The production of recombinant proteins is one of the most significant achievements of biotechnology in the last century. These proteins are produced in the eukaryotic or prokaryotic heterologous hosts. By increasing the omics data especially related to different heterologous hosts as well as the presence of new amenable genetic engineering tools, we can artificially engineer heterologous hosts to produce recombinant proteins in sufficient quantities. Numerous recombinant proteins have been produced and applied in various industries, and the global recombinant proteins market size is expected to be cast to reach USD 2.4 billion by 2027. Therefore, identifying the weakness and strengths of heterologous hosts is critical to optimize the large-scale biosynthesis of recombinant proteins. E. coli is one of the popular hosts to produce recombinant proteins. Scientists reported some bottlenecks in this host, and due to the increasing demand for the production of recombinant proteins, there is an urgent need to improve this host. In this review, we first provide general information about the E. coli host and compare it with other hosts. In the next step, we describe the factors involved in the expression of the recombinant proteins in E. coli . Successful expression of recombinant proteins in E. coli requires a complete elucidation of these factors. Here, the characteristics of each factor will be fully described, and this information can help to improve the heterologous expression of recombinant proteins in E. coli .

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MicroRNAs (miRNAs) are, small (roughly 19-25 nucleotides in length), conserved, non-coding, single-stranded, and functional RNA molecules with the properties of gene expression regulation through mRNA degradation, translation repression, mRNA deadenylation as well as gene silencing via histone methylation. They even have the ability to increase gene expression levels. The biogenesis of miRNAs is divided into two canonical and non-canonical pathways. The second pathway has a divergent mechanism for the biogenesis of miRNAs. miRNAs can be transcribed from specific genes or introns of protein-coding genes. A single miRNA species can control the expression of hundreds of genes, and also one gene can be the target of different miRNAs. These molecules have been identified in eukaryotic organisms such as mammals and plants and even in viruses. miRNAs play an inevitable role in the life cycle of eukaryotic cells. They are involved in any biological processes such as the regulation of cell proliferation and differentiation, apoptosis, signaling, and defense responses through their spatio-temporal expression manner. Aberrant expression of miRNAs is involved in a large number of biological disorders, which illustrates their great potential to be applied in the diagnosis and treatment of various diseases. miRNA inhibitors (anti-miRs) and artificial miRNAs (miRNA mimics) are two general approaches to balance the dysregulated miRNA levels that make it possible to treat various biological disorders. In this study, in general, the biogenesis and the role of miRNAs, the origin of miRNAs, viral miRNAs, miRNA detection procedures, in silico miRNA analysis tools, miRNA-based therapies and their obstacles, and miRNAs as potential non-invasive biomarkers are discussed. Finally, it is stated the importance of dietary miRNAs.

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Cauliflower Mosaic Virus (CaMV) is a plant Pararetrovirus with a double-stranded DNA genome distributed worldwide. This study analyzed migration, evolution, and synonymous codon pattern of CaMV and the factors that shape it. We extracted genomic sequences of 121 isolates of CaMV, which were reported from various regions-hosts, from the NCBI database. The evolution of viruses has been widely studied by analyzing their nucleotides and coding regions/codons using different methods. Analysis of the CaMV phylogenetic tree shows that it divides most of the sequences into two main groups: Group I includes Irananin, Japanese, and American-European subgroups, and Group II includes Grecian, Turkish, and Iranian subgroups. Analysis of effective codon count, and relative codon deoptimization index, showed that natural selection is a major driving force in CaMV. Furthermore, Relative synonymous codon usage (RSCU) and neutrality analyses show that CaMV prefers A-ending codons and that one codon, namely GGA, was overrepresented. Analysis of dinucleotide composition demonstrates that nucleotide A was the most abundant in the CaMV coding sequences, and that the most frequent nucleotide at the third position of the codon was A3S. In CaMV, host adaptation was highest for Brassica oleracea and lowest for Raphanus sativus. Therefore the CaMV codon pattern is mostly shaped by the need to escape antiviral responses associated with host dinucleotides and translational efficiency. These values indicate that the study provides useful information on the codon usage analysis of CaMV and can be used to understand host adaptation to the virus environment and its evolution. This is the first study on codon usage bias of CaMV in the world.