SummarySnowdrop lectin (Galanthus nivalis agglutinin; GNA) has been shown previously to be toxic towards rice brown planthopper (Nilaparvata lugens; BPH) when administered in artificial diet. BPH feeds by phloem abstraction, and causes 'hopper burn', as well as being an important virus vector. To evaluate the potential of the gna gene to confer resistance towards BPH, transgenic rice (Oryza sativa L.) plants were produced, containing the gna gene in constructs where its expression was driven by a phloemspecific promoter (from the rice sucrose synthase RSs1 gene) and by a constitutive promoter (from the maize ubiquitin ubi1 gene). PCR and Southern analyses on DNA from these plants confirmed their transgenic status, and that the transgenes were transmitted to progeny after selffertilization. Western blot analyses revealed expression of GNA at levels of up to 2.0% of total protein in some of the transgenic plants. GNA expression driven by the RSs1 promoter was tissue-specific, as shown by immunohistochemical localization of the protein in the non-lignified vascular tissue of transgenic plants. Insect bioassays and feeding studies showed that GNA expressed in the transgenic rice plants decreased survival and overall fecundity (production of offspring) of the insects, retarded insect development, and had a deterrent effect on BPH feeding. gna is the first transgene to exhibit insecticidal activity towards sap-sucking insects in an important cereal crop plant.

The heat shock response of Escherichia coli is under the positive control of the r32 protein (the product of the rpoH gene). We found that overproduction of the if32 protein led to concomitant overproduction of the heat shock proteins, suggesting that the intracellular i32 levels limit heat shock gene expression. In support of this idea, the intracellular half-life of the if32 protein synthesized from a multicopy plasmid was found to be extremely short, e.g., less than 1 min at 37 and 42°C. The half-life increased progressively with a decrease in temperature, reaching 15 min at 22°C. Finally, conditions known previously to increase the rate of synthesis of the heat shock proteins, i.e., a mutation in the dnaK gene or expression of phage A early proteins, were shown to simultaneously result in a three-to fivefold increase in the half-life of if32.All organisms so far tested respond to a sudden upshift in growth temperature by increasing the synthesis of a set of proteins, a phenomenon called the heat shock response. In Escherichia coli, there is a set of about 20 proteins (called the heat shock proteins) whose synthesis is thereby increased (see reference 27 for a review). The amino acid sequences of at least some heat shock proteins in distantly related organisms, including Drosophila melanogaster and Homo sapiens, are remarkably similar to those in E. coli (4,5,21), suggesting that the heat shock response is of ancient origin and fundamental importance to cellular physiology. The function of the heat shock proteins, however, is unclear, although it has been shown that they play roles in the assembly and disassembly of macromolecular complexes (GroE [15, 16, 21, In E. coli, heat shock protein synthesis rates peak at about 5 min after a temperature upshift (e.g., from 30 to 42°C) and then decline rapidly to new steady-state levels that are characteristic of the new ambient temperature. Initiation of the heat shock response is regulated transcriptionally. It has been shown that the RNA polymerase core (E) binds to a new initiation subunit, c32 (30), and the resulting holoenzyme, E-&32, transcribes only heat shock genes (19), which have promoter sequences that differ from those transcribed by E plus U70, the normal vegetative initiation factor (8). The transcription factor U70 iS itself a heat shock protein, so the increase in its concentration after heat shock may contribute to the decline in heat shock protein synthesis. Furthermore, other heat shock proteins, in particular the dnaK gene product, contribute to the shutoff, since mutations in their genes prolong the high-level synthesis of heat shock proteins (34). The heat shock response must be tightly regulated in order to allow rapid changes in heat shock protein synthesis rates. Although the level of mRNA from the rpoH gene (which encodes U32) increases after heat shock (11,12,36 Technology, Cambridge, MA 02139. this increase is insufficient and too slow to be the sole explanation of the rapid effect of heat shock. In this paper, we show that the concen...

Wild Brassica plants release seeds by a pod shattering mechanism; in related crop plants, such as oil‐seed rape, this can result in substantial loss of seed, and hence loss of revenue, and also in the distribution of seeds which can contaminate future crops and the environment. To identify strategies which may be used to reduce shatter, either by conventional breeding programmes or by genetic engineering, we have examined fruit development in oil‐seed rape (Brassica napus), and in the related B. juncea and Arabidopsis, using a combination of cytological, cytochemical and molecular techniques. We report here on the patterns of cellular differentiation and tissue development during fruit maturation, and suggest how this results in the shattering phenotype.

Because of the highly conserved pattern of expression of the eucaryotic heat shock genes hsp7O and hsp84 or their cognates during sporulation in Saccharomyces cerevisiae and development in higher organisms, the role of the Escherichia coli homologs dnaK and htpG was examined during the response to starvation. The htpG deletion mutant was found to be similar to its wild-type parent in its ability to survive starvation for essential nutrients and to induce proteins specific to starvation conditions. The dnaK103 mutant, however, was highly susceptible to killing by starvation for carbon and, to a lesser extent, for nitrogen and phosphate. Analysis of proteins induced under starvation conditions on two-dimensional gels showed that the dnaK103 mutant was defective for the synthesis of some proteins induced in wild-type cells by carbon starvation and of some proteins induced under all starvation conditions, including the stationary phase in wild-type cells. In addition, unique proteins were synthesized in the dnaK103 mutant in response to starvation. Although the synthesis of some proteins under glucose starvation control was drastically affected by the dnaK103 mutation, the synthesis of proteins specifically induced by nitrogen starvation was essentially unaffected. Similarly, the dnaKl03 mutant was able to grow, utilizing glutamine or arginine as a source of nitrogen, at a rate approximate to that of the wild-type parent, but it inefficiently utilized glycerol or maltose as carbon sources. Several differences between the protein synthetic pattern of the dnaK103 mutant and the wild type were observed after phosphate starvation, but these did not result in a decreased ability to survive phosphate starvation, compared with nitrogen starvation.In all organisms, a sudden increase in temperature or an exposure to ethanol or heavy metals results in the transient induction of a small set of proteins concomitant with the transient shutdown of the synthesis of many constitutive proteins (7,20,25,26). Three of the proteins which are induced by heat shock are highly conserved among both procaryotes and eucaryotes. DnaK and HtpG (C62.5) of Escherichia coli are approximately 48 and 41% homologous to Hsp7O and Hsp84 of Drosophila melanogaster, respectively (1, 2). The third is GroEL, which has recently been found to be homologous to a Tetrahymena thermophila mitochondrial protein, Hsp58 (22), to the Saccharomyces heat shock protein Hsp6O (31), and to the Rubisco subunitbinding protein of plants (16). In addition to being induced by heat shock and other stresses, the heat shock proteins, or closely related proteins called cognates, are induced in the absence of heat shock during aging and during early development of several eucaryotes (11,18,44). Because of the high conservation of the pattern of induction of Hsp84, Hsp26, and cognates of Hsp7O during sporulation in yeast and embryogenesis in D. melanogaster, it has been proposed that the induction of these proteins constitutes an ancient developmental pathway (18). The rudiments o...

Abstract. The expression of extA, an extensin gene fromBrassica napus L. (oilseed rape) was examined in transgenic Nicotiana tabacum L. (tobacco) and untransformed Brassicajuncea L. and B. napus tissues. Northern analysis showed that this gene maintained its normal pattern of expression when transferred to tobacco. In transgenic tobacco plants containing an extA promoter/13-glucuronidase coding sequence fusion, expression of extA was detected in the external and internal phloem of the main stem. High expression levels were seen in cortical parenchyma cells at the point where the axillary flowering branch joined the main stem. Expression was greatest in regions where the maximum tensile stress would seem to be exerted on the main stem by the weight of the axillary branch. It was confirmed that this expression pattern was due to tensile stress by using weights to induce expression of the fusion gene in axillary flowering stalks. In B. juncea pods, in-situ hybridisation studies showed that the extensin gene was strongly expressed in cells of the carpel walls within which considerable tensile stresses develop.