Identification, Characterization, and Regulation of a Novel Antifungal Chitosanase Gene ( cho ) in Anabaena spp

Abstract

Two contrasting cyanobacterial species (Anabaena fertilissima and Anabaena sphaerica) were selected based on differences in antifungal behavior in order to study the mechanism for production of an antifungal enzyme and the genes responsible for this production. In A. fertilissima, chitosanase and antifungal activities were increased significantly under of growth-limiting conditions (8 of light and 16 h of darkness). The lack of such activities in A. sphaerica was associated with high levels of protein that accumulated during the stationary phase (at 28 days) under the same light conditions. The gene putatively responsible for chitosanase and antifungal activities was amplified using specific primers, and sequence analysis of the amplified products (1.086 and 1.101 kb in A. sphaerica and A. fertilissima, respectively) showed that they belong to the glycoside hydrolase 3 ( Cyanobacteria comprise a heterogeneous assemblage of photosynthetic prokaryotes having extraordinary biosynthetic potential and a repertoire of diverse metabolic activities. They are an important source of novel antifungal, antibacterial, and herbicidal or weedicidal compounds, which have been implicated in allelopathic interactions in water and soil (29). A majority of these metabolites are biologically active and are products of either nonribosomal polypeptide (NRP) or mixed polyketide-NRP biosynthetic pathways. The toxins produced by cyanobacteria are greatly influenced by various physiological and environmental factors, including light, temperature, nutrients, and pH (5).The antifungal properties of cyanobacterial metabolites, most of which have not been exploited, have immense potential in agriculture for use against fungal plant pathogens. In bacteria, lytic enzymes, such as chitinases, chitosanases, proteases, and ␤-1,3-glucanases, are known to have key roles in biocontrol of various soilborne fungal pathogens. Chitin is a linear polymer of 1,4-linked N-acetyl-D-glucosamine (GlcNAc) residues, and the deacetylated derivative of chitin is chitosan. In contrast to chitin, chitosan has been found in very few organisms, but it has been found in members of the Zygomycota, such as Mucor rouxii (42), Absidia coerulea (22), and Rhizopus oryzae (8). The filamentous fungi Lentinus edodes andPleurotus sajo-caju were investigated to determine their abilities to produce chitosan (30). Chitosan and chitosan-glucan complexes have been found in the mycelia of Aspergillus niger, Humicola lutea, and Fusarium moniliforme (39). Chitosanases (EC 3.2.1.132) produced by bacteria are classified into five glycoside hydrolase (GH) families (families 5, 8, 46, 75, and 80) (6, 10, 11, 12, 13). Families 5 and 8 are composed of enzymes that are hydrolytic with glycosides, and the family 46, 75, and 80 enzymes studied so far are chitosanases. This classification of chitosanases is based on amino acid sequence similarities of the catalytic domains. Recently, the family 46 chitosanase of Amycolatopsis sp. CsO-2 responsible for antifungal activity against Rhizopus oryzae ...

Deciphering the biochemical spectrum of novel cyanobacterium-based biofilms for use as inoculants

“…In recent years, the production of bioactive compounds/enzymes by cyanobacteria and their role in biocontrol and plant growth promotion have been extensively investigated in laboratory and field conditions (Kulik 1995;Jaiswal et al 2008;Dukare et al 2011 for the first time revealed the activity of hydrolytic enzymes in several Anabaena strains and their correlation with antifungal activity. Chitosanase homologues and microcystin-like compounds were identified in two promising strains, Anabaena laxa and Anabaena Iyengarii, which exhibit fungicidal activity (Prasanna et al 2010a;Gupta et al 2010Gupta et al , 2011Gupta et al , 2012, and a novel antifungal chitosanase (cho) gene belonging to glycoside hydrolase family-3 from Anabaena fertilissima was characterized (Gupta et al 2010). Antifungal b-1,4-endoglucanases end and end 1 encoded by Calothrix elenkinii (Natarajan et al 2012) and Anabaena sp.…”

Prospecting Cyanobacteria-Fortified Composts as Plant Growth Promoting and Biocontrol Agents in Cotton

“…The significance of cyanobacteria as producers of cyanotoxins and other novel bioactive molecules is globally recognised (Jaiswal et al ., 2008; Mundt et al ., 2001); however, their chemical potential is less explored in agriculture, especially as biocontrol agents. Few reports are available on the activity of hydrolytic enzymes such as chitosanases, xylanases and endoglucanases in Anabaena strains (Gupta et al ., 2010; Prasanna et al ., 2008) and their positive correlation with fungicidal activity. This has diversified the significant role of cyanobacteria beyond nitrogen fixation or phytohormones-mediated plant growth promotion (Nayak et al ., 2004; Prasanna et al ., 2009, 2012; Sergeeva et al ., 2002).…”

Influence of phosphorus and pH on the fungicidal potential of Anabaena strains

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