Identification, Characterization, and Expression Analysis of Carotenoid Biosynthesis Genes and Carotenoid Accumulation in Watercress (Nasturtium officinale R. Br.)

Metabolic Profiling of Primary and Secondary Metabolites in Kohlrabi (Brassica oleracea var. gongylodes) Sprouts Exposed to Different Light-Emitting Diodes

Light-emitting diode (LED) technology is one of the most important light sources in the plant industry for enhancing growth and specific metabolites in plants. In this study, we analyzed the growth, primary and secondary metabolites of 10 days old kohlrabi (Brassica oleracea var. gongylodes) sprouts exposed to different LED light conditions. The results showed that the highest fresh weight was achieved under red LED light, whereas the highest shoot and root lengths were recorded below the blue LED light. Furthermore, high-performance liquid chromatography (HPLC) analysis revealed the presence of 13 phenylpropanoid compounds, 8 glucosinolates (GSLs), and 5 different carotenoids. The phenylpropanoid and GSL contents were highest under blue LED light. In contrast, the carotenoid content was found to be maximum beneath white LED light. Principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) of the 71 identified metabolites using HPLC and gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) showed a clear separation, indicating that different LEDs exhibited variation in the accumulation of primary and secondary metabolites. A heat map and hierarchical clustering analysis revealed that blue LED light accumulated the highest amount of primary and secondary metabolites. Overall, our results demonstrate that exposure of kohlrabi sprouts to blue LED light is the most suitable condition for the highest growth and is effective in increasing the phenylpropanoid and GSL content, whereas white light might be used to enhance carotenoid compounds in kohlrabi sprouts.

Comparative Genomic Analysis of Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05 for Producing Macular Pigment

Sphingomonas morindae sp. NBD5, which we previously identified and tested, is a new bacterial strain for producing lutein. Here, based on the next-generation sequencing technology, we analyzed high throughput genomic sequences and compared related functional genes of Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05. The genome of Sphingomonas morindae sp. NBD5 has two sets of chromosomes, which is 4,239,716 bp and harbors 3882 protein coding genes. There are 59 protein-coding genes related to the macular pigment (MP) biosynthesis, of which four genes (ackA, pgm, gpmI and pckA) are unique. These genes, pckG, porB, meh, and fldA, are unique in Sphingopyxis sp. USTB-05. The analysis of Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05 genomes gives an insight into the new pathway for MP production. These genes for the transformation of glucose to MP were also found in Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05. This study expands the understanding of the pathway for complete biosynthesis of MP by Sphingomonas morindae sp. NBD5 and Sphingopyxis sp. USTB-05.

Identification, In Silico Characterization, and Differential Expression Profiles of Carotenoid, Xanthophyll, Apocarotenoid Biosynthetic Pathways Genes, and Analysis of Carotenoid and Xanthophyll Accumulation in Heracleum moellendorffii Hance

Heracleum moellendorffii Hance is a non-woody forest plant widely used in China, Korea, and Japan because of its various therapeutic properties. However, the genetic details of the carotenoid pathway (CP), xanthophyll pathway (XP), and apocarotenoid pathway (AP) genes have not been studied. Thus, the CP, XP, and AP genes of H. moellendorffii were detected and analyzed. A total of fifteen genes were identified, of which eight, four, and three belonged to CP, XP, and AP, respectively. All identified genes possessed full open reading frames. Phylogenetic characterization of the identified gene sequences showed the highest similarity with other higher plants. Multiple alignments and 3D dimensional structures showed several diverse conserved motifs, such as the carotene-binding motif, dinucleotide-binding motif, and aspartate or glutamate residues. The results of real-time PCR showed that the CP, XP, and AP genes were highly expressed in leaves, followed by the stems and roots. In total, eight different individual carotenoids were identified using HPLC analysis. The highest individual and total carotenoid content were achieved in the leaves, followed by the stems and roots. This study will provide more information on the gene structure of the CP, XP, and AP genes, which may help to increase the accumulation of carotenoids in H. moellendorffii through genetic engineering. These results could be helpful for further molecular and functional studies of CP, XP, and AP genes.