Synonymous codon usage of 53 protein coding genes in chloroplast genome of Coffea arabica was analyzed for the first time to find out the possible factors contributing codon bias. All preferred synonymous codons were found to use A/T ending codons as chloroplast genomes are rich in AT. No difference in preference for preferred codons was observed in any of the two strands, viz., leading and lagging strands. Complex correlations between total base compositions (A, T, G, C, GC) and silent base contents (A3, T3, G3, C3, GC3) revealed that compositional constraints played crucial role in shaping the codon usage pattern of C. arabica chloroplast genome. ENC Vs GC3 plot grouped majority of the analyzed genes on or just below the left side of the expected GC3 curve indicating the influence of base compositional constraints in regulating codon usage. But some of the genes lie distantly below the continuous curve confirmed the influence of some other factors on the codon usage across those genes. Influence of compositional constraints was further confirmed by correspondence analysis as axis 1 and 3 had significant correlations with silent base contents. Correlation of ENC with axis 1, 4 and CAI with 1, 2 prognosticated the minor influence of selection in nature but exact separation of highly and lowly expressed genes could not be seen. From the present study, we concluded that mutational pressure combined with weak selection influenced the pattern of synonymous codon usage across the genes in the chloroplast genomes of C. arabica.

BackgroundComparative study of synonymous codon usage variations and factors influencing its diversification in α - cyanobacterial descendant Paulinella chromatophora and β - cyanobacterium Synechococcus elongatus PCC6301 has not been reported so far. In the present study, we investigated various factors associated with synonymous codon usage in the genomes of P. chromatophora and S. elongatus PCC6301 and findings were discussed.ResultsMutational pressure was identified as the major force behind codon usage variation in both genomes. However, correspondence analysis revealed that intensity of mutational pressure was higher in S. elongatus than in P. chromatophora. Living habitats were also found to determine synonymous codon usage variations across the genomes of P. chromatophora and S. elongatus.ConclusionsWhole genome sequencing of α-cyanobacteria in the cyanobium clade would certainly facilitate the understanding of synonymous codon usage patterns and factors contributing its diversification in presumed ancestors of photosynthetic endosymbionts of P. chromatophora.

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Background Finger millet is the most important food grain in the world for its nutritional benefits. Finger millet is genetically and geographically diverse and widely spread in the African and Asian sub-continent. Therefore, the present study was undertaken to analyze the genetic diversity using ISSR genetic markers using 15 ISSR primers. Results About 23 genotypes of widely cultivated finger millet cultivars of economically important ones were characterized and the ISSR markers were critically analyzed for their performance with parameters such as polymorphic information content (PIC), effective multiplex ratio (EMR), marker index (MI), and resolving power (RP). In this study, 175 loci were scored across the 23 cultivars of finger millet, and out of these 173 loci (98%) were polymorphic, revealing the suitability of these loci for genetic diversity analysis with ISSR marker. The average number of polymorphic loci per primer was 11.50 with varying sizes from 100 bp to 2500 bp. ISSR primers that showed higher polymorphism were found to have higher EMR and MI values up to 15.30 and 13.44, respectively. Conclusion High degree of polymorphism supported with distinct differences of all the marker parameters revealed the suitability of ISSR markers for determining the genotypic differences based on ISSR markers among the 23 genotypes of finger millet. The possible application of the ISSR marker in the conservation and management of finger millet genetic resources is discussed.

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