Global Landscape of Native Protein Complexes in Synechocystis sp. PCC 6803

Synechocystis sp. PCC 6803(hereafter: Synechocystis) is a model organism for studying photosynthesis, energy metabolism, and environmental stress. Although known as the first fully sequenced phototrophic organism, Synechocystis still has almost half of its proteome without functional annotations. In this study, by using co-fractionation coupled with liquid chromatographytandem mass spectrometry(LC-MS/MS), we define 291 multi-protein complexes, encompassing24,092 protein±protein interactions(PPIs...     

The Effect of Various Stresses on the Expression of Genes Encoding the Secreted Proteins of the Cyanobacterium Synechocystis sp. PCC 6803

The effects of various stresses (osmotic, salt, low-temperature, high-temperature, and high-light stress) on the amount of mRNA of eight genes encoding the secreted proteins of Synechocystis sp. PCC 6803 were studied. Osmotic stress (0.5 M sorbitol) reduced the amount of all mRNAs, with the exception of slr0924. Supposedly, this gene encodes Tic22, a polypeptide involved in the formation of the transport system for proteins crossing the internal thylakoid membrane on the way to the lumen. Salt stress (0.5 M NaCl) inhibited the expression of all genes for secreted proteins almost completely. Low temperature (20°C) did not affect the expression of the sll1891 gene of an unknown function and the slr0924 gene. The high temperature (44°C) suppressed the expression of all genes tested. A detailed study of the expression of the sll1694 (pilA1) gene, which encodes the main structural protein of cyanobacterial pili, pilin PilA1, demonstrated that virtually all stresses suppressed its expression. Thus, various stresses were shown to suppress the expression of most genes encoding Synechocystis secreted proteins.     

Effect of salt stress on genes encoding translation-associated proteins in Arabidopsis thaliana

Salinity negatively affects plant growth and disturbs chloroplast integrity. Here, we aimed at identifying salt-responsive translation-related genes in Arabidopsis thaliana with an emphasis on those encoding plastid-located proteins. We used quantitative real-time PCR to test the expression of 170 genes after short-term salt stress (up to 24 h) and identified several genes affected by the stress including: PRPL11, encoding plastid ribosomal protein L11, ATAB2, encoding a chloroplast-located RNA-binding protein presumably functioning as an activator of translation, and PDF1B, encoding a peptide deformylase involved in N-formyl group removal from nascent proteins synthesized in chloroplasts. These genes were previously shown to have important functions in chloroplast biology and may therefore represent new targets for biotechnological optimization of salinity tolerance.     

Analysis of Genes Expression of Spodoptera exigua Larvae upon AcMNPV Infection

Background

The impact of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) infection on host gene expression in Spodoptera exigua 4th instar larvae was investigated through the use of 454 sequencing-based RNA-seq of cDNA libraries developed from insects challenged with active AcMNPV or heat-inactivated AcMNPV.

Methodology/Principal Findings

By comparing the two cDNA libraries, we show that 201 host genes are significantly up-regulated and 234 genes are significantly down-regulated by active AcMNPV infection. Down-regulated host genes included genes encoding antimicrobial peptides, namely three gloverin isoforms and an attacin, indicating that the viral infection actively repressed the expression of a portion of the host immune gene repertoire. Another interesting group of down-regulated host genes included genes encoding two juvenile hormone binding proteins and a hexamerin, all of which are involved in juvenile hormone regulation. The expression of these genes was enhanced by the topical application of Juvenile Hormone III (JHIII) in the insects challenged with heat-inactivated AcMNPV. However, infection with the active virus strongly suppresses the expression of these three genes, regardless of the absence or presence of JHIII.

Conclusions/Significance

Using RNA-seq, we have identified groups of immune-regulated and juvenile hormone-regulated genes that are suppressed by infection with active AcMNPV. This information and further studies on the regulation of host gene expression by AcMNPV will provide the tools needed to enhance the utility of the virus as an effective protein expression system and as an insecticide.     

Salt Induces Expression of RH3.2A, Encoding an H3.2-type Histone H3 Protein in Rice (Oryza sativa L.)

Histone H3 is one of the four histones, along with H2A, H2B, and H4, which form the eukaryotic nucleosome octamer core. In this study, a new gene RH3.2A encoding an H3.2-type histone H3 protein from rice (Oryza sativa L.) was reported. RH3.2A was cloned through RT-PCR from salt-treated rice seedlings. This gene encoded a protein of 136 amino acid residues that were similar to some plant histone H3 proteins reported previously. However, the cDNA sequence of RH3.2A and other rice H3 genes were different. Alignment of RH3.2A encoding protein with other plant histone H3 proteins revealed that three amino acid residues (32, 88, and 91) were markedly different between H3.1-type and H3.2-type proteins. The mRNA expression analysis of RH3.2A revealed that RH3.2A gene was upregulated by salt stress in rice roots and ABA treatment in seedlings. The potential role of RH3.2A during salt stress was discussed.     

Identification of Genes Essential for Growth at High Salt Concentrations Using Salt-Sensitive Mutants of the Cyanobacterium Synechocystis sp. Strain PCC 6803

A collection of 17 salt-sensitive mutants of the cyanobacterium Synechocystis sp. strain PCC 6803 was obtained by random cartridge mutagenesis. The genes coding for proteins essential for growth at high salt concentrations were mapped on the completely known genome sequence of this strain. The two genes coding for enzymes involved in biosynthesis of the osmolyte glucosylglycerol were affected in nine mutants. Two mutants defective in a glycoprotease encoding gene gcp showed a reduced salt resistance. Four genes were identified not previously known to be essential for salt tolerance in cyanobacteria. These genes (slr1799, slr1087, sll1061, and sll1062) code for proteins not yet functionally characterized. Received: 21 May 2001 / Accepted: 27 June 2001     

Proteomic analysis of Synechocystis sp. PCC6803 responses to low-temperature and high light conditions

The global changes in protein expression of Synechocystis sp. PCC6803, a photosynthetic bacterium for the production of secondary metabolites as a green cell factory, were investigated by proteome separation and a subsequent tandem mass spectrometry. Two different proteome separation techniques, strong cation exchange chromatography and off-gel electrophoresis, were applied. The combination of the two proteome separation techniques enabled the comparative analysis of the differential regulation of the Synechocystis proteome in response to two different environmental factors, temperature and light. A total of 1,483 proteins were identified, which represent over 40% of the genes in Synechocystis. Our data showed that fatty acid metabolism was inhibited by (3R)-hydroxymyristol acyl carrier protein dehydrase (Sll1605) under low temperature conditions. The expression of UDP-N-acetylglucosamine acyltransferase (Sll0379) and 3-O-[3-hydroxymyristoyl] glucosamine N-acyltransferase (Slr0776), which is involved in lipopolysaccharide metabolism, was not observed under high light conditions. Under high light exposure, proteins related to iron-sulfur metabolism were detected, which may be responsible for maintaining the redox potential of the photosystem. High light under low temperature caused severe damage to the photosystem. Some of the responses to these stresses were similar to those previously reported for other photosynthetic organisms. Notably, this study revealed the followings: (i) low temperature inhibits fatty acid synthesis; (ii) high light inhibits lipopolysaccharides synthesis and stimulates the expression of iron-sulfur related proteins; and (iii) high light under low temperature induces the photorespiratory cycle. The global proteomic analysis clearly showed that stress conditions such as low temperature and/or high light induce cellular metabolisms related with the protection of their photosystems in the model microalga Synechocystis sp. PCC6803.