ARABIDOPSIS-THALIANA CLASS-IV CHITINASE IS EARLY INDUCED DURING THE INTERACTION WITH XANTHOMONAS-CAMPESTRIS

Endochitinases are widely distributed among higher plants, including a number of important crop species, They are generally considered to be involved in plant defence against potential pathogens. We have cloned a class IV chitinase gene (AtchitIV) from Arabidopsis thaliana. South ern blot analysis allowed the detection of two cross-hybridising genes in the A. thaliana genome, AtchitIV transcripts are detected in seedp ods, but not in roots, inflorescence stems, leaves and flowers of heal thy plants, The transcripts accumulated very rapidly in leaves after i noculation with Xanthomonas campestris. Maximum mRNA accumulation was reached one hour after infection and decreased to very low levels 72 h ours after induction. This result suggests an involvement of AtchitIV in the initial events of the hypersensitive reaction, Nevertheless, A. thaliana plants transformed with the gus gene under the control of a class IV chitinase bean promoter, showed GUS activity in seed embryos, These data, together with the constitutive expression of the endogeno us gene in the seedpods, points to additional physiological roles for this protein. (C) 1997 Federation of European Biochemical Societies.