Isolation and Characterization of an Elicitor of Necrosis Isolated from Intercellular Fluids of Compatible Interactions of Cladosporium fulvum (Syn. Fulvia fulva) and Tomato

Abstract

Intercellular fluids of compatible race-cultivar interactions of Cladosporium fulvum and tomato contain specific elicitors of necrosis. These elicitors which are of fungal origin induce chlorosis and necrosis in resistant but not in susceptible plants. With the tomato cultivar Sonatine (carrying resistance gene Cf9, resistant to the fungal races 0, 4, 5, 2, 2.4, and 2.4.5 but susceptible to race 2.4.5.9) as the test plant for assaying necrosis-inducing activity, we isolated and partially characterized an elicitor of necrosis on this cultivar. The elicitor bound to CM-Sephadex but not to DEAE-Sephadex; it was stable to heat (10 minutes at 100°C), HCI (0.01 normal), NaOH (0.01 normal), and NaIO4 (0.02 molar), sensitive to pronase and protease (from Bacillus polymyxa) but not to other proteases such as a-chymotrypsin and trypsin. After electrophoresis of partially purified elicitor preparations under low pH conditions, the necrosis-inducing activity was association with a peptide with an apparent molecular weight of 5500. Races 0, 4, 5, 2.4, and 2.4.5 but not race 2.4.5.9 produced this elicitor in high yields. The elicitor is probably a product of avirulence gene A9 which is present in all races except in race 2.4.5.9 and induces necrosis in cultivars carrying resistance gene Cf9.

Monoclonal Antibodies to Glycoprotein Antigens of a Fungal Plant Pathogen, Phytophthora megasperma f. sp. glycinea

“…3B). These mAbs showed dramatically lower levels of binding to glycoproteins of race 4 and race A when compared to race 1, but they reacted to mycelial walls of the three races equivalently.…”

Ethylene Biosynthesis-Inducing Xylanase

“…The xylanase activity kinetics of the EIXs isolated from (9,25), perhaps a specific receptor for the EIX protein existing on Xanthi tobacco cells is responsible for the induction of ethylene biosynthesis. This does not completely discount the possibility that xylan fragments produced by EIX may be responsible for some ofthe other pathologic symptoms seen in EIX-treated tissues, particularly given the observation that heat-stable cell wall fragments released by another fungal xylanase can kill plant cells (6).…”

“…However, polypeptide products of pathogenic fungi harboring no apparent enzymatic activities also stimulate ethylene biosynthesis (25) and cause tissue necrosis in plants (9). This paper examines the endoxylanase and ethylene biosynthesis-inducing activities of two EIX proteins in parallel in an effort to identify enzymatic products that might be responsible for inducing defense responses in tobacco tissue.…”

Cladosporium fulvum Effectors: Weapons in the Arms Race with Tomato

“…His coworkers had isolated race-specific suppressors from Phytophthora infestans (34), and as we initially expected to find suppressors of defense responses in AFs of infected leaves, a stay in his laboratory was a good choice. It took several years to purify the Avr9 protein (24) and even longer to determine its amino acid (aa) sequence, which required an extremely pure protein to be analyzed by Edman degradation. Eventually, we purified the Avr9 protein using reversed phase chromatography (79) and were able to determine its aa sequence.…”