Differentiation of naïve B cells, including immunoglobulin (Ig) class switch DNA recombination (CSR), is critical for the immune response and depends on the extensive integration of signals from the B cell receptor (BCR), tumor necrosis factor (TNF) receptor family members, Toll-like receptors (TLRs) and cytokine receptors. TLRs and BCR synergize to induce CSR in T cell-dependent and T cell-independent antibody responses to microbial pathogens. BCR triggering together with simultaneous endosomal TLR engagement leads to enhanced B cell differentiation and antibody responses. The requirement of both BCR and TLR engagement would ensure appropriate antigen-specific activation in an infection. Co-stimulation of TLRs and BCR likely plays a significant role in anti-microbial antibody responses to contain pathogen loads until the T cell-dependent antibody responses peak. Furthermore, the temporal sequence of different signals is also critical for optimal B cell responses, as exemplified by the activation of B cells by initial TLR engagement, leading to the upregulation of co-stimulatory CD80 and MHC-II receptors, which, in turn, result in more efficient interactions with T cells, thereby enhancing the germinal center (GC) reaction and antibody affinity maturation. Overall, BCR and TLR stimulation and the integration with signals from the pathogen or immune cells and their products, determine the ensuing B cell antibody response.

These authors contributed equally to this work. SUMMARYDespite significant progress in clarifying the subunit compositions and functions of the multiple NADPH dehydrogenase (NDH-1) complexes in cyanobacteria, the subunit maturation and assembly of their NDH-1 complexes are poorly understood. By transformation of wild-type cells with a transposon-tagged library, we isolated three mutants of Synechocystis sp. PCC 6803 defective in NDH-1-mediated cyclic electron transfer and unable to grow under high light conditions. All the mutants were tagged in the same slr1097 gene, encoding an unknown protein that shares significant homology with the Arabidopsis protein chlororespiratory reduction 6 (CRR6). The slr1097 product was localized in the cytoplasm and was required for efficient assembly of NDH-1 complexes. Analysis of the interaction of Slr1097 with 18 subunits of NDH-1 complexes using a yeast two-hybrid system indicated a strong interaction with NdhI but not with other Ndh subunits. Absence of Slr1097 resulted in a significant decrease of NdhI in the cytoplasm, but not of other Ndh subunits including NdhH, NdhK and NdhM; the decrease was more evident in the cytoplasm than in the thylakoid membranes. In the Δslr1097 mutant, NdhH, NdhI, NdhK and NdhM were hardly detectable in the NDH-1M complex, whereas almost half the wild-type levels of these subunits were present in NDH-1L complex; similar results were observed in the NdhI-less mutant. These results suggest that Slr1097 is involved in the maturation of NdhI, and that assembly of the NDH-1M complex is strongly dependent on this factor. Maturation of NdhI appears not to be crucial to assembly of the NDH-1L complex.

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Background: There is no report on Ndh subunits that destabilize the NDH-1 complex and repress activity. Results: Deletion of ndhO in Synechocystis 6803 increased the activity of cyclic electron transport around photosystem I, whereas overexpression repressed the activity and destabilized NDH-1M complex. Conclusion: NdhO destabilizes NDH-1M and represses the activity. Significance: NdhO is a new type subunit that controls NDH-1M negatively.

Background: Two major NADPH dehydrogenase complexes, NDH-1L and NDH-1M, have been identified in cyanobacteria. Results: NdhP is localized in the NDH-1L complex, and absence of this subunit or its C-terminal tail disassembled NDH-1L to NDH-1M. Conclusion: C terminus of NdhP is essential to stabilize the NDH-1L complex. Significance: Our results provide novel insights into the assembly and stabilization of NDH-1L complex.

Ganoderma lucidum is a medicinal mushroom that is well known for its ability to enhance human health, and products made from this fungus have been highly profitable. The substrate-degrading ability of G. lucidum could be related to its growth. CAZy proteins were more abundant in its genome than in the other white rot fungi models. Among these CAZy proteins, changes in lignocellulolytic enzymes during growth have not been well studied. Using genomic, transcriptomic and secretomic analyses, this study focuses on the lignocellulolytic enzymes of G. lucidum strain G0119 to determine which of these degradative enzymes contribute to its growth. From the genome sequencing data, genes belonging to CAZy protein families, especially genes involved in lignocellulose degradation, were investigated. The gene expression, protein abundance and enzymatic activity of lignocellulolytic enzymes in mycelia over a growth cycle were analysed. The overall expression cellulase was higher than that of hemicellulase and lignin-modifying enzymes, particularly during the development of fruiting bodies. The cellulase and hemicellulase abundances and activities increased after the fruiting bodies matured, when basidiospores were produced in massive quantities till the end of the growth cycle. Additionally, the protein abundances of the lignin-modifying enzymes and the expression of their corresponding genes, including laccases and lignin-degrading heme peroxidases, were highest when the mycelia fully spread in the compost bag. Type I cellobiohydrolase was observed to be the most abundant extracellular lignocellulolytic enzyme produced by the G. lucidum strain G0119. The AA2 family haem peroxidases were the dominant lignin-modifying enzyme expressed during the mycelial growth phase, and several laccases might play roles during the formation of the primordium. This study provides insight into the changes in the lignocellulose degradation ability of G. lucidum during its growth and will facilitate the discovery of new approaches to accelerate the growth of G. lucidum in culture.

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