Gene expression profile during seed development of Bixa orellana accessions varying in bixin pigment.

Diverse morphological, cellular and physiological changes occur during seed maturation in Bixa orellana when the seed tissues form specialized cell glands that produce reddish latex with high bixin amounts. Transcriptomic profiling during seed development in three B. orellana accessions (P12, N4 and N5) with contrasting morphologic characteristics showed enrichment in pathways of triterpenes, sesquiterpenes, and cuticular wax biosynthesis. WGCNA allows groups of all identified genes in six modules the module turquoise, the largest and highly correlated with the bixin content. The high number of genes in this module suggests a diversification of regulatory mechanisms for bixin accumulation with the genes belonging to isoprene, triterpenes and carotene pathways, being more highly correlated with the bixin content. Analysis of key genes of the mevalonate (MVA) and the 2C-methyl-D-erythritol-4-phosphate (MEP) pathways revealed specific activities of orthologs of BoHMGR, BoFFP, BoDXS, and BoHDR. This suggests that isoprenoid production is necessary for compounds included in the reddish latex of developing seeds. The carotenoid-related genes BoPSY2, BoPDS1 and BoZDS displayed a high correlation with bixin production, consistent with the requirement for carotene precursors for apocarotenoid biosynthesis. The BoCCD gene member (BoCCD4-4) and some BoALDH (ALDH2B7.2 and ALDH3I1) and BoMET (BoSABATH1 and BoSABATH8) gene members were highly correlated to bixin in the final seed development stage. This suggested a contributing role for several genes in apocarotenoid production. The results revealed high genetic complexity in the biosynthesis of reddish latex and bixin in specialized seed cell glands in different accessions of B. orellana suggesting gene expression coordination between both metabolite biosynthesis processes.

Comparative genomics of DNA-binding transcription factors in archaeal and bacterial organisms.

Archaea represent a diverse phylogenetic group that includes free-living, extremophile, mesophile, symbiont, and opportunistic organisms. These prokaryotic organisms share a high significant similarity with the basal transcriptional machinery of Eukarya, and they share regulatory mechanisms with Bacteria, such as operonic organization and DNA-binding transcription factors (TFs). In this work, we identified the repertoire of TFs in 415 archaeal genomes and compared them with their counterparts in bacterial genomes. The comparisons of TFs, at a global level and per family, allowed us to identify similarities and differences between the repertoires of regulatory proteins of bacteria and archaea. For example, 11 of 62 families are more highly abundant in archaea than bacteria, and 13 families are abundant in bacteria but not in archaea and 38 families have similar abundances in the two groups. In addition, we found that archaeal TFs have a lower isoelectric point than bacterial proteins, i.e., they contain more acidic amino acids, and are smaller than bacterial TFs. Our findings suggest a divergence occurred for the regulatory proteins, even though they are common to archaea and bacteria. We consider that this analysis contributes to the comprehension of the structure and functionality of regulatory proteins of archaeal organisms.

Identification of functional signatures in the metabolism of the three cellular domains of life.

In order to identify common and specific enzymatic activities associated with the metabolism of the three cellular domains of life, the conservation and variations between the enzyme contents of Bacteria, Archaea, and Eukarya organisms were evaluated. To this end, the content of enzymes belonging to a particular pathway and their abundance and distribution in 1507 organisms that have been annotated and deposited in the KEGG database were assessed. In addition, we evaluated the consecutive enzymatic reaction pairs obtained from metabolic pathway reactions and transformed into sequences of enzymatic reactions, with catalytic activities encoded in the Enzyme Commission numbers, which are linked by a substrate. Both analyses are complementary: the first considers individual reactions associated with each organism and metabolic map, and the second evaluates the functional associations between pairs of consecutive reactions. From these comparisons, we found a set of five enzymatic reactions that were widely distributed in all the organisms and considered here as universal to Bacteria, Archaea, and Eukarya; whereas 132 pairs out of 3151 reactions were identified as significant, only 5 of them were found to be widely distributed in all the taxonomic divisions. However, these universal reactions are not widely distributed along the metabolic maps, suggesting their dispensability to all metabolic processes. Finally, we found that universal reactions are also associated with ancestral domains, such as those related to phosphorus-containing groups with a phosphate group as acceptor or those related to the ribulose-phosphate binding barrel, triosephosphate isomerase, and D-ribose-5-phosphate isomerase (RpiA) lid domain, among others. Therefore, we consider that this analysis provides clues about the functional constraints associated with the repertoire of enzymatic functions per organism.