Pectin methylesterases (PMEs) play an essential role during plant development by a¡ecting the mechanical properties of the plant cell wall. Previous work indicated that plant PMEs may be subject to post-translational regulation. Here, we report the analysis of two proteinaceous inhibitors of PME in Arabidopsis thaliana (AtPMEI1 and 2). The functional analysis of recombinant AtPMEI1 and 2 proteins revealed that both proteins are able to inhibit PME activity from £owers and siliques. Quantitative RT-PCR analysis indicated that expression of AtPMEI1 and 2 mRNAs is tightly regulated during plant development with highest mRNA levels in £owers. Promotor: :GUS fusions demonstrated that expression is mostly restricted to pollen.

The expression of nitrilase in Arabidopsis during the development of the clubroot disease caused by the obligate biotroph Plasmodiophora brassicae was investigated. A time course study showed that only during the exponential growth phase of the clubs was nitrilase prominently enhanced in infected roots compared with controls. NIT1 and NIT2 are the nitrilase isoforms predominantly expressed in clubroot tissue, as shown by investigating promoter-␤-glucuronidase fusions of each. Two peaks of ␤-glucuronidase activity were visible: an earlier peak (21 d post inoculation) consisting only of the expression of NIT1, and a second peak at about 32 d post inoculation, which predominantly consisted of NIT2 expression. Using a polyclonal antibody against nitrilase, it was shown that the protein was mainly found in infected cells containing sporulating plasmodia, whereas in cells of healthy roots and in uninfected cells of inoculated roots only a few immunosignals were detected. To determine which effect a missing nitrilase isoform might have on symptom development, the P. brassicae infection in a nitrilase mutant (nit1-3) of Arabidopsis was investigated. As a comparison, transgenic plants overexpressing NIT2 under the control of the cauliflower mosaic virus 35S promoter were studied. Root galls were smaller in nit1-3 plants compared with the wild type. The phenotype of smaller clubs in the mutant was correlated with a lower free indole-3-acetic acid content in the clubs compared with the wild type. Overexpression of nitrilase did not result in larger clubs compared with the wild type. The putative role of nitrilase and auxins during symptom development is discussed.

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The mature embryos of fourteen elite winter wheat cultivars have been transformed by a biolistic approach. The gene coding for γ-glutamylcysteine synthetase (EC 6.3.2.2) was used as a transgene in order to obtain stable transformants resistant to drought stress. A binary vector, pBinarUTRECS, was used. The gene was under the control of the CaMV35S promoter region. GUS::GFP gene fusion was used as a reporter system and nptII served as a selectable marker gene. A high regeneration capacity of callus tissue under the selective pressure and successful GUS assay of transformed tissue were an indication of successful insertion of a transgene into mature embryo derived wheat tissue.