Phosphinothricin (PPT) is a potent inhibitor of glutamine synthetase in plants and is used as a non‐selective herbicide. The bar gene which confers resistance in Streptomyces hygroscopicus to bialaphos, a tripeptide containing PPT, encodes a phosphinothricin acetyltransferase (PAT) (see accompanying paper). The bar gene was placed under control of the 35S promoter of the cauliflower mosaic virus and transferred to plant cells using Agrobacterium‐mediated transformation. PAT was used as a selectable marker in protoplast co‐cultivation. The chimeric bar gene was expressed in tobacco, potato and tomato plants. Transgenic plants showed complete resistance towards high doses of the commercial formulations of phosphinothricin and bialaphos. These data present a successful approach to obtain herbicide‐resistant plants by detoxification of the herbicide.
Histone deacetylation regulates gene expression during plant stress responses and is therefore an interesting target for epigenetic manipulation of stress sensitivity in plants. Unfortunately, overexpression of the core enzymes (histone deacetylases [HDACs]) has either been ineffective or has caused pleiotropic morphological abnormalities. In yeast and mammals, HDACs operate within multiprotein complexes. Searching for putative components of plant HDAC complexes, we identified a gene with partial homology to a functionally uncharacterized member of the yeast complex, which we called Histone Deacetylation Complex1 (HDC1). HDC1 is encoded by a single-copy gene in the genomes of model plants and crops and therefore presents an attractive target for biotechnology. Here, we present a functional characterization of HDC1 in Arabidopsis thaliana. We show that HDC1 is a ubiquitously expressed nuclear protein that interacts with at least two deacetylases (HDA6 and HDA19), promotes histone deacetylation, and attenuates derepression of genes under water stress. The fast-growing HDC1-overexpressing plants outperformed wild-type plants not only on well-watered soil but also when water supply was reduced. Our findings identify HDC1 as a rate-limiting component of the histone deacetylation machinery and as an attractive tool for increasing germination rate and biomass production of plants.
SummaryWe developed a novel, two-component transient gene silencing system in which the satellite tobacco mosaic virus (STMV) is used as vector for the delivery of inhibitory RNA into tobacco plants and the tobacco mosaic virus strain U2 (TMV-U2) is used as helper virus for supplying replication and movement proteins in trans. The main advantage of the system is that by uncoupling virus replication components from silencing induction components, the intensity of silencing becomes more pronounced. We call this system satellite virus-induced silencing system (SVISS) and will demonstrate here its robustness, speed and effectiveness. We were able to obtain pronounced and severe knockout phenotypes for a range of targeted endogenous genes belonging to various biochemical pathways and expressed in different plant tissues, such as genes involved in leaf and flower pigmentation, genes for cell wall synthesis in leaf, stem and root tissues or a ubiquitous RNA polymerase gene. By tandem insertion of more than one target gene sequence into the vector, we were able to induce simultaneous knockouts of an endogenous gene and a transgene. SVISS is the first transient gene silencing system for Nicotiana tabacum, which is a genetically well-characterized bridging species for the Solanaceae plant family.
The European corn borer, Ostrinia nubilalis (Hübner), is devastating insect pest in the corn (Zea mays L.) growing regions of North America and Europe. Field evaluations in the USA and Belgium showed that transgenic corn events expressing Cry9C, an insecticidal crystal protein from Bacillus thuringiensis subsp, tolworthi, very effectively control both generations of the European corn borer. Second to fourth instar larvae fed with leaf material of event CBH351 expressing the Cry9C protein all died within 4 d. Cry9C events, expressing high levels of the insecticidal protein, showed minimal stalk tunneling after heavy artificial infestations. Event CBH351 tested in plots containing only Cry9C transgenic plants had 0.14‐ and 0.09‐cm tunneling per stalk compared with more than 30‐ and 23‐cm tunneling per stalk for the negative controls, in the Belgium and Iowa field trial, respectively. In plots containing 30% non‐transgenic plants the event CBH351, showed only 1.45‐cm tunneling per stalk. Leaf, tassel, and pith tissue contained 39.0, 17.4, and 84.8 μg Cry9C protein mg−1 soluble protein, respectively, in analyses conducted at harvest of the Belgium trial. The implications of Cry9C use for resistance management strategies are discussed.
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