title: Brassica juncea chitinase BjCHI1 inhibits growth of fungal phytopathogens and agglutinates Gram-negative bacteria.
abstract: Brassica juncea BjCHI1 is a plant chitinase with two chitin-binding domains. Its expression, induced in response to wounding, methyl jasmonate treatment, Aspergillus niger infection, and caterpillar Pieris rapae feeding, suggests that it plays a role in defence. In this study, to investigate the potential of using BjCHI1 in agriculture, Pichia-expressed BjCHI1 and its deletion derivatives that lack one or both chitin-binding domains were tested against phytopathogenic fungi and bacteria. Transplastomic tobacco expressing BjCHI1 was also generated and its extracts assessed. In radial growth-inhibition assays, BjCHI1 and its derivative with one chitin-binding domain showed anti-fungal activities against phytopathogens, Colletotrichum truncatum, C. acutatum, Botrytis cinerea, and Ascochyta rabiei. BjCHI1 also inhibited spore germination of C. truncatum. Furthermore, BjCHI1, but not its derivatives lacking one or both domains, inhibited the growth of Gram-negative bacteria (Escherichia coli, Ralstonia solanacearum, Pseudomonas aeruginosa) more effectively than Gram-positive bacteria (Micrococcus luteus and Bacillus megaterium), indicating that the duplicated chitin-binding domain, uncommon in chitinases, is essential for bacterial agglutination. Galactose, glucose, and lactose relieved agglutination, suggesting that BjCHI1 interacts with the carbohydrate components of the Gram-negative bacterial cell wall. Retention of chitinase and bacterial agglutination activities in transplastomic tobacco extracts implicates that BjCHI1 is potentially useful against both fungal and bacterial phytopathogens in agriculture.
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Yuanfang
authors.initials: Y
authors.lastname: Guan
authors.forename: Sathishkumar
authors.initials: S
authors.lastname: Ramalingam
authors.forename: Dinesh
authors.initials: D
authors.lastname: Nagegowda
authors.forename: Paul W J
authors.initials: PW
authors.lastname: Taylor
authors.forename: Mee-Len
authors.initials: ML
authors.lastname: Chye
mesh_terms: D002688:Chitinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects* / Q000254:growth & development; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000254:growth & development; D009149:Mustard Plant / Q000201:enzymology* / Q000235:genetics; D010843:Pichia / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D013172:Spores, Fungal / Q000187:drug effects / Q000254:growth & development; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; D002688:Chitinases