Different lumen-targeting pathways for nuclear-encoded versus cyanobacterial/plastid-encoded Hcf136 proteins

AbstractLumenal proteins are transported across the thylakoid membrane by two very different pathways: Sec-dependent or twin-arginine translocase (Tat)-dependent, where the substrate protein can be transported in a folded state. We present the first evidence that a given protein can be targeted by different pathways in different organisms. Arabidopsis Hcf136 is targeted exclusively by the Tat pathway in pea chloroplasts and no Sec-dependent transport is evident even when the twin-arginine is replaced by twin-lysine. However, twin-arginine motifs are absent from the presequences of Hcf136 proteins encoded by plastid or cyanobacterial genomes, strongly implying translocation by another pathway (presumably Sec). We suggest that the Hcf136 protein was transferred to the Tat pathway when the gene became incorporated into the nuclear genome, possibly due to the tighter folding associated with the more involved, post-translational targeting pathway

Transcript profiles uncover temporal and stress-induced changes of metabolic pathways in germinating sugar beet seeds

<p>Abstract</p> <p>Background</p> <p>With a cultivation area of 1.75 Mio ha and sugar yield of 16.7 Mio tons in 2006, sugar beet is a crop of great economic importance in Europe. The productivity of sugar beet is determined significantly by seed vigour and field emergence potential; however, little is known about the molecular mechanisms underlying these traits. Both traits exhibit large variations within sugar beet germplasm that have been difficult to ascribe to either environmental or genetic causes. Among potential targets for trait improvement, an enhancement of stress tolerance is considered because of the high negative influence of environmental stresses on trait parameters. Extending our knowledge of genetic and molecular determinants of sugar beet germination, stress response and adaptation mechanisms would facilitate the detection of new targets for breeding crop with an enhanced field emergence potential.</p> <p>Results</p> <p>To gain insight into the sugar beet germination we initiated an analysis of gene expression in a well emerging sugar beet hybrid showing high germination potential under various environmental conditions. A total of 2,784 ESTs representing 2,251 'unigenes' was generated from dry mature and germinating seeds. Analysis of the temporal expression of these genes during germination under non-stress conditions uncovered drastic transcriptional changes accompanying a shift from quiescent to metabolically active stages of the plant life cycle. Assay of germination under stressful conditions revealed 157 genes showing significantly different expression patterns in response to stress. As deduced from transcriptome data, stress adaptation mechanisms included an alteration in reserve mobilization pathways, an accumulation of the osmoprotectant glycine betaine, late embryogenesis abundant proteins and detoxification enzymes. The observed transcriptional changes are supposed to be regulated by ABA-dependent signal transduction pathway.</p> <p>Conclusion</p> <p>This study provides an important step toward the understanding of main events and metabolic pathways during germination in sugar beet. The reported alterations of gene expression in response to stress shed light on sugar beet stress adaptation mechanisms. Some of the identified stress-responsive genes provide a new potential source for improvement of sugar beet stress tolerance during germination and field emergence.</p

Evolution of the C4 phosphoenolpyruvate carboxylase promoter of the C4 species Flaveria trinervia: the role of the proximal promoter region

<p>Abstract</p> <p>Background</p> <p>The key enzymes of photosynthetic carbon assimilation in C₄plants have evolved independently several times from C₃isoforms that were present in the C₃ancestral species. The C₄isoform of phosphoenolpyruvate carboxylase (PEPC), the primary CO₂-fixing enzyme of the C₄cycle, is specifically expressed at high levels in mesophyll cells of the leaves of C₄species. We are interested in understanding the molecular changes that are responsible for the evolution of this C₄-characteristic PEPC expression pattern, and we are using the genus <it>Flaveria </it>(Asteraceae) as a model system. It is known that <it>cis</it>-regulatory sequences for mesophyll-specific expression of the <it>ppcA1 </it>gene of <it>F. trinervia </it>(C₄) are located within a distal promoter region (DR).</p> <p>Results</p> <p>In this study we focus on the proximal region (PR) of the <it>ppcA1 </it>promoter of <it>F. trinervia </it>and present an analysis of its function in establishing a C₄-specific expression pattern. We demonstrate that the PR harbours <it>cis</it>-regulatory determinants which account for high levels of PEPC expression in the leaf. Our results further suggest that an intron in the 5' untranslated leader region of the PR is not essential for the control of <it>ppcA1 </it>gene expression.</p> <p>Conclusion</p> <p>The allocation of <it>cis</it>-regulatory elements for enhanced expression levels to the proximal region of the <it>ppcA1 </it>promoter provides further insight into the regulation of PEPC expression in C₄leaves.</p

Comparative genomic analysis of C4 photosynthetic pathway evolution in grasses

Comparison of the sorghum, maize and rice genomes shows that gene duplication and functional innovation is common to evolution of most but not all genes in the C4 photosynthetic pathwa

The TreaT-Assay: A Novel Urine-Derived Donor Kidney Cell-Based Assay for Prediction of Kidney Transplantation Outcome

Donor-reactive immunity plays a major role in rejection after kidney transplantation, but analysis of donor-reactive T-cells is not applied routinely. However, it has been shown that this could help to identify patients at risk of acute rejection. A major obstacle is the limited quantity or quality of the required allogenic stimulator cells, including a limited availability of donor-splenocytes or an insufficient HLA-matching with HLA-bank cells. To overcome these limitations, we developed a novel assay, termed the TreaT (Transplant reactive T-cells)-assay. We cultivated renal tubular epithelial cells from the urine of kidney transplant patients and used them as stimulators for donor-reactive T-cells, which we analyzed by flow cytometry. We could demonstrate that using the TreaT-assay the quantification and characterization of alloreactive T-cells is superior to other stimulators. In a pilot study, the number of pre-transplant alloreactive T-cells negatively correlated with the post-transplant eGFR. Frequencies of pre-transplant CD161+ alloreactive CD4+ T-cells and granzyme B producing alloreactive CD8+ T-cells were substantially higher in patients with early acute rejection compared to patients without complications. In conclusion, we established a novel assay for the assessment of donor-reactive memory T-cells based on kidney cells with the potential to predict early acute rejection and post-transplant eGFR