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Large seeded grain legumes such as the common bean (Phaseolus vulgaris) and cowpea (Vigna unguiculata) are very important crops with seeds that are major protein source for people in developing countries, but their yields and improvement lag behind the economically more important cereals. For research purposes, genetic transformation is a powerful tool to obtain valuable information on gene expression and putative gene functions. In addition, through genetic transformation, candidate genes can be evaluated for their potential in agricultural biotechnology applications, such as resistance against biotic stresses. However, it remains difficult to stable genetically transform large seeded grain legumes such as Phaseolus and cowpea using Agrobacterium tumefaciens. In this paper a system is described to obtain so-called transgenic composite plants from P. vulgaris. These have a transgenic root system, obtained through Agrobacterium rhizogenes transformation of de-rooted seedlings. Their potentials for studies on important processes in the root system will be discussed.

International audience; The Nicotiana plumbaginifolia gn1 gene encoding a beta-1,3-glucanase isoform has been characterized. The gn1 product represents an isoform distinct from the previously identified tobacco beta-1,3-glucanases. By expressing gn1 in Escherichia coli, we have determined directly that the encoded protein does, indeed, correspond to a beta-1,3-glucanase. In N. plumbaginifolia, gn1 was found to be expressed in roots and older leaves. Transgenic tobacco plants containing the 5'-noncoding region of gn1 fused to the beta-glucuronidase (GUS) reporter gene also showed maximum levels of GUS activity in roots and older leaves. No detectable activity was present in the upper part of the transgenic plants with the exception of stem cells at the bases of emerging shoots. The expression conferred by the gn1 promoter was differentially induced in response to specific plant stress treatments. Studies of three plant-bacteria interactions showed high levels of GUS activity when infection resulted in a hypersensitive reaction. Increased gene expression was confined to cells surrounding the necrotic lesions. The observed expression pattern suggests that the characterized beta-1,3-glucanase plays a role both in plant development and in the defense response against pathogen infection.

Promoter trapping has been performed through integration of a T-DNA containing a promoterless beta-glucuronidase (gus) reporter gene into the genome of Arabidopsis thaliana. A collection of T-DNA-tagged Arabidopsis lines has been produced with the vector pdeltagusBin19. Part of this collection was screened for lines with specific gus expression patterns. Here we report on the identification of two lines with gus expression in anthers and seeds. Both lines harbour complex T-DNA inserts. In one line, the integration of the T-DNA causes a male sterility phenotype and gus expression is developmentally regulated in anthers and flower bases. In the other line expression of gus is seen in the anther and seed endosperm.

Three glycine-rich protein genes of Arabidopsis thaliana (Atgrp-6, Atgrp-7, and Atgrp-8) that correspond to putative genes coding for pollenins (AtolnB;2, AtolnB;3, and AtolnB;4, respectively) are expressed predominantly in the anthers and, more specifically, in the tapetum layer. Tapetal cells are responsible for nutrition of developing pollen grains and show some functional similarities to nematode feeding sites (NFS) induced in plant roots by sedentary parasitic nematodes. The aim of this study was to analyze promoter activity of the Atgrp genes in NFS. Transformed Arabidopsis plants containing a promoter-ss-glucuronidase (gus) fusion of the Atgrp-7 gene were inoculated with the root-knot nematode Meloidogyne incognita and the cyst nematode Heterodera schachtii. GUS assays were performed at different time points after infection. Histochemical analysis revealed an up-regulation of Atgrp-7-gus expression 3 days after inoculation in the feeding sites of both nematodes. Maximal Atgrp-7-gus staining levels in NFS were observed 1 week after nematode infection.

Sedentary nematodes are important pests of crop plants. They are biotrophic parasites that can induce the (re)differentiation of either differentiated or undifferentiated plant cells into specialized feeding cells. This (re)differentiation includes the reactivation of the cell cycle in specific plant cells finally resulting in a transfer cell-like feeding site. For growth and development the nematodes fully depend on these cells. The mechanisms underlying the ability of these nematodes to manipulate a plant for its own benefit are unknown. Nematode secretions are thought to play a key role both in plant penetration and feeding cell induction. Research on plant-nematode interactions is hampered by the minute size of cyst and root knot nematodes, their obligatory biotrophic nature and their relatively long life cycle. Recently, insights into cell cycle control in Arabidopsis thaliana in combination with reporter gene technologies showed the differential activation of cell cycle gene promoters upon infection with cyst or root knot nematodes. In this review, we integrate the current views of plant cell fate manipulation by these sedentary nematodes and made an inventory of possible links between cell cycle activation and local, nematode-induced changes in auxin levels

Les systèmes d'inoculation in vitro sont des outils performants et précis pour l'étude des interactions plantes-nématodes. L'obtention de juvéniles stériles est une étape cruciale pour la plupart de ces systèmes. La majorité des protocoles publiés comprennent une désinfection des juvéniles, ce qui conduit à une mortalité élevée. Nous décrivons ici une nouvelle méthode pour désinfecter, rapidement, facilement, et à faible coût des nématodes du genre #Globodera$, en partant de kystes. La mortalité des juvéniles désinfectés est faible (entre 10 et 40% au maximum). Les juvéniles stérilisés infestent les racines de pomme de terre cultivées in vitro et s'y développent normalement. (Résumé d'auteur)