Multi-Omics Driven Assembly and Annotation of the Sandalwood (Santalum album) Genome.

Indian sandalwood (Santalum album) is an important tropical evergreen tree known for its fragrant heartwood-derived essential oil and its valuable carving wood. Here, we applied an integrated genomic, transcriptomic, and proteomic approach to assemble and annotate the Indian sandalwood genome. Our genome sequencing resulted in the establishment of a draft map of the smallest genome for any woody tree species to date (221 Mb). The genome annotation predicted 38,119 protein-coding genes and 27.42% repetitive DNA elements. In-depth proteome analysis revealed the identities of 72,325 unique peptides, which confirmed 10,076 of the predicted genes. The addition of transcriptomic and proteogenomic approaches resulted in the identification of 53 novel proteins and 34 gene-correction events that were missed by genomic approaches. Proteogenomic analysis also helped in reassigning 1,348 potential noncoding RNAs as bona fide protein-coding messenger RNAs. Gene expression patterns at the RNA and protein levels indicated that peptide sequencing was useful in capturing proteins encoded by nuclear and organellar genomes alike. Mass spectrometry-based proteomic evidence provided an unbiased approach toward the identification of proteins encoded by organellar genomes. Such proteins are often missed in transcriptome data sets due to the enrichment of only messenger RNAs that contain poly(A) tails. Overall, the use of integrated omic approaches enhanced the quality of the assembly and annotation of this nonmodel plant genome. The availability of genomic, transcriptomic, and proteomic data will enhance genomics-assisted breeding, germplasm characterization, and conservation of sandalwood trees.

Quantitative Proteomic and Phosphoproteomic Analysis of H37Ra and H37Rv Strains of Mycobacterium tuberculosis.

Mycobacterium tuberculosis, the causative agent of tuberculosis, accounts for 1.5 million human deaths annually worldwide. Despite efforts to eradicate tuberculosis, it still remains a deadly disease. The two best characterized strains of M. tuberculosis, virulent H37Rv and avirulent H37Ra, provide a unique platform to investigate biochemical and signaling pathways associated with pathogenicity. To delineate the biomolecular dynamics that may account for pathogenicity and attenuation of virulence in M. tuberculosis, we compared the proteome and phosphoproteome profiles of H37Rv and H37Ra strains. Quantitative phosphoproteomic analysis was performed using high-resolution Fourier transform mass spectrometry. Analysis of exponential and stationary phases of these strains resulted in identification and quantitation of 2709 proteins along with 512 phosphorylation sites derived from 257 proteins. In addition to confirming the presence of previously described M. tuberculosis phosphorylated proteins, we identified 265 novel phosphorylation sites. Quantitative proteomic analysis revealed more than five-fold upregulation of proteins belonging to virulence associated type VII bacterial secretion system in H37Rv when compared to those in H37Ra. We also identified 84 proteins, which exhibited changes in phosphorylation levels between the virulent and avirulent strains. Bioinformatics analysis of the proteins altered in their level of expression or phosphorylation revealed enrichment of pathways involved in fatty acid biosynthesis and two-component regulatory system. Our data provides a resource for further exploration of functional differences at molecular level between H37Rv and H37Ra, which will ultimately explain the molecular underpinnings that determine virulence in tuberculosis.

Identification and characterization of proteins encoded by chromosome 12 as part of chromosome-centric human proteome project.

Chromosome-centric human proteome project (C-HPP) is a global initiative to comprehensively characterize proteins encoded by genes across all human chromosomes by teams focusing on individual chromosomes. Here, we report mass spectrometry-based identification and characterization of proteins encoded by genes on chromosome 12. Our study is based on proteomic profiling of 30 different histologically normal human tissues and cell types using high-resolution mass spectrometry. In our analysis, we identified 1,535 proteins encoded by 836 genes on human chromosome 12. This includes 89 genes that are designated as "missing proteins" by "neXtProt" as they did not have any prior evidence either by mass spectrometry or by antibody-based detection methods. We identified several variant peptides that reflected coding SNPs annotated in dbSNP database. We also confirmed the start sites of ∼200 proteins by identifying protein N-terminal acetylated peptides. We also identified alternative start sites for 11 proteins that were not annotated in public databases until now. Most importantly, we identified 12 novel protein coding regions on chromosome 12 using our proteogenomics strategy. All of the 12 regions have been annotated as pseudogenes in public databases. This study demonstrates that there is scope for significantly improving annotation of protein coding genes in the human genome using mass-spectrometry-derived data. Individual efforts as part of C-HPP initiative should significantly contribute toward enriching human protein annotation. The data have been deposited to ProteomeXchange with identifier PXD000561.