, Volume 68, Issue 3, pp 191-199

Characterization and Functional Analysis of Class I and II Acidic Chitinase cDNA from Rough Lemon

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Two cDNAs encoding acidic chitinase (RlemAchiI and RlemAchiII) were identified from rough lemon (Citrus jambhiri Lush.). The deduced amino acid sequence of RlemAchiI has a typical N-terminal cysteine-rich domain, a proline/ glycine-rich hinge domain and a main structure, indicating that RlemAchiI encodes a class I chitinase. RlemAchiII encodes a class II acidic chitinase. RlemAchiI and RlemAchiII were expressed in Escherichia coli cells, and the fusion proteins had chitinase activity. Northern blot analysis revealed that the corresponding mRNA is inducible by wounding or microbe attack. The transcript was not constitutive but accumulated in leaves within 2 hr after wounding or inoculation with nonpathogenic isolates of Alternaria alternata. The RlemAchi was also induced, but appearance of the signal was delayed after inoculation with the rough lemon pathotype of A. alternata, which is pathogenic to rough lemon and produces a host-selective ACR-toxin.

Received 27 March 2002/ Accepted in revised form 23 May 2002