Plant Science 160 (2001) 405–414 Enhanced resistance to sheath blight by constitutive expression of infection-related rice chitinase in transgenic elite indica rice cultivars Karabi Datta a , Jumin Tu a , Norman Oliva a , Isabelita Ona b , Rethinasamy Velazhahan a,c,d , Twng Wah Mew b , Subbaratnam Muthukrishnan d , Swapan K. Datta a, * a Plant Breeding, Genetics, and Biochemistry Diision, International Rice Research Institute, MCPO Box 3127, 1271 Makati City, Philippines b Entomology and Plant Pathology Diision, International Rice Research Institute, MCPO Box 3127, 1271 Makati City, Philippines c Department of Plant Pathology, Tamil Nadu Agricultural Uniersity, Coimbatore, India d Department of Biochemistry, Kansas State Uniersity, Manhattan, KS 66506 -3702, USA Received 13 June 2000; received in revised form 5 September 2000; accepted 6 September 2000 Abstract Genetic transformation has been attempted for management of rice sheath blight disease, caused by Rhizoctonia solani. We introduced a PR-3 rice chitinase gene (RC7 ), isolated from R. solani -infected rice plants, into indica rice cultivars IR72, IR64, IR68899B, MH63, and Chinsurah Boro II by the biolistic and PEG-mediated transformation system. Inheritance was studied up to the T 2 generation by Southern blot analysis. Western blot analysis of transgenic plants with polyclonal antibody revealed the presence of chitinase protein with a molecular weight of 35 kDa that reacts with chitinase antibody. The transformants synthesized different levels of chitinase proteins constitutively and progeny from the plants containing the chitinase gene showed different levels of enhanced resistance when challenged with the sheath blight pathogen R. solani. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Sheath blight; Chitinase; Transgenic rice; Enhanced resistance www.elsevier.com/locate/plantsci 1. Introduction Consistently confronted by biotic and abiotic stresses, plants have evolved a battery of self-de- fense systems to protect themselves from pathogen attack. Once this battery of self-defense system is activated, plants synthesize an array of proteins whose apparent function is to restrict the growth of invading organisms [1–3]. One class of these pathogenesis-related proteins is chitinase. Chitinase catalyzes the hydrolysis of -1,4-link- age of the N -acetylglucosamine polymer of chitin, which is a major component of the fungal cell wall but is not found in higher plants [4]. With this hydrolysis ability, chitinase is therefore capable of inhibiting growth of the pathogen by lysing its hyphal tips, particularly in combination with glu- canase [5–9]. In addition to this direct action, the released oligomers of N -acetylglucosamine could function as elicitors to further amplify this defense response in cells surrounding a site of infection [10]. Moreover, some chitinase also displays lysozymal activity and thus may be involved in conferring resistance to bacterial pathogens [4,11]. The antifungal activity of plant chitinase makes this protein an attractive candidate for engineering enhanced natural resistance by constitutive expres- sion of normally inducible defense genes. The first report of success with this approach was the ex- * Corresponding author. Tel.: +63-2-8450563/8127686; fax: +63- 2-8911292/7612406. E-mail address: sdatta@cgiar.org (S.K. Datta). 0168-9452/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0168-9452(00)00413-1