The herbicide resistance to dicamba (HRd) biotype of kochia is resistant to several auxinic herbicides and is impaired in shoot gravitropism and other auxin-mediated responses. To better characterize the biotype and investigate its mechanism of resistance, we used messenger RNA (mRNA) differential display to compare patterns of dicamba-induced gene expression in HRd and susceptible (S1) plants. More than 60,000 complementary DNA fragments were generated and examined, 106 of which were isolated and used as probes on Northern blots to confirm gene expression levels. Steady-state levels of > 90% of mRNAs did not change after dicamba application. However, several mRNAs were detected whose levels were decreased, increased, or differentially regulated between the biotypes within minutes of dicamba treatment. The abundance of three mRNAs decreased after treatment, two of which had significant sequence similarity to choline monooxygenase and 5,10-methylenetetrahydrofolate reductase, respectively. Conversely, increased expression levels were observed for a putative chloride channel protein, 1-aminocyclopropane-1-carboxylate synthase, and an unknown gene. Genes differentially expressed between HRd and S1 plants included those similar to a putative translation initiation factor, xyloglucan endotransglycosylase, and a hypothetical protein cloned from several organisms. The results demonstrate that mRNA differential display is a useful technique for discovering genes that are rapidly regulated as part of a physiological response, and that this approach may provide insight into the mechanism of auxinic herbicide resistance in kochia.

The study of bovine mammary gland functional genomics requires appropriate cDNA library collections to access gene expression patterns from different developmental and physiological stages. The present study was undertaken with the objective to identify candidate genes involved in the process of increased milk synthesis following 0, 48 and 96 h of recombinant bovine somatotropin (rbST) treatment to Surti buffalo (Bubalus bubalis) through differential display reverse transcriptase PCR (DDRT-PCR). Of a total 50 sequenced DD bands, 64% of ESTs were differentially expressed (appeared only in post-treatment samples, i.e. 48 h and 96 h) and 36% were up-regulated after rbST treatment. Of the ESTs 32%were found to be located on Bos taurus chromosome 24 (equivalent to buffalo chromosome 22), whereas 16% of ESTs could not be mapped, indicating that they are specific to buffalo. Quantitative real time PCR assay of 15 ESTs revealed transcript level surge in 13 ESTs, and decline in one EST, while one showed up-regulation in expression level at 48 h while down-regulation at 96 h. This study indicates more than 30 novel transcripts, with unknown function, involved in increased milk synthesis and also the involvement of many more genes in the physiology of milk production than once thought.

Gene expression is known to vary significantly during the Leishmania life-cycle. Its monitoring might allow identification of molecular changes associated with the infective stages (metacyclics and amastigotes) and contribute to the understanding of the complex host-parasite relationships. So far, very few studies have been done on Leishmania (Viannia) braziliensis, one of the most pathogenic species. Such studies require, first of all, reference molecular markers. In the present work, we applied differential display analysis (DD analysis) in order to identify transcripts that might be (i) candidate markers of metacyclics and intracellular amastigotes of L. (V.) braziliensis or (ii) potential controls, i.e. constitutively expressed. In total, 48 DNA fragments gave reliable sequencing data, 29 of them being potential markers of infective stages and 12 potential controls. Eight sequences could be identified with reported genes. Validation of the results of DD analysis was done for 4 genes (2 differentially expressed and 2 controls) by quantitative real-time PCR. The infective insect stage-specific protein (meta 1) was more expressed in metacyclic-enriched preparations. The oligopeptidase b showed a higher expression in amastigotes. Two genes, glucose-6-phosphate dehydrogenase and a serine/threonine protein kinase, were found to be similarly expressed in the different biological samples.

Biomphalaria glabrata embryonic (Bge) cells have been shown to be a valuable in vitro cellular model for the study of snail host–parasite interactions. They both promote the growth and differentiation of various trematode species including Schistosoma mansoni, and Echinostoma caproni and share some morphological and functional features with circulating haemocytes. As an approach to investigate snail genes potentially regulated following exposure to trematode excretory–secretory (ES) products, we compared gene expression profiles of Bge cells exposed to saline solution, or saline solution containing ES products from S. mansoni or E. caproni, two trematode species parasitizing B. glabrata. Following differential display RT-PCR analysis we characterized 23 differentially displayed cDNAs and we focussed on the 5 cDNAs showing sequence similarity to known genes for expression validation. Using RT-PCR, we confirmed that ES products from S. mansoni and E. caproni differentially affect the expression levels of 4 out of the 5 transcripts. These partial transcripts corresponded to novel B. glabrata sequences, and showed significant sequence similarity to genes coding for (i) cytochrome C, (ii) methyl-binding proteins, (iii) glutamine synthetases, and (iv) protease inhibitors from the Kunitz family. The possible significance of these gene expression changes in host–parasite molecular interactions is discussed.

Changes in gene expression in Biomphalaria glabrata following infection with Schistosoma mansoni have been investigated using a modified differential display approach. RNA was extracted from ovotestis, mantle tissue and anterior nephridium of control and exposed snails at 2 time-points (4 h and 24 h) post-exposure and analysed by RNA fingerprinting. A number of transcripts were identified; some novel and some homologous to mRNAs in GenEMBL that were previously unknown in B. glabrata. Down regulation of one 241 bp mRNA expressed sequence fragment – with an open reading frame showing 48% identity to a cytochrome p450 over 80 residues – has been confirmed using semi-quantitative RT-PCR. Preliminary classification of B. glabrata cyp450 sequence shows it to fall into CLAN 2 of the cytochrome p450 superfamily. Differential display has been successful in identifying changes in gene expression in Biomphalaria glabrata upon infection with Schistosoma mansoni and promises to be a useful technique for the investigation of the interaction between host and parasite.

The potato cyst nematode (PCN) Globodera rostochiensis, like other parasitic nematodes, needs to synchronize its life-cycle with that of its host. This synchrony is achieved by the invasive-stage juvenile remaining dormant within its egg until stimulated to hatch by the presence of root diffusates of its host. Root diffusates may induce changes in gene expression in PCN, some of which may be important in the transition to a parasitic mode of existence. We have used a range of techniques including differential display to examine gene expression during stimulation and hatching of PCN. We find that few changes in gene expression appear to be induced directly by root diffusates. Instead, changes in gene expression seem to occur during or immediately after the hatching process. These results are discussed in the context of the host–parasite relationship.