L.) root revealed by physiological analyses combined with transcriptome profiling.

Melon is of great value in food, medicine and industry. In recent years, the continuous cropping obstacles of melon is increasingly prominent, which seriously affects the cultivation. Autotoxicity is the key factor for the obstacles. Root is the first line against autotoxicity and main organs for autotoxins secretion. Some physiological responses and differentially expressed genes (DEGs) related to autotoxicity are only limited to root system. Considering the lack of relevant research, physiological researches combined with transcriptome sequencing of melon seedling after autotoxicity stress mediated by root exudates (RE) was performed to help characterize the response mechanism to autotoxicity in melon roots. The results showed that autotoxicity inhibited root morphogenesis of melon seedlings, induced the excessive accumulation of reactive oxygen species (ROS) and lipid peroxidation in roots, and activated most antioxidant enzymes. Compared with the control group, the osmoregulation substance content was always at a high level. DEGs response to autotoxicity in roots were distinguished from that in leaves. Functional annotation of these DEGs suggested that autotoxicity affected biological regulation in a negative manner. DEGs were mainly involved in the synthesis of antioxidants, DNA damage and metabolism, and stress response. These setbacks were associated with the deterioration of root morphogenesis, generation of dwarf and slender roots, and ultimately leading to plant death. The results may provide important information for revealing the response mechanism of root to autotoxicity, and provide theoretical basis for solving the continuous cropping obstacles in melon.

Alleviating effect of silicon on melon seed germination under autotoxicity stress.

Melon (Cucumis melo L.) is an important horticultural crop worldwide. Continuous cropping obstacle occurs in many melon cultivation area, resulting in poor plant growth and fruit quality, autotoxicity is the main reason for the obstacle. Silicon (Si) plays an important role in improving the resistance of plants to biotic and abiotic stresses. In this study, melon plant water extracts (MPWE) were used to simulate the autotoxicity stress. Different concentrations of Na2SiO3 (0, 1, 2, 4, 8, 16, 32 mM) were added into MPWE for preliminary concentration screening and alleviating effect determination of Si on melon seed autotoxicity. The results showed that autotoxicity reduced the seed germination index, inhibited the growth of germinated seeds. 2 mM Si significantly increased seed germination index and improved subsequent growth under autotoxicity. The effect of Si showed a concentration-dependent manner, which can be counteracted or even reversed at high concentration. Three treatment combinations, double distilled water, 0.02 g/mL MPWE and 2 mM Na2SiO3 + 0.02 g/mL MPWE were used for subsequent physiology, biochemistry and gene analysis. During the germination of melon seed under autotoxicity, starch degradation ability decreased, amylase activity and amylase gene expression were inhibited, cell membrane lipid peroxidation increased, and antioxidant enzyme activity was abnormal. In Si-addition group, the radicle growth, lateral roots number, starch degradation ability, amylase activity and amylase gene expression level increased. The addition of Si also maintained the activities of superoxide dismutase, catalase and peroxidase and the content of malondialdehyde in a relatively normal state. The change trend of amylase gene and antioxidant enzyme activity was complex, but the acute change coincided with the key stage of seed germination, which occurred when the seed was about to break through or just broken through the seed coat. Appropriate concentration of Si is an effective strategy to alleviate the autotoxicity on melon seed.

Exogenous phosphite application alleviates the adverse effects of heat stress and improves thermotolerance of potato (Solanum tuberosum L.) seedlings.

Phosphite (Phi), an analog of phosphate (Pi) anion, is emerging as a potential biostimulator, fungicide and insecticide. Here, we reported that Phi also significantly enhanced thermotolerance in potatoes under heat stress. Potato plants with and without Phi pretreatment were exposed to heat stress and their heat tolerance was examined by assessing the morphological characteristics, photosynthetic pigment content, photosystem II (PS II) efficiency, levels of oxidative stress, and level of DNA damage. In addition, RNA-sequencing (RNA-Seq) was adopted to investigate the roles of Phi signals and the underlying heat resistance mechanism. RNA-Seq revealed that Phi orchestrated plant immune responses against heat stress by reprograming global gene expressions. Results from physiological data combined with RNA-Seq suggested that the supply of Phi not only was essential for the better plant performance, but also improved thermotolerance of the plants by alleviating oxidative stress and DNA damage, and improved biosynthesis of osmolytes and defense metabolites when exposed to unfavorable thermal conditions. This is the first study to explore the role of Phi in thermotolerance in plants, and the work can be applied to other crops under the challenging environment.

Comparative transcriptome analyses revealed different heat stress responses in high- and low-GS Brassica alboglabra sprouts.

BACKGROUND: Chinese kale (Brassica alboglabra) contains high nutritional elements and functional molecules, especially anticarcinogenic and antioxidant glucosinolates (GS), which was highly affected by environment temperature. To investigate the link of GS biosynthesis with heat stress response in Chinese kale, global transcription profiles of high-GS line (HG), low-GS line (LG), high-GS line under heat stress (HGT) and low-GS line under heat stress (LGT) were analyzed. RESULTS: Based on three biological replicates of each RNA sequencing data, 3901, 4062 and 2396 differentially expressed genes in HG vs HGT, LG vs LGT and HGT vs LGT were obtained, respectively. GO annotation, KEGG pathway analysis and a comprehensive analysis of DEGs showed a strong correlation between the GS biosynthesis and heat stress response. It was noticed that 11 differentially expressed genes tied to the GS biosynthesis were down-regulated, 23 heat shock transcription factors and 61 heat shock proteins were up-regulated upon the heat treatment. Another two Chinese kale varieties Cuibao and Shunbao with high- and low- GS content respectively, were used to validate the relationship of GS content and heat-response, and the results showed that high-GS content variety were more thermotolerant than the low-GS content one although GS significantly decreased in both varieties under heat stress. In addition, HSP100/ClpB, HSP90, HSP70 and sHSPs were differentially expressed in high- and low-GS varieties. Notably, HSP90 and sHSPs showed an obviously early response to heat stress than other related genes. CONCLUSION: The higher heat resistance of high-GS Chinese kale and the sharp decrease of glucosinolate content under heat stress indicated a strong relationship of GS accumulation and heat stress response. Combined with the previous report on the low expression of HSP90 at elevated temperatures in GS-deficient mutant TU8 of Arabidopsis, the differential expression pattern of HSP90 in high- and low- GS varieties and its early heat response implied it might be a key regulator in GS metabolism and heat-resistance in Chinese kale.

Translocation of phosphite encourages the protection against Phytophthora infestans in potato: The efficiency and efficacy.

Phosphite (Phi)-based fungicides, such as the commercial product Phostrol™, are widely used in potato late blight control. However, the Phi translocation efficiency and the efficacy against pathogen are less discussed. In this study, the Phi concentration were quantified by high performance ion chromatography (HPIC) and the Phi translocation efficiency in potato tissues was evaluated using potato cultivar Russet Burbank with foliar application of the Phostrol solution both under greenhouse and field conditions. In the greenhouse trials, it was found that Phi was translocated from leaves to roots within 3 h and its concentration was significantly increased in the roots 24 h after the Phostrol application. In the field trials, the application rate of Phostrol affected the Phi translocation in potato tubers. To assess the efficacy of Phi against P. infestans, both the inhibition and infection tests were carried out. In the inhibition tests, three most common strains of P. infestans in Canada (US-8, US-23 and US-24) were inoculated on pea agar containing different levels of Phi. In the infection tests, both of detached leaves and whole tubers that received Phi were infected by the three strains of P. infestans. The in vitro tests indicated that the US-8 strain is the most tolerant whereas the US-23 strain is the most sensitive to Phi. Also, the in vivo tests demonstrated the dose-dependent translocation of Phi in potato leaves and tubers decreased the severity of infection by P. infestans. Moreover, potential defense mechanisms related to salicylic acid (SA) and jasmonic acid (JA) pathways that might be activated by Phi were also explored. Overall, the results of the study provided evidences that high Phi translocation efficiency encouraged late blight suppression in potato production.

Root suberization in the response mechanism of melon to autotoxicity.

Continuous cropping obstacles poses significant challenges for melon cultivation, with autotoxicity being a primary inducer. Suberization of cells or tissues is a vital mechanism for plant stress response. Our study aimed to elucidate the potential mechanism of root suberization in melon's response to autotoxicity. Cinnamic acid was used to simulate autotoxicity. Results showed that autotoxicity worsened the root morphology and activity of seedlings. Significant reductions were observed in root length, diameter, surface area, volume and fork number compared to the control in the later stage of treatment, with a decrease ranging from 20% to 50%. The decrease in root activity ranged from 16.74% to 29.31%. Root suberization intensified, and peripheral suberin deposition became more prominent. Autotoxicity inhibited phenylalanineammonia-lyase activity, the decrease was 50% at 16 h. The effect of autotoxicity on cinnamylalcohol dehydrogenase and cinnamate 4-hydroxylase activity showed an initial increase followed by inhibition, resulting in reductions of 34.23% and 44.84% at 24 h, respectively. The peroxidase activity only significantly increased at 24 h, with an increase of 372%. Sixty-three differentially expressed genes (DEGs) associated with root suberization were identified, with KCS, HCT, and CYP family showing the highest gene abundance. GO annotated DEGs into nine categories, mainly related to binding and catalytic activity. DEGs were enriched in 27 KEGG pathways, particularly those involved in keratin, corkene, and wax biosynthesis. Seven proteins, including C4H, were centrally positioned within the protein interaction network. These findings provide insights for improving stress resistance in melons and breeding stress-tolerant varieties.

Physiological analysis and transcriptome profiling reveals the impact of microplastic on melon (Cucumis melo L.) seed germination and seedling growth.

The wide application of agricultural plastics leads to microplastic (MP) accumulation in the soil and inevitably result in MP pollution. Melon is an economically important horticultural crop that is widely cultivated with plastic film mulching. However, the impact of MP pollution on plant growth remains largely unclear. Here we reported the morphological, physiological, biochemical responses and transcriptome re-programing of melon responses to MP on seed germination and seedling growth. Polyvinyl chloride particles were added to potting mix to simulate MP exposure environment (MEE). The results showed that low and medium concentrations (1-4 g kg-1) of MEE had a significant adverse effect on seed germination and seedling growth. In both cases, the germination potential was decreased, young root forks increased, and tips decreased; and the dry weight of seedlings, the total length, surface area, forks and tips of root were also decreased. However, the root activity was increased. The concentration of MEE to give the best parameters was at 2 g kg-1. Catalase enzymatic activity and reactive oxygen species (ROS) in roots were decreased continuously with increased MEE concentrations. The peak values of peroxidase activity, O2.- content and generation rate, ROS enrichment and malondialdehyde content all reached the highest at 2 g kg-1. MEE also increased the proline content and decreased the contents of ascorbic acid, soluble sugar and soluble protein in these seedlings. Medium and high concentrations of MEE (4-8 g kg-1) also increased the chlorophyll b content. Low concentrations MEE (1-2 g kg-1) inhibited actual photochemical efficiency of photosystem II and photochemical quenching, two key chlorophyll fluorescence parameters. Transcriptome analysis showed that the differentially expressed genes caused by the MEE were mainly belonged to defense response, signal transduction, hormone metabolism, plant-pathogen interaction, and phenylpropanoid biosynthesis. The results of this study will help to understand the ecotoxicological effects of MEE on melons and provide data for ecological risk assessment of Cucurbitaceae vegetable cultivation.

The function of BoTCP25 in the regulation of leaf development of Chinese kale.

XG Chinese kale (Brassica oleracea cv. 'XiangGu') is a variety of Chinese kale and has metamorphic leaves attached to the true leaves. Metamorphic leaves are secondary leaves emerging from the veins of true leaves. However, it remains unknown how the formation of metamorphic leaves is regulated and whether it differs from normal leaves. BoTCP25 is differentially expressed in different parts of XG leaves and respond to auxin signals. To clarify the function of BoTCP25 in XG Chinese kale leaves, we overexpressed BoTCP25 in XG and Arabidopsis, and interestingly, its overexpression caused Chinese kale leaves to curl and changed the location of metamorphic leaves, whereas heterologous expression of BoTCP25 in Arabidopsis did not show metamorphic leaves, but only an increase in leaf number and leaf area. Further analysis of the expression of related genes in Chinese kale and Arabidopsis overexpressing BoTCP25 revealed that BoTCP25 could directly bind the promoter of BoNGA3, a transcription factor related to leaf development, and induce a significant expression of BoNGA3 in transgenic Chinese kale plants, whereas this induction of NGA3 did not occur in transgenic Arabidopsis. This suggests that the regulation of Chinese kale metamorphic leaves by BoTCP25 is dependent on a regulatory pathway or elements specific to XG and that this regulatory element may be repressed or absent from Arabidopsis. In addition, the expression of miR319's precursor, a negative regulator of BoTCP25, also differed in transgenic Chinese kale and Arabidopsis. miR319's transcrips were significantly up-regulated in transgenic Chinese kale mature leaves, while in transgenic Arabidopsis, the expression of miR319 in mature leaves was kept low. In conclusion, the differential expression of BoNGA3 and miR319 in the two species may be related to the exertion of BoTCP25 function, thus partially contributing to the differences in leaf phenotypes between overexpressed BoTCP25 in Arabidopsis and Chinese kale.

Protein profiling in potato (Solanum tuberosum L.) leaf tissues by differential centrifugation.

Foliar diseases, such as late blight, result in serious threats to potato production. As such, potato leaf tissue becomes an important substrate to study biological processes, such as plant defense responses to infection. Nonetheless, the potato leaf proteome remains poorly characterized. Here, we report protein profiling of potato leaf tissues using a modified differential centrifugation approach to separate the leaf tissues into cell wall and cytoplasmic fractions. This method helps to increase the number of identified proteins, including targeted putative cell wall proteins. The method allowed for the identification of 1484 nonredundant potato leaf proteins, of which 364 and 447 were reproducibly identified proteins in the cell wall and cytoplasmic fractions, respectively. Reproducibly identified proteins corresponded to over 70% of proteins identified in each replicate. A diverse range of proteins was identified based on their theoretical pI values, molecular masses, functional classification, and biological processes. Such a protein extraction method is effective for the establishment of a highly qualified proteome profile.

Aluminum in plant: Benefits, toxicity and tolerance mechanisms.

Aluminum (Al) is the third most ubiquitous metal in the earth's crust. A decrease in soil pH below 5 increases its solubility and availability. However, its impact on plants depends largely on concentration, exposure time, plant species, developmental age, and growing conditions. Although Al can be beneficial to plants by stimulating growth and mitigating biotic and abiotic stresses, it remains unknown how Al mediates these effects since its biological significance in cellular systems is still unidentified. Al is considered a major limiting factor restricting plant growth and productivity in acidic soils. It instigates a series of phytotoxic symptoms in several Al-sensitive crops with inhibition of root growth and restriction of water and nutrient uptake as the obvious symptoms. This review explores advances in Al benefits, toxicity and tolerance mechanisms employed by plants on acidic soils. These insights will provide directions and future prospects for potential crop improvement.

Irrigation Effect on Yield, Skin Blemishes, Phellem Formation, and Total Phenolics of Red Potatoes.

Dark Red Norland is an important potato cultivar in the fresh market due to its attractive bright, red colour, and good yield. However, skin blemishes such as silver patch, surface cracking, and russeting can negatively influence the tuber skin quality and marketability. It is well known that potato is a drought-sensitive plant. This study was conducted to determine whether irrigation would affect Dark Red Norland's yield and skin quality. A three-year field trial was conducted by Peak of the Market in Manitoba, Canada. Plants were treated under both irrigation and rainfed conditions. The results show that irrigation increased the total yield by 20.6% and reduced the severity of surface cracking by 48.5%. Microscopy imaging analysis demonstrated that tubers from the rainfed trials formed higher numbers of suberized cell layers than those of the irrigated potatoes, with a difference of 0.360 to 0.652 layers in normal skins. Surface cracking and silver patch skins had more suberized cell layers than the normal skins, with ranges of 7.805 to 8.333 and 7.740 to 8.496, respectively. A significantly higher amount of total polyphenols was found in the irrigated samples with a mean of 77.30 mg gallic acid equivalents (GAE)/100 g fresh weight (fw) than that of the rainfed samples (69.80 mg GAE/100 g fw). The outcome of this study provides a better understanding of the water regime effect causing these skin blemishes, which could potentially be used to establish strategies to improve tuber skin quality and minimize market losses.

Integration of Small RNA and Transcriptome Sequencing Reveal the Roles of miR395 and ATP Sulfurylase in Developing Seeds of Chinese Kale.

Seed development is closely related to plant production and reproduction, and MicroRNAs (miRNA) is widely involved in plant development including seed development. Chinese kale, as a Brassicaceae vegetable, mainly depends on seed for proper reproduction. In the present study, Chinese kale seed and silique at different stages were selected to establish small RNA (sRNA) libraries including silique wall sRNA libraries at torpedo-embryo stage (PC), silique wall sRNA libraries at cotyledonary-embryo stage (PD), seed sRNA libraries at torpedo-embryo stage (SC), and seed sRNA libraries at cotyledonary-embryo stage (SD). The results showed that miRNA expressed differentially in the seeds and corresponding siliques at different stages. To further clarify the functional mode of miRNA in the process of seed development, Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis was performed on target genes of the differentially expressed miRNAs, and these target genes were mainly enriched in plant hormone signal transduction, primary and secondary metabolic pathways. After joint analysis with the transcriptome change of the corresponding period, miR156-SPL10/SPL11, miR395-APS3, and miR397-LAC2/LAC11 modules were identified to be directly involved in the development of Chinese kale seeds. What's more, modified 5'RLM-RACE and Agrobacteria-mediated Chinese kale transient transformation suggest miR395b_2 is involved in sulfur metabolism during seed development by regulating its target gene APS3.

ROS and Oxidative Response Systems in Plants Under Biotic and Abiotic Stresses: Revisiting the Crucial Role of Phosphite Triggered Plants Defense Response.

Phosphite (Phi) is a chemical analog of orthophosphate [HPO4 3-]. It is a systemic pesticide generally known to control the prevalence of oomycetes and soil-borne diseases such as Phytophthora, Pythium, and Plasmopora species. Phi can also control disease symptoms and the spread of pathogenic bacteria, fungi, and nematodes. Phi plays critical roles as a fungicide, pesticide, fertilizer, or biostimulator. Overall, Phi can alleviate the severity of the disease caused by oomycete, fungi, pathogenic bacteria, and nematodes (leave, stem, fruit, tuber, and root) in various plants (vegetables, fruits, crops, root/tuber crops, ornamental plants, and forests). Advance research in molecular, physiological, and biochemical approaches has approved the key role of Phi in enhancing crop growth, quantity, and quality of several plant species. Phi is chemically similar to orthophosphate, and inside the cells, it is likely to get involved in different features of phosphate metabolism in both plants and pathogens. In plants, a range of physiobiochemical alterations are induced by plant pathogen stress, which causes lowered photosynthesis activities, enzymatic activities, increased accumulation of reactive oxygen species (ROS), and modification in a large group of genes. To date, several attempts have been made to study plant-pathogen interactions with the intent to minimize the loss of crop productivity. Phi's emerging function as a biostimulant in plants has boost plant yield and tolerance against various stress factors. This review discusses Phi-mediated biostimulant effects against biotic and abiotic stresses.

Relative quantitative proteomic analysis reveals wound response proteins correlated with after-cooking darkening.

Many common potato tuber defects are difficult to elucidate because of the degree of genetic complexity involved, making systems biology approaches necessary. Interaction between chlorogenic acid and iron is responsible for the darkening of potato tuber tissues upon heating--termed after-cooking darkening (ACD). To explore mechanisms of darkening severity in tuber tissues, we have employed relative quantitative proteomics to discover differentially expressed proteins involved in ACD. Tuber tissue samples were collected from a family of diploid clones which possess a highly segregated degree of the darkening. Exploiting this segregation, as well as the observation that darkening is more prevalent in the stem end of the tuber than the apical end, three sample groups were formed: (i) stem ends of three high-ACD clones, (ii) stem ends of three low-ACD clones, and (iii) apical ends of three low-ACD clones. Protein samples were digested and differentially labeled using isotopic reductive methylation, allowing for an orthogonal two-way comparison of protein profiles of the sample groups using 2-D-LC-MS/MS. Using a cutoff fold change of 2 between the high- and the low-ACD sample groups, 30 proteins showed a correlation with tissue darkening. Overall, we observed changes in relative protein abundance that showed an enhanced wound-response program in high-ACD tissues. Among these proteins, five proteins were further validated at the transcript level using qRT-PCR. These proteins may be incorporated into design strategies to create potato cultivars with low levels of ACD.

Genome-wide identification, characterization, and expression analysis related to autotoxicity of the GST gene family in Cucumis melo L.

Glutathione S-transferase (GST) plays an important role in plant resistance to biotic and abiotic stresses. In this paper, the characteristics of melon GST gene family members were analyzed from a genome-wide perspective. Forty-nine GSTs were identified in melon genome, belonging to eight classes. Through the phylogenetic analysis of GST proteins in melon and other plants, it was found that members from the same subfamily in different species clustered together, indicating that the subfamilies of GST have diversified before the divergence within these species. The results of chromosome mapping showed that GSTs were present in all chromosomes except for chromosome 5. Gene replication events played an important role in the expansion and evolution of melon GST gene family. Ten GSTs with significant differential expression were screened in the transcriptome database related to melon autotoxicity stress. The differential expression of these 10 GSTs was detected in roots and leaves of melon seedlings treated with cinnamic acid. The relative expression level of CmGSTU7, CmGSTU10, CmGSTU18, CmGSTF2 and CmGSTL1 in roots of melon seedlings was significantly higher than that in control group. It suggested that the five GSTs might play an important role in cinnamic acid mediated autotoxicity stress in melon. The results of this paper were helpful to reveal the evolution and functional succession of GST family and further understand the response of GST to autotoxicity stress in melon.

Phosphite Application Alleviates Pythophthora infestans by Modulation of Photosynthetic and Physio-Biochemical Metabolites in Potato Leaves.

Potato late blight (Phytophtora infestans) is among the most severely damaging diseases of potato (Solanum tuberusom L.) worldwide, causing serious damages in potato leaves and tubers. In the present study, the effects of potassium phosphite (KPhi) applications on photosynthetic parameters, enzymatic and non-enzymatic antioxidant properties, hydrogen peroxide (H2O2) and malondialdehyde (MDA), total protein and total carbohydrate of potato leaves challenged with P. infestans pathogen were investigated. Potato leaves were sprayed five times with KPhi (0.5%) during the growing season prior to inoculation with P. infestans. The potato leaves were artificially infected by the LC06-44 pathogen isolate. The leaves were sampled at 0, 24, 48, 72 and 96 h after the infection for evaluations. P. infestans infection reduced chlorophyll (Chl) pigments contents, chlorophyll fluorescence, carotenoid (Car) and anthocyanin contents and increased the accumulation of H2O2 and MDA. Meanwhile, our result showed that KPhi treatment alleviated adverse effect of late blight in potato leaves. KPhi application also increased plant tolerance to the pathogen with improved photosynthetic parameters Chl a, b, total Chl, Car, and anthocyanin compare to controls. Moreover, the increased oxidative enzymes activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APx), and non-enzymatic substances such as phenolics, flavonoids and proline were found in KPhi treated plants, compared to untreated plants after inoculation. In addition, KPhi application followed by P. infestans infection also decreased the content of H2O2 and MDA, but increased the total protein and total carbohydrate contents in potato leaves. The consequence of current research indicated that KPhi played a vital role in pathogen tolerance, protecting the functions of photosynthetic apparatus by improved oxidative levels and physio-biochemical compounds in potato leaves.

Effect of Photoperiod on Chinese Kale (Brassica alboglabra) Sprouts Under White or Combined Red and Blue Light.

To determine the response of Chinese kale (Brassica alboglabra) sprouts to photoperiods under different light sources, we used four photoperiods (0-h light/24-h dark, 8-h light/16-h dark, 12-h light/12-h dark, and 16-h light/8-h dark) to investigate their sprout growth and secondary metabolite glucosinolates (GSs) accumulation under white or combined red-and-blue (RB) light sources. We found that the 16-h light condition under RB light produced plants with the greatest dry matter. Sprouts grown under 16-h RB light condition achieved greater length than those under white light. To investigate the role of RB light in plant growth and GS accumulation, we applied RB light sources with different RB ratios (0:10, 2:8, 5:5, 8:2, and 10:0) to cultivate sprouts. The results showed that significant differential accumulation of GSs existed between sprouts grown under blue (RB, 0:10) and red (RB, 10:0) light; there was greater GS content under blue light. The underlying mechanism of differential GS content in sprouts under red or blue light condition was studied using RNA sequencing technique. Interestingly, abundant GS biosynthetic gene transcripts were observed in sprouts grown under red light compared with under blue light. The expression of ß-glucosidase family homolog genes related to GS degradation differed under red and blue light conditions, among those TGG4 homolog was detected with higher expression under red light than with blue light. Taking into consideration, the lower GS accumulation in sprouts under red rather than blue light, we conclude that the degradation of GSs may play a key role in sprouts GS homeostasis.