The Lupinus albus class-III chitinase gene, IF3, is constitutively expressed in vegetative organs and developing seeds

A cDNA fragment encoding a Lupinus albus. L. class-III chitinase, IF3, was isolated, using a cDNA probe from Cucumis sativus L., by in-situ plaque hyb ridization from a cDNA library constructed in the Uni-ZAP XR vector, with m RNAs isolated from mature lupin leaves. The cDNA had a coding sequence of 2 93 amino acids including a 27-residue N-terminal signal peptide. A class-II I chitinase gene was detected by Southern analysis in the L, albus genome. Western blotting experiments showed that the IF3 protein was constitutively present during seed development and in all the studied vegetative lupin or gans (i.e., roots, hypocotyls and leaves) at two growth stages (7- and 20-d -old plants). Accumulation of both the IF3 mRNA and IF3 protein was trigger ed by salicylic acid treatment as well as by abiotic (UV-C light and woundi ng) and biotic stress conditions (Colletotrichum gloeosporioides infection) . In necrotic leaves, IF3 chitinase mRNA was present at a higher level than that of another mRNA encoding a pathogenesis-related (PR) protein from L. albus (a PR-10) and that of the rRNAs. We suggest that one role of the IF3 chitinase could be in the defense of the plant against fungal infection, th ough our results do not exclude other functions for this protein.