Cloning and immunolocalization of an antifungal chitinase in jelly fig (Ficus awkeotsang) achenes

Characterization of a Chitosanase from Jelly Fig (Ficus awkeotsang Makino) Latex and Its Application in the Production of Water-Soluble Low Molecular Weight Chitosans

A chitosanase was purified from jelly fig latex by ammonium sulfate fractionation (50–80% saturation) and three successive column chromatography steps. The purified enzyme was almost homogeneous, as determined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and gel activity staining. The molecular mass of the enzyme was 20.5 kDa. The isoelectric point (pI) was <3.5, as estimated by isoelectric focusing electrophoresis on PhastGel IEF 3-9. Using chitosan as the substrate, the optimal pH for the enzyme reaction was 4.5; the kinetic parameters K_m and V_max were 0.089 mg mL^-1 and 0.69 μmol min^-1 mg^-1, respectively. The enzyme showed activity toward chitosan polymers which exhibited various degrees of deacetylation (21–94%). The enzyme hydrolyzed 70–84% deacetylated chitosan polymers most effectively. Substrate specificity analysis indicated that the enzyme catalyzed the hydrolysis of chitin and chitosan polymers and their derivatives. The products of the hydrolysis of chitosan polymer derivatives, ethylene glycol (EG) chitosan, carboxymethyl (CM) chitosan and aminoethyl (AE) chitosan, were low molecular weight chitosans (LMWCs); these products were referred to as EG-LMWC, CM-LMWC and AE-LMWC, respectively. The average molecular weights of EG-LMWC, CM-LMWC and AE-LMWC were 11.2, 11.2 and 8.89 kDa, respectively. All of the LMWC products exhibited free radical scavenging activities toward ABTS^•+, superoxide and peroxyl radicals.

Identification and characterization of a novel chitinase with antifungal activity from 'Baozhu' pear (Pyrus ussuriensis Maxim.)

A novel chitinase from the 'Baozhu' pear was found, purified, and characterized in this report. This chitinase was a monomer with a molecular mass of 28.9 kDa. Results of the internal peptide sequence analyses classify this chitinase as a class III chitinase. In the enzymatic hydrolytic assay, this chitinase could hydrolyze chitin derivatives into di-N-acetylchitobiose (GlcNAc2) as a major product in the initial phase, as well as hydrolyze GlcNAc2 into N-acetylglucosamine (GlcNAc), which represents both chitobiosidase and β-N-acetylglucosaminase activity. Biological analyses showed that this chitinase exhibits strong antifungal activity toward agricultural pathogenic fungi. In total, chitinase from 'Baozhu' pear is a novel bifunctional chitinase that could be a potential fungicide in the biological control of plant diseases.

Cloning and expression of pathogenesis-related protein 4 from jelly fig (Ficus awkeotsang Makino) achenes associated with ribonuclease, chitinase and anti-fungal activities

A cDNA fragment (FaPR4) encoding a class I pathogenesis-related protein 4 (PR-4) from Ficus awkeotsang was obtained by PCR cloning. Plant PR-4s were grouped into class I and II, differing by the presence of ChtBD and hinge. The predicted mature FaPR4 comprises N-terminal chitin-binding domain (ChtBD), hinge, Barwin domain and C-terminal extension. FaPR4-C, an N-terminal truncated form of FaPR4, was designed to mimic the structural feature of class II PR-4s. FaPR4 and FaPR4-C were over-expressed in yeast Pichia pastoris, and both recombinants exhibited RNase and anti-fungal activities. To our knowledge, it is the first report that FaPR4, a member of class I PR-4s has RNase activity as class II. FaPR4 possesses better anti-fungal activities toward Fusarium oxysporum and Sclerotium rolfsii than FaPR4-C. Heat-treated FaPR4 remained RNase and anti-fungal activities; while heat-treated FaPR4-C lost those activities. Therefore, ChtBD of FaPR4 may not only contribute to its anti-fungal but also improve the thermal stability of protein. It also implied the correlation of RNase activity with anti-fungal activity of FaPR4-C. Furthermore, FaPR4 was detected to have weak but significant chitinase activity, and its chitinase activity was reduced after heat treatment. The chitinase activity by FaPR4-C was much lower than FaPR4.

Cloning and characterization of an antifungal class III chitinase from suspension-cultured bamboo ( Bambusa oldhamii ) cells

A class III chitinase cDNA (BoChi3-1) was cloned using a cDNA library from suspension-cultured bamboo ( Bambusa oldhamii ) cells and then transformed into yeast ( Pichia pastoris X-33) for expression. Two recombinant chitinases with molecular masses of 28.3 and 35.7 kDa, respectively, were purified from the yeast's culture broth to electrophoretic homogeneity using sequential ammonium sulfate fractionation, Phenyl-Sepharose hydrophobic interaction chromatography, and Con A-Sepharose chromatography steps. N-Terminal sequencing and immunoblotting revealed that both recombinant chitinases were encoded by BoChi3-1, whereas SDS-PAGE and glycoprotein staining showed that the 35.7 kDa isoform (35.7 kDa BoCHI3-1) was glycosylated and the 28.3 kDa isoform (28.3 kDa BoCHI3-1) was not. For hydrolysis of ethylene glycol chitin (EGC), the optimal pH values were 3 and 4 for 35.7 and 28.3 kDa BoCHI3-1, respectively; the optimal temperatures were 80 and 70 degrees C, and the K(m) values were 1.35 and 0.65 mg/mL. The purified 35.7 kDa BoCHI3-1 hydrolyzed EGC more efficiently than the 28.3 kDa isoform, as compared with their specific activity and activation energy. Both recombinant BoCHI3-1 isoforms showed antifungal activity against Scolecobasidium longiphorum and displayed remarkable thermal (up to 70 degrees C) and storage (up to a year at 4 degrees C) stabilities.

Characterization of oil bodies in jelly fig achenes

Thin-layer chromatography analysis revealed that the contents stored in oil bodies isolated from jelly fig (Ficus awkeotsang Makino) achenes were mainly neutral lipids (>90% triacylglycerols and approximately 5% diacylglycerols). Fatty acids released from the neutral lipids of achene oil bodies were highly unsaturated (62.65% alpha-linolenic acid, 18.24% linoleic acid, and 10.62% oleic acid). The integrity of isolated oil bodies was presumably maintained via electronegative repulsion and steric hindrance provided by their surface proteins. Immunological cross-recognition using antibodies against sesame oil-body proteins indicated that two oleosin isoforms and one caleosin were present in these oil bodies. MALDI-MS analyses confirmed that the three full-length cDNA fragments obtained by PCR cloning from maturing achenes encoded the two jelly fig oleosin isoforms and one caleosin identified by immunological screening.

Heterologous expression of new antifungal chitinase from wheat

Chitinases (EC 3.2.1.14) have been grouped into seven classes (class I-VII) on the basis of their structural properties. Chitinases expressed during plant-microbe interaction are involved in defense responses of host plant against pathogens. In the present investigation, chitinase gene from wheat has been subcloned and overexpressed in Escherichia coli BL-21 (DE3). Molecular phylogeny analyses of wheat chitinase indicated that it belongs to an acidic form of class VII chitinase (glycosyl hydrolase family 19) and shows 77% identity with other wheat chitinase of class IV and low level identity to other plant chitinases. The three-dimensional structural model of wheat chitinase showed the presence of 10 alpha-helices, 3 beta-strands, 21 loop turns and the presence of 6 cysteine residues that are responsible for the formation of 3 disulphide bridges. The active site residues (Glu94 and Glu103) may be suggested for its antifungal activity. Expression of chitinase (33 kDa) was confirmed by SDS-PAGE and Western hybridization analyses. The yield of purified chitinase was 20 mg/L with chitinase activity of 1.9 U/mg. Purified chitinase exerted a broad-spectrum antifungal activity against Colletotrichum falcatum (red rot of sugarcane) Pestalotia theae (leaf spot of tea), Rhizoctonia solani (sheath blight of rice), Sarocladium oryzae (sheath rot of rice) Alternaria sp. (grain discoloration of rice) and Fusarium sp. (scab of rye). Due to its innate antifungal potential wheat chitinase can be used to enhance fungal-resistance in crop plants.

The Triticum aestivum non-specific lipid transfer protein (TaLtp) gene family: comparative promoter activity of six TaLtp genes in transgenic rice

Plant non-specific lipid transfer proteins (nsLTPs) are encoded by a multigene family and support physiological functions, which remain unclear. We adapted an efficient ligation-mediated polymerase chain reaction (LM-PCR) procedure that enabled isolation of 22 novel Triticum aestivum nsLtp (TaLtp) genes encoding types 1 and 2 nsLTPs. A phylogenetic tree clustered the wheat nsLTPs into ten subfamilies comprising 1-7 members. We also studied the activity of four type 1 and two type 2 TaLtp gene promoters in transgenic rice using the 1-Glucuronidase reporter gene. The activities of the six promoters displayed both overlapping and distinct features in rice. In vegetative organs, these promoters were active in leaves and root vascular tissues while no beta-Glucuronidase (GUS) activity was detected in stems. In flowers, the GUS activity driven by the TaLtp7.2a, TaLtp9.1a, TaLtp9.2d, and TaLtp9.3e gene promoters was associated with vascular tissues in glumes and in the extremities of anther filaments whereas only the TaLtp9.4a gene promoter was active in anther epidermal cells. In developing grains, GUS activity and GUS immunolocalization data evidenced complex patterns of activity of the TaLtp7.1a, TaLtp9.2d, and TaLtp9.4a gene promoters in embryo scutellum and in the grain epicarp cell layer. In contrast, GUS activity driven by TaLtp7.2a, TaLtp9.1a, and TaLtp9.3e promoters was restricted to the vascular bundle of the embryo scutellum. This diversity of TaLtp gene promoter activity supports the hypothesis that the encoded TaLTPs possess distinct functions in planta.