Cloning and characterization of a chitinase gene Lbchi31 from Limonium bicolor and identification of its biological activity

Study of the physiological mechanism of delaying cucumber senescence by wheat intercropping pattern

This paper investigates the physiological mechanism of the effect of delaying cucumber senescence on protein levels under the experimental model of monoculture and wheat intercropping. We analyzed cucumber roots for differential protein expression, and protein types were identified by core technology of proteomics. 45 differential proteins were identified as being differentially expressed between monoculture and intercropping of wheat, which were involved in carbohydrate metabolism, antioxidant and stress response, growth and development regulation, biological information transfer, and nucleic acid biosynthesis. The results showed the rate of photosynthesis of cucumber was increased under wheat intercropping pattern due to three enzymes being up-regulated. The respiration of cucumber was reduced when five enzymes were down-regulated. The antioxidant and resistant capacity of cucumber was enhanced significantly under wheat intercropping pattern because two enzymes were down-regulated while the activity of four other antioxidant enzymes was up-regulated. Intercropping wheat could delay the senescence of cucumber leaves by increasing the expression of IPT gene, reducing the expression of PAO and ETR2 gene, and inhibiting the expression of Cu/Zn-SOD and GS1 gene in later stages. Two proteins related to growth and development in cucumber were up-regulated, and one was down-regulated, while two proteins related to nucleic acid biosynthesis and chaperonin showed obvious down-regulation under wheat intercropping. Therefore, the growth and development was improved and senescence of cucumber could be delayed. Under intercropping pattern, the fresh weight, chlorophyll content, photosynthetic rate, and peroxidase activity of cucumber plants were higher than those of cucumber monoculture groups. Thus, the senescence of cucumber could be delayed under wheat intercropping by regulating its physiological mechanisms, such as by improving photosynthesis, reducing respiratory consumption, slowing the cell apoptosis rate, and enhancing the antioxidant and resistant capacity significantly, etc.

Cloning, Expression and 3D Structure Prediction of Chitinase from Chitinolyticbacter meiyuanensis SYBC-H1

Two CHI genes from Chitinolyticbactermeiyuanensis SYBC-H1 encoding chitinases were identified and their protein 3D structures were predicted. According to the amino acid sequence alignment, CHI1 gene encoding 166 aa had a structural domain similar to the GH18 type II chitinase, and CHI2 gene encoding 383 aa had the same catalytic domain as the glycoside hydrolase family 19 chitinase. In this study, CHI2 chitinase were expressed in Escherichia coli BL21 cells, and this protein was purified by ammonium sulfate precipitation, DEAE-cellulose, and Sephadex G-100 chromatography. Optimal activity of CHI2 chitinase occurred at a temperature of 40 °C and a pH of 6.5. The presence of metal ions Fe³⁺, Fe²⁺, and Zn²⁺ inhibited CHI2 chitinase activity, while Na⁺ and K⁺ promoted its activity. Furthermore, the presence of EGTA, EDTA, and β-mercaptoethanol significantly increased the stability of CHI2 chitinase. The CHI2 chitinase was active with p-NP-GlcNAc, with the K_m and V_m values of 23.0 µmol/L and 9.1 mM/min at a temperature of 37 °C, respectively. Additionally, the CHI2 chitinase was characterized as an N-acetyl glucosaminidase based on the hydrolysate from chitin. Overall, our results demonstrated CHI2 chitinase with remarkable biochemical properties is suitable for bioconversion of chitin waste.

Chitinase genes LbCHI31 and LbCHI32 from Limonium bicolor were successfully expressed in Escherichia coli and exhibit recombinant chitinase activities

The two chitinase genes, LbCHI31 and LbCHI32 from Limonium bicolor, were, respectively, expressed in Escherichia coli BL21 strain. The intracellular recombinant chitinases, inrCHI31 and inrCHI32, and the extracellular exrCHI31 and exrCHI32 could be produced into E. coli. The exrCHI31 and exrCHI32 can be secreted into extracellular medium. The optimal reaction condition for inrCHI31 was 5 mmol/L of Mn²⁺ at 40°C and pH 5.0 with an activity of 0.772 U using Alternaria alternata cell wall as substrate. The optimal condition of inrCHI32 was 5 mmol/L of Ba²⁺ at 45°C and pH 5.0 with an activity of 0.792 U using Valsa sordida cell wall as substrate. The optimal reaction condition of exrCHI31 was 5 mmol/L of Zn²⁺ at 40°C and pH 5.0, and the activity was 0.921 U using the A. alternata cell wall as substrate. Simultaneously, the optimal condition of exrCHI32 was 5 mmol/L of K⁺ at 45°C and pH 5.0, with V. sordida cell wall as the substrate, and the activity was 0.897 U. Furthermore, the activities of extracellular recombinant enzymes on fungal cell walls and compounds were generally higher than those of the intracellular recombinant enzymes. Recombinant exrCHI31 and exrCHI32 have better hydrolytic ability on cell walls of different fungi than synthetic chitins and obviously showed activity against A. alternata.

Overexpression of a heat shock protein (ThHSP18.3) from Tamarix hispida confers stress tolerance to yeast

It is well known that plant heat shock proteins (HSPs) play important roles both in response to adverse environmental conditions and in various developmental processes. However, among plant HSPs, the functions of tree plant HSPs are poorly characterized. To improve our understanding of tree HSPs, we cloned and characterized an HSP gene (ThHSP18.3) from Tamarix hispida. Sequence alignment reveals that ThHSP18.3 belongs to the class I small heat shock protein family. A transient expression assay showed that ThHSP18.3 protein was targeted to the cell nucleus. Treatment of Tamarix hispida with cold and heat shock highly induced ThHSP18.3 expression in all studied leaves, roots and stems, whereas, treatment of T. hispida with NaCl, NaHCO(3), and PEG induced ThHSP18.3 expression in leaves and decreased its expression in roots and stems. Further, to study the role of ThHSP18.3 in stress tolerance under different stress conditions, we cloned ThHSP18.3 into the pYES2 vector, transformed and expressed the vector in yeast Saccharomyces cerevisiae. Yeast cells transformed with an empty pYES2 vector were employed as a control. Compared to the control, yeast cells expressing ThHSP18.3 showed greater tolerance to salt, drought, heavy metals, and both low and high temperatures, indicating that ThHSP18.3 confers tolerance to these stress conditions. These results suggested that ThHSP18.3 is involved in tolerance to a variety of stress conditions in T. hispida.

Expression, characterization and 2,4,6-trichlorophenol degradation of laccase from Monilinia fructigena

A novel laccase gene from Monilinia fructigena was synthesized chemically according to the yeast bias codon and integrated into the genome of Pichia pastoris GS115 by electroporation. The expressed enzyme was recovered from the culture supernatant and purified. The result of enzyme activity assay and SDS-PAGE demonstrated that the recombinant laccase was induced and extracellularly expressed in P. pastoris. Main biochemical properties of this laccase, such as thermodependence and thermostability, optimal pH and pH stability, and the effect of metal ions and inhibitors, were characterized. With 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate (ABTS) as the substrate, MfLcc had its optimal pH at 3.5 and optimal temperature at 45°C. The Km values of the ABTS, guaiacol were 0.012 and 0.016 Mm, respectively, and the corresponding V (max) values are 243.9 and 10.55 Um min(-1) mg(-1), respectively. The recombinant laccase degraded 80% 2,4,6-trichlorophenol after 8 h under the optimal conditions. The recombinant strain and its laccase can be considered as candidate for treating waste water polluted with trichlorophenols.