Physiological responses related to increased grain yield under drought in the first biotechnology-derived drought-tolerant maize.

Maize (Zea mays ssp. mays L.) is highly susceptible to drought stress. This work focused on whole-plant physiological mechanisms by which a biotechnology-derived maize event expressing bacterial cold shock protein B (CspB), MON 87460, increased grain yield under drought. Plants of MON 87460 and a conventional control (hereafter 'control') were tested in the field under well-watered (WW) and water-limited (WL) treatments imposed during mid-vegetative to mid-reproductive stages during 2009-2011. Across years, average grain yield increased by 6% in MON 87460 compared with control under WL conditions. This was associated with higher soil water content at 0.5 m depth during the treatment phase, increased ear growth, decreased leaf area, leaf dry weight and sap flow rate during silking, increased kernel number and harvest index in MON 87460 than the control. No consistent differences were observed under WW conditions. This indicates that MON 87460 acclimated better under WL conditions than the control by lowering leaf growth which decreased water use during silking, thereby eliciting lower stress under WL conditions. These physiological responses in MON 87460 under WL conditions resulted in increased ear growth during silking, which subsequently increased the kernel number, harvest index and grain yield compared to the control.

Microarray analyses of the metabolic responses of Saccharomyces cerevisiae to organic solvent dimethyl sulfoxide.

The toxic effects that organic solvents have on whole cells are important drawbacks in the application of these solvents in the production of fine chemicals by whole-cell stereoselective biotransformations. Although early studies found that organic solvents mainly destroyed the integrity of cell membranes by accumulating in the lipid bilayer of plasma membranes, the cellular metabolic responses to the presence of an organic solvent remain unclear. With the rapid development of genomics, it is possible to study cellular metabolism under perturbed conditions at the genome level. In this paper, the global gene expression profiles of Saccharomyces cerevisiae BY4743 grown in media with a high concentration of the organic solvent dimethyl sulfoxide (DMSO) were determined by microarray analysis of ~6,200 yeast open reading frames (ORFs). From cells grown in SD minimal medium containing 1.0% (v/v) DMSO, changes in transcript abundance greater than or equal to 2.5-fold were classified. Genomic analyses showed that 1,338 genes were significantly regulated by the presence of DMSO in yeast. Among them, only 400 genes were previously found to be responsive to general environmental stresses, such as temperature shock, amino acid starvation, nitrogen source depletion, and progression into stationary phase. The DMSO-responsive genes were involved in a variety of cellular functions, including carbohydrate, amino acid and lipid metabolism, cellular stress responses, and energy metabolism. Most of the genes in the lipid biosynthetic pathways were down-regulated by DMSO treatment, whereas genes involved in amino acid biosynthesis were mostly up-regulated. The results demonstrate that the application of microarray technology allows better interpretation of metabolic responses, and the information obtained will be useful for the construction of engineered yeast strains with better tolerance of organic solvents.

Global nutritional profiling for mutant and chemical mode-of-action analysis in filamentous fungi.

We describe a method for gene function discovery and chemical mode-of-action analysis via nutrient utilization using a high throughput Nutritional Profiling platform suitable for filamentous microorganisms. We have optimized the growth conditions for each fungal species to produce reproducible optical density growth measurements in microtiter plates. We validated the Nutritional Profiling platform using a nitrogen source utilization assay to analyze 21 Aspergillus nidulans strains with mutations in the master nitrogen regulatory gene, areA. Analysis of these data accurately reproduced expected results and provided new data to demonstrate that this platform is suitable for fine level phenotyping of filamentous fungi. Next, we analyzed the differential responses of two fungal species to a glutamine synthetase inhibitor, illustrating chemical mode-of-action analysis. Finally, a comparative phenotypic study was performed to characterize carbon catabolite repression in four fungal species using a carbon source utilization assay. The results demonstrate differentiation between two Aspergillus species and two diverse plant pathogens and provide a wealth of new data on fungal nutrient utilization. Thus, these assays can be used for gene function and chemical mode-of-action analysis at the whole organism level as well as interspecies comparisons in a variety of filamentous fungi. Additionally, because uniform distribution of growth within wells is maintained, comparisons between yeast and filamentous forms of a single organism can be performed.