Transgenic restorer rice line T1c-19 with stacked cry1C*/bar genes has low weediness potential without selection pressure

Stacked（insect and herbicide resistant） transgenic rice T1c-19 with cry1C＊/bar genes, its receptor rice Minghui 63（herein MH63） and a local two-line hybrid indica rice Fengliangyou Xiang 1（used as a control） were compared for agronomic performance under field conditions without the relevant selection pressures. Agronomic traits（plant height, tiller number, and aboveground dry biomass）, reproductive ability（pollen viability, panicle length, and filled grain number of main panicles, seed set, and grain yield）, and weediness characteristics（seed shattering, seed overwintering ability, and volunteer seedling recruitment） were used to assess the potential weediness without selection pressure of stacked transgene rice T1c-19. In wet direct-seeded and transplanted rice fields, T1c-19 and its receptor MH63 performed similarly regarding vegetative growth and reproductive ability, but both of them were significantly inferior to the control. T1c-19 did not display weed characteristics; it had weak overwintering ability, low seed shattering and failed to establish volunteers. Exogenous insect and herbicide resistance genes did not confer competitive advantage to transgenic rice T1c-19 grown in the field without the relevant selection pressures.

Developing transgenic maize(Zea mays L.) with insect resistance and glyphosate tolerance by fusion gene transformation

Using linker peptide LP4/2A for multiple gene transformation is considered to be an effective method to stack or pyramid several traits in plants. Bacillus thuringiensis（Bt） cry gene and epsps（5-enolpyruvylshikimate-3-phosphate synthase） gene are two important genes for culturing pest-resistant and glyphosate-tolerant crops. We used linker peptide LP4/2A to connect the Bt cry1 Ah gene with the 2m G2-epsps gene and combined the wide-used man A gene as a selective marker to construct one coordinated expression vector called p2 EPUHLAGN. The expression vector was transferred into maize by Agrobacterium tumefaciens-mediated transformation, and 60 plants were obtained, 40% of which were positive transformants. Molecular detection demonstrated that the two genes in the fusion vector were expressed simultaneously and spliced correctly in translation processing; meanwhile bioassay detection proved the transgenic maize had preferable pest resistance and glyphosate tolerance. Therefore, linker peptide LP4/2A provided a simple and reliable strategy for producing gene stacking in maize and the result showed that the fusion gene transformation system of LP4/2A was feasible in monocot plants.

Transgene Stacking in Cotton Improvement

To date,more and more transgenic varieties of upland cotton(Gossypium hirsutum L.) generated with transgenes,which derived from varies of alien species,are playing important role in agricultural production.Stacking of multi-transgenes has a potential for combining all the merits of

Plant Synthetic Metabolic Engineering for Enhancing Crop Nutritional Quality

Nutrient deficiencies in crops are a serious threat to human health,especially for populations in poor areas.To overcome this problem,the development of crops with nutrient-enhanced traits is imperative.Biofortification of crops to improve nutritional quality helps combat nutrient deficiencies by increasing the levels of specific nutrient components.Compared with agronomic practices and conventional plant breeding,plant metabolic engineering and synthetic biology strategies are more effective and accurate in synthesizing specific micronutrients,phytonutrients,and/or bioactive components in crops.In this review,we discuss recent progress in the field of plant synthetic metabolic engineering,specifically in terms of research strategies of multigene stacking tools and engineering complex metabolic pathways,with a focus on improving traits related to micronutrients,phytonutrients,and bioactive components.Advances and innovations in plant synthetic metabolic engineering would facilitate the development of nutrient-enriched crops to meet the nutritional needs of humans.

Costs of resistance to fungal pathogens in genetically modified wheat

Aims Many resistance genes against fungal pathogens show costs of resistance.Genetically modified(GM)plants that differ in only one or a few resistance genes from control plants present ideal systems for measuring these costs in the absence of pathogens.Methods To assess the ecological relevance of costs of pathogen resistance,we grew individual plants of four transgenic spring wheat lines in a field trial with three pathogen levels and varied the genetic diversity of the crop.Important Findings We found that two lines with a Pm3b transgene were more resistant to powdery mildew than their sister lines of the variety Bobwhite,whereas lines with chitinase(A9)or chitinase and glucanase(A13)transgenes were not more resistant than their mother variety Frisal.Nevertheless,in the absence of the pathogen,both the GM lines of Bobwhite as well as those of Frisal performed significantly worse than their controls,i.e.Pm3b#1 and Pm3b#2 had 39%or 53%and A9 and A13 had 14%or 23%lower yields.In the presence of the pathogen,all GM lines except Pm3b#2 could increase their yields and other fitness-related traits,reaching the performance levels of the control lines.Line Pm3b#2 seemed to have lost its phenotypic plasticity and had low performance in all environments.This may have been caused by very high transgene expression.No synergistic effects of mixing different GM lines with each other were detected.This might have been due to high transgene expression or the similarity between the lines regarding their resistance genes.We conclude that costs of resistance can be high for transgenic plants with constitutive transgene expression and that this can occur even in cases where the non-transgenic control lines are already relatively resistant,such as in our variety Frisal.Transgenic plants could only compete with conventional varieties in environments with high pathogen pressure.Furthermore,the large variability among the GM lines,which may be due to unpredictable transgene expression,suggests that case-by-case assessments are necessary to evaluate costs of resistance.