Evaluation of sugarcane (Saccharum officinarum L.) somaclonal variants tolerance to salinity in vitro and in vivo cultures

Tissue culture technique was used to obtain salt tolerant variants from embryogenic calli of sugarcane (Saccharum sp. Var. CP48-103) that were cultured on a selective medium containing different levels of NaCl (0, 33, 66, 99 and 132 mM). A total of four plants which regenerated from the tolerant calli were selected but the best in vigor were grown in in vitro and hydroponic systems under salinity stress (with the previous levels) as compared to source variety. With increasing supply of NaCl in both systems, root growth was more adversely affected than shoot growth. Chlorophyll contents showed a decreasing trend and dry matter yield of plants reduced but in a slow rate in tolerant somaclone than source variety. The tissues analysis showed that at high salt concentration, Cl- and Na+ content in shoot and root increased. With rising salt concentration from 0 to 132 mM, content of Cl- in shoot and root of tolerant variant changed and was lower than the parent. In conclusion, this variant probably had lowest genetic ratio of shoot: root chloride due to minimum transport of Cl- from the root to shoot. Also this variant had high content of Ca2+ in shoot and high K+/Na+ ratio at all salinity levels. Thus, it probably has genetic potential to avoid harmful ions accumulation.Key words: Sugarcane, salinity, somaclonal variation, in vivo, in vitro

Effect of promoter strength and signal sequence on the periplasmic expression of human interferon- &#9452b in Escherichia coli

Two plasmids, pFLAG-ATS and pET 26b(+), were studied for the periplasmic expression of recombinant human interferon-2b (IFN-2b) in Escherichia coli. The pFLAG-ATS contains ompA signal sequence and tac promoter while pET 26b(+) contains pelB signal sequence and T7lac promoter. It was observedthat periplasmic expression of IFN-2b from pET 26b(+) was around 3000 times higher than pFLAGATS. Difference in the expression level was attributed to the difference in the promoters and the signal sequences. In silico analysis of mRNA secondary structures were analyzed using Vienna RNA packageand MFOLD. The results suggested that the increase of expression would mainly due to the difference in the translation initiation associated with secondary structure of mRNA transcribed by both plasmids

Maps of open chromatin highlight cell type-restricted patterns of regulatory sequence variation at hematological trait loci

<p>Nearly three-quarters of the 143 genetic signals associated with platelet and erythrocyte phenotypes identified by meta-analyses of genome-wide association (GWA) studies are located at non-protein-coding regions. Here, we assessed the role of candidate regulatory variants associated with cell type-restricted, closely related hematological quantitative traits in biologically relevant hematopoietic cell types. We used formaldehyde-assisted isolation of regulatory elements followed by next-generation sequencing (FAIRE-seq) to map regions of open chromatin in three primary human blood cells of the myeloid lineage. In the precursors of platelets and erythrocytes, as well as in monocytes, we found that open chromatin signatures reflect the corresponding hematopoietic lineages of the studied cell types and associate with the cell type-specific gene expression patterns. Dependent on their signal strength, open chromatin regions showed correlation with promoter and enhancer histone marks, distance to the transcription start site, and ontology classes of nearby genes. Cell type-restricted regions of open chromatin were enriched in sequence variants associated with hematological indices. The majority (63.6%) of such candidate functional variants at platelet quantitative trait loci (QTLs) coincided with binding sites of five transcription factors key in regulating megakaryopoiesis. We experimentally tested 13 candidate regulatory variants at 10 platelet QTLs and found that 10 (76.9%) affected protein binding, suggesting that this is a frequent mechanism by which regulatory variants influence quantitative trait levels. Our findings demonstrate that combining large-scale GWA data with open chromatin profiles of relevant cell types can be a powerful means of dissecting the genetic architecture of closely related quantitative traits.</p>