Transcriptional responses of Arabidopsis thaliana plants to As (V) stress

Background Arsenic is toxic to plants and a common environmental pollutant. There is a strong chemical similarity between arsenate [As (V)] and phosphate (Pi). Whole genome oligonucleotide microarrays were employed to investigate the transcriptional responses of Arabidopsis thaliana plants to As (V) stress. Results Antioxidant-related genes (i.e. coding for superoxide dismutases and peroxidases) play prominent roles in response to arsenate. The microarray experiment revealed induction of chloroplast Cu/Zn superoxide dismutase (SOD) (at2g28190), Cu/Zn SOD (at1g08830), as well as an SOD copper chaperone (at1g12520). On the other hand, Fe SODs were strongly repressed in response to As (V) stress. Non-parametric rank product statistics were used to detect differentially expressed genes. Arsenate stress resulted in the repression of numerous genes known to be induced by phosphate starvation. These observations were confirmed with qRT-PCR and SOD activity assays. Conclusion Microarray data suggest that As (V) induces genes involved in response to oxidative stress and represses transcription of genes induced by phosphate starvation. This study implicates As (V) as a phosphate mimic in the cell by repressing genes normally induced when available phosphate is scarce. Most importantly, these data reveal that arsenate stress affects the expression of several genes with little or unknown biological functions, thereby providing new putative gene targets for future research

Genetic load and transgenic mitigating genes in transgenic \u3ci\u3eBrassica rapa\u3c/i\u3e (field mustard) × \u3ci\u3eBrassica napus\u3c/i\u3e (oilseed rape) hybrid populations

Abstract Background One theoretical explanation for the relatively poor performance of Brassica rapa (weed) × Brassica napus (crop) transgenic hybrids suggests that hybridization imparts a negative genetic load. Consequently, in hybrids genetic load could overshadow any benefits of fitness enhancing transgenes and become the limiting factor in transgenic hybrid persistence. Two types of genetic load were analyzed in this study: random/linkage-derived genetic load, and directly incorporated genetic load using a transgenic mitigation (TM) strategy. In order to measure the effects of random genetic load, hybrid productivity (seed yield and biomass) was correlated with crop- and weed-specific AFLP genomic markers. This portion of the study was designed to answer whether or not weed × transgenic crop hybrids possessing more crop genes were less competitive than hybrids containing fewer crop genes. The effects of directly incorporated genetic load (TM) were analyzed through transgene persistence data. TM strategies are proposed to decrease transgene persistence if gene flow and subsequent transgene introgression to a wild host were to occur. Results In the absence of interspecific competition, transgenic weed × crop hybrids benefited from having more crop-specific alleles. There was a positive correlation between performance and number of B. napus crop-specific AFLP markers [seed yield vs. marker number (r = 0.54, P = 0.0003) and vegetative dry biomass vs. marker number (r = 0.44, P = 0.005)]. However under interspecific competition with wheat or more weed-like conditions (i.e. representing a situation where hybrid plants emerge as volunteer weeds in subsequent cropping systems), there was a positive correlation between the number of B. rapa weed-specific AFLP markers and seed yield (r = 0.70, P = 0.0001), although no such correlation was detected for vegetative biomass. When genetic load was directly incorporated into the hybrid genome, by inserting a fitness-mitigating dwarfing gene that that is beneficial for crops but deleterious for weeds (a transgene mitigation measure), there was a dramatic decrease in the number of transgenic hybrid progeny persisting in the population. Conclusion The effects of genetic load of crop and in some situations, weed alleles might be beneficial under certain environmental conditions. However, when genetic load was directly incorporated into transgenic events, e.g., using a TM construct, the number of transgenic hybrids and persistence in weedy genomic backgrounds was significantly decreased

Genetic load and transgenic mitigating genes in transgenic Brassica rapa (field mustard) × Brassica napus (oilseed rape) hybrid populations

<p>Abstract</p> <p>Background</p> <p>One theoretical explanation for the relatively poor performance of <it>Brassica rapa </it>(weed) × <it>Brassica napus </it>(crop) transgenic hybrids suggests that hybridization imparts a negative genetic load. Consequently, in hybrids genetic load could overshadow any benefits of fitness enhancing transgenes and become the limiting factor in transgenic hybrid persistence. Two types of genetic load were analyzed in this study: random/linkage-derived genetic load, and directly incorporated genetic load using a transgenic mitigation (TM) strategy. In order to measure the effects of random genetic load, hybrid productivity (seed yield and biomass) was correlated with crop- and weed-specific AFLP genomic markers. This portion of the study was designed to answer whether or not weed × transgenic crop hybrids possessing more crop genes were less competitive than hybrids containing fewer crop genes. The effects of directly incorporated genetic load (TM) were analyzed through transgene persistence data. TM strategies are proposed to decrease transgene persistence if gene flow and subsequent transgene introgression to a wild host were to occur.</p> <p>Results</p> <p>In the absence of interspecific competition, transgenic weed × crop hybrids benefited from having more crop-specific alleles. There was a positive correlation between performance and number of <it>B. napus </it>crop-specific AFLP markers [seed yield vs. marker number (r = 0.54, P = 0.0003) and vegetative dry biomass vs. marker number (r = 0.44, P = 0.005)]. However under interspecific competition with wheat or more weed-like conditions (i.e. representing a situation where hybrid plants emerge as volunteer weeds in subsequent cropping systems), there was a positive correlation between the number of <it>B. rapa </it>weed-specific AFLP markers and seed yield (r = 0.70, P = 0.0001), although no such correlation was detected for vegetative biomass. When genetic load was directly incorporated into the hybrid genome, by inserting a fitness-mitigating dwarfing gene that that is beneficial for crops but deleterious for weeds (a transgene mitigation measure), there was a dramatic decrease in the number of transgenic hybrid progeny persisting in the population.</p> <p>Conclusion</p> <p>The effects of genetic load of crop and in some situations, weed alleles might be beneficial under certain environmental conditions. However, when genetic load was directly incorporated into transgenic events, e.g., using a TM construct, the number of transgenic hybrids and persistence in weedy genomic backgrounds was significantly decreased.</p

Transgenic Plants and Biosafety: Science, Misconceptions and Public Perceptions

One usually thinks of plant biology as a non-controversial topic, but the concerns raised over the biosafety of genetically modified (GM) plants have reached disproportionate levels relative to the actual risks. While the technology of changing the genome of plants has been gradually refined and increasingly implemented, the commercialization of GM crops has exploded. Today’s commercialized transgenic plants have been produced using Agrobacterium tumefaciens-mediated transformation or gene gun-mediated transformation. Recently, incremental improvements of biotechnologies, such as the use of green fluorescent protein (GFP) as a selectable marker, have been developed. Non-transformation genetic modification technologies such as chimeraplasty will be increasingly used to more precisely modify germplasm. In spite of the increasing knowledge about genetic modification of plants, concerns over ecological and food biosafety have escalated beyond scientific rationality. While several risks associated with GM crops and foods have been identified, the popular press, spurred by colorful protest groups, has left the general public with a sense of imminent danger. Reviewed here are the risks that are currently under research. Ecological biosafety research has identified potential risks associated with certain crop/transgene combinations, such as intra- and interspecific transgene flow, persistence and the consequences of transgenes in unintended hosts. Resistance management strategies for insect resistance transgenes and non-target effects of these genes have also been studied. Food biosafety research has focused on transgenic product toxicity and allergenicity. However, an estimated 3.5′ 1012 transgenic plants have been grown in the U.S. in the past 12 years, with over two trillion being grown in 1999 and 2000 alone. These large numbers and the absence of any negative reports of compromised biosafety indicate that genetic modification by biotechnology poses no immediate or significant risks and that resulting food products from GM crops are as safe as foods from conventional varieties. We are increasingly convinced that scientists have a duty to conduct objective research and to effectively communicate the results—especially those pertaining to the relative risks and potential benefits—to scientists first and then to the public. All stakeholders in the technology need more effective dialogues to better understand risks and benefits of adopting or not adopting agricultural biotechnologies