AtNusG, a chloroplast nucleoid protein of bacterial origin linking chloroplast transcriptional and translational machineries, is required for proper chloroplast gene expression in Arabidopsis thaliana.

In Escherichia coli, transcription-translation coupling is mediated by NusG. Although chloroplasts are descendants of endosymbiotic prokaryotes, the mechanism underlying this coupling in chloroplasts remains unclear. Here, we report transcription-translation coupling through AtNusG in chloroplasts. AtNusG is localized in chloroplast nucleoids and is closely associated with the chloroplast PEP complex by interacting with its essential component PAP9. It also comigrates with chloroplast ribosomes and interacts with their two components PRPS5 (uS5c) and PRPS10 (uS10c). These data suggest that the transcription and translation machineries are coupled in chloroplasts. In the atnusg mutant, the accumulation of chloroplast-encoded photosynthetic gene transcripts, such as psbA, psbB, psbC and psbD, was not obviously changed, but that of their proteins was clearly decreased. Chloroplast polysomic analysis indicated that the decrease in these proteins was due to the reduced efficiency of their translation in this mutant, leading to reduced photosynthetic efficiency and enhanced sensitivity to cold stress. These data indicate that AtNusG-mediated coupling between transcription and translation in chloroplasts ensures the rapid establishment of photosynthetic capacity for plant growth and the response to environmental changes. Therefore, our study reveals a conserved mechanism of transcription-translation coupling between chloroplasts and E. coli, which perhaps represents a regulatory mechanism of chloroplast gene expression. This study provides insights into the underlying mechanisms of chloroplast gene expression in higher plants.

AtRsmD Is Required for Chloroplast Development and Chloroplast Function in Arabidopsis thaliana.

AtRsmD was recently demonstrated to be a chloroplast 16S rRNA methyltransferase (MTase) for the m2G915 modification in Arabidopsis. Here, its function of AtRsmD for chloroplast development and photosynthesis was further analyzed. The AtRsmD gene is highly expressed in green photosynthetic tissues. AtRsmD is associated with the thylakoid in chloroplasts. The atrsmd-2 mutant exhibited impaired photosynthetic efficiency in emerging leaves under normal growth conditions. A few thylakoid lamellas could be observed in the chloroplast from the atrsmd-2 mutant, and these thylakoids were loosely organized. Knockout of the AtRsmD gene had minor effects on chloroplast ribosome biogenesis and RNA loading on chloroplast ribosomes, but it reduced the amounts of chloroplast-encoded photosynthesis-related proteins in the emerging leaves, for example, D1, D2, CP43, and CP47, which reduced the accumulation of the photosynthetic complex. Nevertheless, knockout of the AtRsmD gene did not cause a general reduction in chloroplast-encoded proteins in Arabidopsis grown under normal growth conditions. Additionally, the atrsmd-2 mutant exhibited more sensitivity to lincomycin, which specifically inhibits the elongation of nascent polypeptide chains. Cold stress exacerbated the effect on chloroplast ribosome biogenesis in the atrsmd-2 mutant. All these data suggest that the AtRsmD protein plays distinct regulatory roles in chloroplast translation, which is required for chloroplast development and chloroplast function.

Influence of Vitamin A deficiency on the transcriptomic profile of rat meibomian glands.

PURPOSE: Vitamin A deficiency (VAD) is associated with chalazion in young children. However, the underlying molecular mechanism remains unclear. In the present study, transcriptome data from rat meibomian glands (MGs) were analyzed to reveal specific molecular responses to VAD. METHODS: Total RNA was extracted and purified for library preparation and transcriptome sequencing. Differentially expressed genes (DEGs) between vitamin A normal (VAN) and VAD rats were analyzed using DESeq software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of DEGs were performed using the GO seq R package and KOBAS software. Real-time quantitative reverse transcription polymerase chain reaction was used to validate the RNA sequencing results. RESULTS: The number of DEGs in the VAD group compared to the VAN group was 3129 (1531 upregulated and 1598 downregulated) in the rat MGs. VAD upregulated a large number of lipid metabolism-related genes. GO analysis showed that the most enriched and meaningful terms were related to lipid metabolism (e.g., "oxidation-reduction process, GO: 0,055,114," "lipid metabolic process, GO: 000,662"). KEGG pathway analysis showed that most of the enriched signaling pathways were involved in lipid metabolism, including the PPAR signaling pathway associated with retinoic acid (RA)-mediated nuclear receptors. CONCLUSION: These findings demonstrate that VAD regulates the expression of numerous genes in the rat MG and that many of these genes are involved in lipid metabolic pathways.

[Expression Level of FLRG in Colon Cancer Tissue and Its Clinical Significance].

OBJECTIVE: To investigate the expression of follistatin related gene ( FLRG) in colon cancer and its relationship with clinicopathological features of colon cancer. METHODS: The cancer tissue, paracancerous tissue and normal tissue were collected from 80 patients with colon cancer who underwent radical operation from December 2018 to December 2019. Immunohistochemistry and Real-time PCR were carried out to examine the expression of FLRG and the clinical implications of FLRG was further analyzed. RESULTS: The expression of FLRG in colon cancer tissues was significantly higher than that in paracancerous tissues and normal tissues ( P<0.05), and the expression of FLRG in paracancerous tissues was significantly higher than that in normal tissues ( P<0.05). There was no significant difference in the expression of FLRG among colon cancer patients with different sex, age, tumor growth location and differentiation degree ( P>0.05). The expression level of FLRG in patients with distant metastasis was higher than that in patients without distant metastasis ( P<0.05), and the expression level of FLRG in patients with late clinical stage (stage Ⅲ and Ⅳ) was higher than that in patients with earlier clinical stage (stage Ⅰ and Ⅱ) ( P<0.05). CONCLUSION: FLRG is up-regulated in colon cancer tissue, which may be involved in the regulation of tumor development. FLRG may be a potential prognostic target.

mTERF8, a Member of the Mitochondrial Transcription Termination Factor Family, Is Involved in the Transcription Termination of Chloroplast Gene psbJ.

Members of the mitochondrial transcription terminator factor (mTERF) family, originally identified in vertebrate mitochondria, are involved in the termination of organellular transcription. In plants, mTERF proteins are mainly localized in chloroplasts and mitochondria. In Arabidopsis (Arabidopsis thaliana), mTERF8/pTAC15 was identified in the plastid-encoded RNA polymerase (PEP) complex, the major RNA polymerase of chloroplasts. In this work, we demonstrate that mTERF8 is associated with the PEP complex. An mTERF8 knockout line displayed a wild-type-like phenotype under standard growth conditions, but showed impaired efficiency of photosystem II electron flow. Transcription of most chloroplast genes was not substantially affected in the mterf8 mutant; however, the level of the psbJ transcript from the psbEFLJ polycistron was increased. RNA blot analysis showed that a larger transcript accumulates in mterf8 than in the wild type. Thus, abnormal transcription and/or RNA processing occur for the psbEFLJ polycistron. Circular reverse transcription PCR and sequence analysis showed that the psbJ transcript terminates 95 nucleotides downstream of the translation stop codon in the wild type, whereas its termination is aberrant in mterf8 Both electrophoresis mobility shift assays and chloroplast chromatin immunoprecipitation analysis showed that mTERF8 specifically binds to the 3' terminal region of psbJ Transcription analysis using the in vitro T7 RNA polymerase system showed that mTERF8 terminates psbJ transcription. Together, these results suggest that mTERF8 is specifically involved in the transcription termination of the chloroplast gene psbJ.

[Effect of mono and combination therapy with FTY720 and ICAM-1 mAb for mouse-to-rat cardiac xenotransplantation].

OBJECTIVE: To observe the effect of FTY720 and ICAM-1 mAb mono and combination therapy in mouse-to-rat cardiac xenotransplantation. METHODS: Cardiac xenotransplantation was performed in abdominal site with micro-surgical technique. Recipients with xenografts were treated with different doses of FTY720 and/or ICAM-1 mAb. Graft survival, histopathology, infiltration of CD4+, and CD8+ T cells and levels of serum IL-2, IFN-gamma, IL-4, and IgM were investigated. RESULTS: Survival time of xenografts was (2.75+/- 0.43)d in the controls, survival of grafts treated with ICAM-1 mAb did not significantly improve. Treatment with large dose FTY720 led to a survival of (4.25+/- 0.71)d (P<0.01). Combination therapy with large dose FTY720 and ICAM-1 mAb achieved a significant prolongation of graft survival with (10.25+/- 2.12)d (P<0.01). Levels of serum IL-2, IFN-gamma and rat-anti-mouse IgM decreased in the combined therapy group. Pathologic lesion and infiltration of T cells in xenografts showed mitigated in the large dose combined therapy group. There was a significant negative correlation between the antibody level and the graft survival time (R=-0.754, P<0.01). CONCLUSION: The combined therapy of FTY720 and ICAM-1 mAb can achieve a significant effect in the prolongation of heart xenograft survival and inhibition of xenoantibodies.

[Immune tolerance induced by combined heart-thymus transplantation for heart allograft in rats].

OBJECTIVE: To explore the role of combined heart-thymus transplantation for heart allograft in rats. METHODS: Vascularized heart-thymus combined transplantation was performed with microsurgical technique. Graft survival, histopathology, infiltration of CD4+, CD8+ T cells, level and mRNA expressions of IL-2 and IL-4 in the serum and cardiac grafts were investigated. RESULTS: Heart allograft in the controls had a survival time of (6.0+/-0.76) d. heart-thymus combined transplantation in non-thymectomized rats had a survival time of (6.88+/-0.64)d (P<0.05). Heart-thymus combined transplantation in thymectomized rats led to an evident survival time of (14.13+/-5.82)d (P<0.01) for cardiac graft, which further obtained long term survival after short course of treatment with cyclosporine. Pathologic lesion and infiltration of CD4+ and CD8+ T cells in cardiac grafts showed mitigated in the long term survival group. IL-2 level in the serum and cardiac grafts maintained low level in the long term survival group, whereas IL-4 maintained high level. CONCLUSION: Whether thymectomized or not in recipient rats, heart-thymus combined transplantation has a positive effect to protect cardiac graft. Furthermore, in thymectomized rats heart-thymus combined transplantation may lead to evident survival prolongation of the heart grafts, which induces immune tolerance in short course of treatment with cyclosporine.

[Immune tolerance induced by combined heart-thymus transplantation with intrathymic inoculation of thymocytes in rats].

OBJECTIVE: To explore the role of allo heart and thymus transplantation by intrathymic inoculation of thymocytes. METHODS: Wistar recipients were given intrathymic injection of allo thymocytes (2 x 10(7)) 14 days before the heart and/or thymus transplantation. Graft survival, histopathology, levels and mRNA expressions of IL-2, IL-4 in serum and cardiac-grafts were investigated. RESULTS: Heart transplantation and heart-thymus composite transplantation with the treatment of CysA for 7 or 14 days prolonged graft survival. Heart transplantation and heart-thymus composite transplantation with intrathymic thymocytes injection induced the long-term survival of allo-grafts transiently immunosuppressed with CysA; IL-4 maintained at high levels but IL-2 kept at low levels in grafts in long-term survivals. CONCLUSION: Intrathymic inoculation of allo thymoctyes can induce immune tolerance for both cardiac transplantation and heart-thymus combined transplantation in rats. Thymus graft may play a role in the induction and maintenance of central tolerance.

[Effect of cyclosporine and simulect mono and combination therapy on cardiac allo-transplantation in rats].

OBJECTIVE: To observe the effect of cyclosporine and simulect mono or combination therapy on cardiac allo-transplantation in rats. METHODS: Recipients with allografts were treated with different doses of cyclosporine and/or simulect after cardiac allo-transplantation. Graft survival time was observed; the histopathological examination of graft tissues was performed; and levels of serum IL-2 and IL-4 were determined. RESULTS: Mono or combination therapy with cyclosporine and/or simulect increased the survival of cardiac allografts. With the prolongation of survival time of the grafts, the rejection of grafts was moderated. The serum IL-2 level increased in acute rejected grafts; the serum IL-4 level increased evidently in long survival grafts. CONCLUSION: Cyclosporine and simulect have an effect in the prolongation of cardiac allograft survival in rats, and the combination therapy shows an evident synergistic effect.