Jiping Sheng

Ethylene and cold participate in the regulation of LeCBF1 gene expression in postharvest tomato fruits

C‐Repeat/dehydration‐responsive element binding factor (CBF) is a transcription factor regulating cold response in plants, of which little is known in fruits. We showed a double‐peak expression pattern of Lycopersicon esculentum putative transcriptional activator CBF1 (LeCBF1) in mature green fruit. The peaks appeared at 2 and 16 h after subjection to cold storage (2 °C). The second peak was coincident with, and thus caused by a peak in endogenous ethylene production. We showed that LeCBF1 expression was regulated by exogenous ethylene and 1‐methylcyclopropene, and was not expressed without cold induction. LeCBF1 expression was different in the five maturation stages of fruits, but expression peaked at 2 h at all stages.

Methyl Salicylate-Induced Arginine Catabolism Is Associated with Up-regulation of Polyamine and Nitric Oxide Levels and Improves Chilling Tolerance in Cherry Tomato Fruit

The effects of methyl salicylate (MeSA) on chilling injury (CI) and gene expression levels, enzyme activities, and metabolites related to arginine catabolism in cherry tomato fruit were investigated. Freshly harvested fruits were treated with 0.05 mM MeSA vapor at 20 °C for 12 h and then stored at 2 °C for up to 28 days. MeSA reduced CI and enhanced the accumulation of putrescine, spermidine, and spermine, which was associated with increased gene expression levels and activities of arginase, arginine decarboxylase, and ornithine decarboxylase at most sampling times. MeSA also increased nitric oxide synthase activity, which at least partly contributed to the increased nitric oxide content. The results indicate that MeSA activates the different pathways of arginine catabolism in cold-stored fruit and that the reduction in CI by MeSA may be due to the coordinated metabolism of arginine and the increase in polyamines and nitric oxide levels.

Up-regulating arginase contributes to amelioration of chilling stress and the antioxidant system in cherry tomato fruits

BACKGROUND Arginase, which plays an important role in regulating the metabolism of L-arginine (Arg) in mammalian cells, has been reported to be involved in stress responses in higher plants. In view of the well-established roles of polyamines, nitric oxide and proline in plant tolerance to chilling stress, arginase may play an important role in fruit chilling tolerance by regulating the metabolism of Arg. However, the current information available on this is very limited. RESULTS Cherry tomatoes (Lycopersicon esculentum cv.Messina) at the mature green stage were treated with Arg or N(ω)--hydroxy-nor-L-arginine (nor-NOHA) and analysed for chilling injury, electrolyte leakage, malondialdehyde and proline contents and arginase and antioxidant enzyme (superoxide dismutase, catalase, peroxidaseand ascorbate peroxidase) activities during cold storage. The effects of low temperature on the transcriptional levels of two arginase genes (LeARG1 and LeARG2) were also evaluated. LeARG1 and LeARG2 expression and arginase activity were significantly induced by low temperature. Compared with the control, Arg treatment alleviated fruit chilling injury, reduced electrolyte leakage, malondialdehyde content and peroxidaseactivity and increased other parameters. Treatment with nor-NOHA caused the opposite effects. CONCLUSION Up-regulation of arginase activity and gene expression may be a chilling tolerance strategy in cherry tomato fruit. Inhibition of chilling-induced arginase activity could aggravate chilling injury and oxidation damage. Arginase appears to play an important role in the chilling resistance process of cherry tomato fruit induced by Arg.

Preharvest L-arginine treatment induced postharvest disease resistance to Botrysis cinerea in tomato fruits.

L-arginine is the precursor of nitric oxide (NO). In order to examine the influence of L-arginine on tomato fruit resistance, preharvest green mature tomato fruits (Solanum lycopersicum cv. No. 4 Zhongshu) were treated with 0.5, 1, and 5 mM L-arginine. The reduced lesion size (in diameter) on fruit caused by Botrytis cinerea, as well as activities of phenylalanine ammonia-lyase (PAL), Chitinase (CHI), β-1,3-glucanase (GLU), and polyphenoloxidase (PPO), was compared between L-arginine treated fruits and untreated fruits. We found that induced resistance increased and reached the highest level at 3-6 days after treatment. Endogenous NO concentrations were positively correlated with PAL, PPO, CHI, and GLU activities after treatment with Pearson coefficients of 0.71, 0.94, 0.97, and 0.87, respectively. These results indicate that arginine induces disease resistance via its effects on NO biosynthesis and defensive enzyme activity.

Postharvest Application of Methyl Jasmonate for Improving Quality Retention of Agaricus bisporus Fruit Bodies

The influence of methyl jasmonate (MeJA) on postharvest quality and enzyme activities, gene expression level, and the functional component content linked to postharvest deterioration in Agaricus bisporus (J.E. Lange) Imbach fruit bodies was investigated. Freshly harvested fruit bodies were treated with 0 (control), 10 and 100 μM MeJA vapor at 20 °C for 12 h and then stored at 10 °C for up to 7 days. The results indicated that treatments with 100 μM MeJA vapor maintained a high level of soluble protein and total sugar, delayed browning, promoted the accumulation of phenolics and flavonoids, and inhibited the increase of respiratory rate and membrane leakage. Furthermore, 100 μM MeJA inhibited the activities of polyphenoloxidase, increased the antioxidant enzymes activities of catalase and superoxide dismutase, and lowered relative expression levels of three genes encoding polyphenol oxidase (AbPPO1, AbPPO2, and AbPPO3) throughout the storage period. Comparatively, 10 μM MeJA also had a clear beneficial effect on postharvest mushroom quality maintenance but was not as effective as 100 μM MeJA treatment. These findings suggest that application of MeJA could have potential in maintaining the quality of harvested A. bisporus fruit bodies.

Hot air treatment-induced arginine catabolism is associated with elevated polyamines and proline levels and alleviates chilling injury in postharvest tomato fruit

BACKGROUND To understand whether arginine catabolism might be involved in hot air (HA)-induced chilling tolerance mechanism in tomato fruit, we investigated the effect of HA treatment on endogenous arginine catabolism in relation to chilling injury. RESULTS Tomato fruit were harvested at mature green stage and treated with HA at 38°C for 12 h and then stored at 2°C for 21 days. The effects of HA treatment on fruit chilling injury and gene expression levels or enzyme activity, and metabolites related to arginine catabolism were evaluated. HA treatment reduced the chilling injury symptoms of tomato fruit and enhanced the accumulation of endogenous polyamines, especially putrescine and proline. This accumulation is associated with the increased transcript levels of genes encoding arginase (LeARG1 and LeARG2), arginine decarboxylase (LeADC), ornithine decarboxylase (LeODC) and ornithine aminotransferase (LeOAT) at most sampling times. However, HA treatment had little effect on nitric oxide synthase activity and nitric oxide concentration. CONCLUSION These results revealed that the reduction in chilling injury by HA treatment may be due to the accumulation of putrescine and proline induced primarily by activating the catabolism of endogenous arginine.

Novel Xylanase from a Holstein Cattle Rumen Metagenomic Library and Its Application in Xylooligosaccharide and Ferulic Acid Production from Wheat Straw

A novel gene fragment containing a xylanase was identified from a Holstein cattle rumen metagenomic library. The novel xylanase (Xyln-SH1) belonged to the glycoside hydrolase family 10 (GH10) and exhibited a maximum of 44% identity to the glycoside hydrolase from Clostridium thermocellum ATCC 27405. Xyln-SH1 was heterologously expressed, purified, and characterized. A high level of activity was obtained under the optimum conditions of pH 6.5 and 40 °C. A substrate utilization study indicated that Xyln-SH1 was cellulase-free and strictly specific to xylan from softwood. The synergistic effects of Xyln-SH1 and feruloyl esterase (FAE-SH1) were observed for the release of xylooligosaccharides (XOS) and ferulic acid (FA) from wheat straw. In addition, a high dose of Xyln-SH1 alone was observed to improve the release of FA from wheat straw. These features suggest that this enzyme has substantial potential to improve biomass degradation and industrial applications.

A protease-insensitive feruloyl esterase from China Holstein cow rumen metagenomic library: expression, characterization, and utilization in ferulic acid release from wheat straw.

A metagenomic library of China Holstein cow rumen microbes was constructed and screened for novel gene cluster. A novel feruloyl esterase (FAE) gene was identified with a length of 789 bp and encoded a protein displaying 56% identity to known esterase sequences. The gene was functionally expressed in Escherichia coli BL21 (DE3), and the total molecular weight of the recombined protein was 32.4 kDa. The purified enzyme showed a broad specificity against the four methyl esters of hydroxycinnamic acids and high activity (259.5 U/mg) to methyl ferulate at optimum conditions (pH 8.0, 40 °C). High thermal and pH stability were also observed. Moreover, the enzyme showed broad resistance to proteases. FAE-SH1 can enhance the release of ferulic acid from wheat straw with cellulase, β-1,4-endoxylanase, β-1,3-glucanase, and pectase. These features suggest FAE-SH1 as a good candidate to enhance biomass degradation and improve the health effects of food and forage.

LeMAPK1, LeMAPK2, and LeMAPK3 Are Associated with Nitric Oxide-Induced Defense Response against Botrytis cinerea in the Lycopersicon esculentum Fruit

Nitric oxide (NO) and mitogen-activated protein kinases (MAPKs) are signal molecules involved in the disease resistance of plants. To investigate the role of tomato MAPKs in the NO-mediated defense response, mature green tomatoes (Lycopersicon esculentum Mill. cv. Qian-xi) were treated with a MAPKs inhibitor (1,4-diamino-2,3-dicyano-1,4-bis(o-amino-phenylmercapto) butadiene (U0126)), NO donor sodium nitroprusside (SNP), and SNP plus U0126. Treatment with U0126 increased the incidence of disease and size of lesion areas in the tomato fruits after being inoculated with Botrytis cinerea. NO enhanced the resistance of the tomato fruits against Botrytis cinerea invasion and the activities of nitric oxide synthase, Chitinase, β-1,3-glucanase, polyphenol oxidase, and phenylalanine ammonia-lyase. However, the effects of NO on disease resistance were weakened by the MAPKs inhibitor. Meanwhile, the relative expression of LeMAPK1, LeMAPK2, and LeMAPK3 in the (SNP + U0126)-treated fruits was lower than that in the SNP-treated fruits. The results suggest that LeMAPK1/2/3 are involved in NO-induced disease resistance of tomato fruits against Botrytis cinerea.

Biocontrol Activity of Bacillus subtilis Isolated from Agaricus bisporus Mushroom Compost Against Pathogenic Fungi.

Bacillus subtilis strain B154, isolated from Agaricus bisporus mushroom compost infected by red bread mold, exhibited antagonistic activities against Neurospora sitophila. Antifungal activity against phytopathogenic fungi was also observed. The maximum antifungal activity was reached during the stationary phase. This antifungal activity was stable over a wide pH and temperature range and was not affected by proteases. Assay of antifungal activity in vitro indicated that a purified antifungal substance could strongly inhibit mycelia growth and spore germination of N. sitophila. In addition, treatment with strain B154 in A. bisporus mushroom compost infected with N. sitophila significantly increased the yield of bisporus mushrooms. Ultraviolet scan spectroscopy, tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis, matrix-associated laser desorption ionization time-of-flight mass spectrometry, and electrospray ionization tandem mass spectrometry analyses revealed a molecular weight consistent with 1498.7633 Da. The antifungal compound might belong to a new type of lipopeptide fengycin.