Loss of CpSRP54 function leads to a truncated light-harvesting antenna size in Chlamydomonas reinhardtii

The Chlamydomonas reinhardtii truncated light-harvesting antenna 4 (tla4) DNA transposon mutant has a pale green phenotype, a lower chlorophyll (Chl) per cell and a higher Chl a/b ratio in comparison with the wild type. It required a higher light intensity for the saturation of photosynthesis and displayed a greater per chlorophyll light-saturated rate of oxygen evolution than the wild type. The Chl antenna size of the photosystems in the tla4 mutant was only about 65% of that measured in the wild type. Molecular genetic analysis revealed that a single plasmid DNA insertion disrupted two genes on chromosome 11 of the mutant. A complementation study identified the “chloroplast signal recognition particle 54” gene (CpSRP54), as the lesion causing the tla4 phenotype. Disruption of this gene resulted in partial failure to assemble and, therefore, lower levels of light-harvesting Chl-binding proteins in the C. reinhardtii thylakoids. A comparative in silico 3-D structure-modeling analysis revealed that the M-domain of the CpSRP54 of C. reinhardtii possesses a more extended finger loop structure, due to different amino acid composition, as compared to that of the Arabidopsis CpSRP54. The work demonstrated that CpSRP54 deletion in microalgae can serve to generate tla mutants with a markedly smaller photosystem Chl antenna size, improved solar energy conversion efficiency, and photosynthetic productivity in high-density cultures under bright sunlight conditions.     

Glycosylation profile and biological activity of Remicade® compared with Flixabi® and Remsima®

As biosimilars enter the market, comparisons of product quality are needed. Manufacturing differences may lead to differences in critical quality attributes, which affect efficacy. Therefore, critical quality attributes (structure and biological activity) of Remicade® and of 2 biosimilar products (Flixabi®/Renflexis® and Remsima®/Inflectra®) were determined. We assessed binding to tumor necrosis factor in a fluorescence competitive binding assay; potency in a luciferase reporter gene assay; percentages of galactosylated glycan, afucose plus high mannosylated glycans, and charged glycan; FcγRIIIa (CD16) binding (assessed by 3 methods); and antibody-dependent cell-mediated cytotoxicity (ADCC) in the NK92-CD16a cell line and in peripheral blood mononuclear cells (PBMC). The results of Fab-related activity were similar for all products. Compared with Remicade®, Flixabi® had a lower percentage of charged glycan, and Remsima® had a higher percentage of galactosylated glycan and a lower percentage of afucose plus high mannosylated glycans. Whereas Remsima® and Remicade® are expressed in a Sp2/0 cell line, Flixabi® is expressed in a CHO cell line. Despite this difference, galactosylated glycans from the 3 products were not correlated with the expression system. The results of all 3 methods used in this study indicated that FcγRIIIa binding was lower with Remsima® than with Remicade®. The percentage of ADCC in NK92-CD16a cells was lower with Remsima® and higher with Flixabi® compared with Remicade®, but was similar for all 3 products in PBMC. Surface expression of CD16 was 5.7-fold greater on NK92-CD16a cells than on PBMC. Combined percentages of afucosylated and high mannosylated glycans were positively correlated with FcγRIIIa binding and ADCC in NK92-CD16 cells, while no correlation was observed in PBMC.     

Human-mediated processes affecting distribution and genetic structure of Squalidus multimaculatus,a freshwater cyprinid with small spatial range

Endemic species typically have a narrow niche breadth, and are likely more vulnerable to extinction than more widespread taxa. Squalidus multimaculatus is a small cyprinid endemic to the Korean Peninsula, and its reported geographical range was restricted to several small rivers located along the southeast coast. Several populations of S. multimaculatus have supposedly been subject to a variety of recent anthropogenic actions. Here, we analyzed the pattern of genetic diversity within and among populations of S. multimaculatus using nine microsatellite loci to quantify the relative contributions of human-mediated processes to the contemporary distribution and genetic structure. Overall, low levels of genetic diversity were exhibited in the populations of S. multimaculatus. Genetic differentiations among populations were not completely represented by their geographical proximity, likely resulting from the low intrapopulation genetic variability and anthropogenic transplants. The most conspicuous outcome of the anthropogenic activities was the introgression of alleles from a closely related species, S. gracilis majimae. Our study showed that anthropogenic transplanting, even with only a small number of individuals, can challenge our conservation goal to maintain the species integrity that has long been shaped in evolutionary processes.