No abstract

oxidizing enzyme (TrpOxE), which catalyzes the first step in Nitrilase (NIT) and myrosinase are important enzymes for tryptophan-dependent auxin biosynthesis in Brassicaceae, and auxin biosynthesis in Brassicaceae, which is increased during clubroot disease. Therefore, NIT and myrosinase levels during nitrilase were enhanced after treatment with jasmonic acid (JA) and methyl jasmonate. Similarly, the amount of myrosi-club development and possible regulation mechanisms were nase mRNA was increased by JA. During clubroot disease the investigated. In addition, the occurrence of different nitrilase isoforms in Chinese cabbage has been shown. Nitrilase activity endogenous concentration of JA increased in infected roots -5 weeks after inoculation. From our results it can be was enhanced in infected roots during later stages of club development (35-42 days after inoculation). However, no concluded that: (1) de novo indole-3-acetic acid (IAA) biosyndifferences in nitrilase mRNA levels between infected and thesis plays a role for symptom development of clubroot healthy roots were found during symptom development. My-disease in Brassicaceae during later developmental stages; and(2) JA which increased during club development, may be rosinase expression was increased in clubbed roots at slightly involved in the up-regulation of three enzymes important for earlier time points (28 days after inoculation) and also at later time points during infection. The activities of tryptophan IAA synthesis.

The host range of the soilborne obligate biotroph, Plasmodiophora brassicae was investigated. Evidence is presented that infection by P. brassicae might occur in non-Brassica species, leading to the potential formation of resting spores. Structures resembling P. brassicae were found in the root cortex of Tropaeolum majus, Carica papaya, Reseda alba and Beta vulgaris as demonstrated by scanning electron microscopy. Inoculation of Brassica rapa roots with spores extracted from either T. majus or B. vulgaris roots which had been previously inoculated with P. brassicae led to development of clubroot in the roots of B. rapa. It was also shown that the development of the symptom might be correlated with glucosinolate content, although other host factors are implicated in the B. vulgaris interaction with P. brassicae. In the glucosinolate-containing non-Brassicas, T. majus and C. papaya, the concentrations of benzylglucosinolate increased markedly in roots inoculated with P. brassicae, compared with the controls. There were also increases in concentrations of benzylglucosinolate in leaves of T. majus after P. brassicae infection. However, in R. alba roots, the total glucosinolate content decreased after inoculation with P. brassicae compared with the controls. High root concentrations of 2-OH-2-phenylethylglucosinolate (glucobarbarin) compared with low root indole glucosinolates in this species might limit P. brassicae infection and development. The importance of our investigations in relation to cultivation of non-Brassica species on fields infested with P. brassicae is discussed.

The in vitro conversion of [14C]‐tryptophan to [14C]‐indole‐3‐acetaldoxime (IAOX) by microsomal membranes of Chinese cabbage (Brassica campestris ssp. pekinensis cv. Granat) has been studied. The reaction product was identified by thin‐layer chromatography (TLC) and high performance liquid chromatography (HPLC). Furthermore. IAOX was identified as an endogenous compound of Chinese cabbage by mass spectroscopy. The tryptophan‐oxidizing enzyme (TrpOxE) was characterized. MnCl2 was required as cofactor, H2O2, and 2,4‐dichlorophenol (DCP) stimulated the reaction. The enzyme showed a pH optimum at pH 8–9 and a Km for l‐tryptophan of 20 μM. The membranes containing TrpOxE activity were identified as plasma membranes by means of aqueous polymer two‐phase partitioning. The TrpOxE from Chinese cabbage was purified 3‐fold from plasma membranes by solubilization followed by (NH4)2SO4‐fractionation, affinity‐chromatography with concanavalin A, and native gel electrophoresis. Enzyme activity was reduced by a tunicamycin pretreatment. Several other plant species, e.g. maize (Zea mays L. Inrakorn), sunflower (Helianthus annuus L. cv. Hohes Sonnengold), tobacco (Nicotiana tabacum L. cv. White Burley), and pea (Pisum sativum L. cv. Krombeck) showed a similar conversion of [14C]‐tryptophan to [14C]‐IAOX by phase‐partitioned plasma membranes.

Cytokinin‐like substances in both healthy and infected (Plasmodiophora brassicae) Wor. strain S) roots of Brassica campestris L. ssp. pekinensis cv. Granat have been tentatively identified and quantified by HPLC. The isomers of the cytokinins could be seperated on a reversed phase column using a gradient elution with increasing amounts of methanol. Secondary plasmodia were isolated mechanically from Plasmodiophora brassicae infected roots. The time course of adenine uptake and its conversion to cytokinins were investigated. Evidence is presented for the incorporation of [U‐14C]‐adenine into trans‐zeatin by secondary plasmodia.