Project description:Photoperiod is a circannual signal measured by biological systems to align growth and reproduction with the seasons. To understand the effect of photoperiod of gene expression in Arabidopsis thaliana in the absence of exogenous sugar under constant light intensity, we performed time course mRNA-seq analysis on 13-day old seedlings across three photoperiods with triplicates to identify photoperiod-regulated genes.
Project description:To investigate the role of LLM-domain B-GATAs in starch metabolism we performed gene expression profiling analysis of RNA-seq data, obtained with Illumina technologies. B-GATA double mutant gnc gnl and the transgenic line overexpressing GNL were grown in dark conditions to avoid interference from photosynthesis or other light-dependent processes affecting sugar and starch biosynthesis.
Project description:The triose-phosphate/phosphate translocator (TPT) of the chloroplast inner envelope membrane mediates the counter-exchange of stromal triose phosphates derived from CO2 fixation with cytosolic phosphate, thus providing the cytosol with precursors for sucrose synthesis. We have isolated an Arabidopsis mutant (tpt-1) in which the gene encoding TPT is disrupted by a T-DNA insertion. During growth in low light tpt-1 plants are phenotypically normal, but in high light photosynthesis is inhibited and growth is retarded relative to wildtype. This mutant compensates for the absence of TPT by diverting photosynthate into starch which is hydrolysed and exported from the chloroplast as glucose that is subsequently phosphorylated by hexokinase. In low light the capacity of the pathway of starch synthesis is sufficient to accommodate the normal rate of CO2 fixation, but in high light it is unable to match the potential rate of CO2 fixation. Consequently, in high light-grown plants there are measurable effects on the redoxstate of several components. Thus, the tpt-1 mutation influences the carbohydrate status within the cell, alters the form in which carbon is received by the cytosol, and changes the redox signals that are important in photosynthetic acclimation. Method: Plants will be grown in a 8h light:16h dark regime at both 400 and 100 µmol PAR m-2 s-1. Total RNA will be extracted from pools of individual illuminated leaves from at least eight plants at growth stage 3.70. Leaves will be harvested 2 h into the photoperiod to maximise differences between plant lines in the expression of genes of photosynthesis and carbohydrate metabolism. We anticipate that expression of many genes will be affected by the absence of TPT and by changes in light intensity. However, by comparing differences in transcript levels between wildtype and TPT mutant grown in high light with the differences that occur in plants grown in low light we will discriminate between genes whose expression is affected by changes in the pattern of carbohydrate metabolism and those influenced by redox poise of the thylakoid photochemical components. These comparisons will also highlight genes affected by recently identified regulatory interactions between sugar-sensing and redox-sensing. A genome-wide expression study will establish the extent to which gene expression is altered by the absence of TPT in leaves, and will provide the basis for more detailed analysis of a selected range of transcripts whose levels of expression differ between plant lines.
Project description:The rate of improvement of sugar content in sugarcane remains low for decades worldwide. Our previous transcriptome studies provided an atlas of sucrose accumulation-related gene expression but little is known about proteins involved. Here this knowledge gap is addressed by a proteomic analysis of experimentally altered sucrose accumulation in sugarcane. Analysis of stem proteomes of ripener ethephon-treated high- and low-sugar genotypes had identified 2983 proteins of which 139 were significantly differentially expressed (DEPs). These DEPs were found to be involved in sugar metabolism-related processes with 25 of them may have a regulatory role in sucrose accumulation. The key proteins identified include UDP-glucose 6-dehydrogenase associated with amino sugar and nucleotide sugar metabolism; those involved in carbon fixation; and fructokinase, β-D-glucosidase and α-glucan phosphorylase involved in starch and sucrose metabolism. Distinct genotype- and ethephon-dependent DEP expression was evident providing new insights on one of the most intractable sugarcane traits to breeding.
Project description:Carbon fixation plays a central role in determining cellular redox poise, increasingly understood to be a key parameter in cyanobacterial physiology. In the cyanobacterium Prochlorococcus--—the most abundant phototroph in the oligotrophic oceans--—the carbon-concentrating mechanism (CCM) is reduced to the bare essentials. Given the ability of Prochlorococcus populations to grow under a wide range of oxygen concentrations in the ocean, we wondered how carbon and oxygen physiology intersect in this minimal phototroph. We monitored genome-wide transcription in cells shocked with acute limitation of CO2, O2, or both. O2 limitation produced much smaller transcriptional changes than the broad suppression seen under CO2 limitation and CO2/O2 co-limitation. Strikingly, the transcriptional responses evoked by both CO2 limitation conditions were initially similar to that previously seen in high light stress, but at later timepoints we observed O2-dependent recovery of photosynthesis-related transcripts. These results suggest that oxygen plays a protective role in Prochlorococcus when carbon fixation is not a sufficient sink for light energy.