IMMUNOHISTOLOGICAL LOCALIZATION OF A BASIC CLASS-IV CHITINASE IN BETA-VULGARIS LEAVES AFTER INFECTION WITH CERCOSPORA-BETICOLA

The subcellular distribution of a basic class IV chitinase (Ch4) in Ce rcospora beticola-infected sugar beets has been studied by immunohisto logical analysis. Ch4 was primarily deposited in extracellular globuli proximal to the necrosis. High levels of Ch4 were observed in the vic inity of the necrotic lesions, low levels were found at distant sites from the necrosis. This plant-pathogen interaction thus gives rise to a local induction of Ch4, whereas no apparent systemic induction of Ch 4 was found. After infection with Cercospora, a tolerant sugar beet cu ltivar accumulated Ch4 faster than a susceptible one, and the protein was spatially distributed over a comparatively larger area in the tole rant variety. In the tolerant beet cultivar symptoms appear a few days later. and the number of necroses are reduced and smaler than in the sensitive cultivar. In uninfected sugar beet leaves, Ch4 is present in low amounts in epidermis, stomata and xylem cells. A specific autoflu orescence and a high endogenous beta-glucuronidase activity in Cercosp ora were used to demonstrate that this pathogen did not penetrate the tissue beyond the necrosis.