Comparative transcriptomic and metabolomic analyses of carotenoid biosynthesis reveal the basis of white petal color in Brassica napus

Abstract

Main conclusion The molecular mechanism underlying white petal color in Brassica napus was revealed by transcriptomic and metabolomic analyses. Abstract Rapeseed (Brassica napus L.) is one of the most important oilseed crops worldwide, but the mechanisms underlying flower color in this crop are known less. Here, we performed metabolomic and transcriptomic analyses of the yellow-flowered rapeseed cultivar ‘Zhongshuang 11’ (ZS11) and the white-flowered inbred line ‘White Petal’ (WP). The total carotenoid contents were 1.778-fold and 1.969-fold higher in ZS11 vs. WP petals at stages S2 and S4, respectively. Our findings suggest that white petal color in WP flowers is primarily due to decreased lutein and zeaxanthin contents. Transcriptome analysis revealed 10,116 differentially expressed genes with a fourfold or greater change in expression (P-value less than 0.001) in WP vs. ZS11 petals, including 1,209 genes that were differentially expressed at four different stages and 20 genes in the carotenoid metabolism pathway. BnNCED4b, encoding a protein involved in carotenoid degradation, was expressed at abnormally high levels in WP petals, suggesting it might play a key role in white petal formation. The results of qRT-PCR were consistent with the transcriptome data. The results of this study provide important insights into the molecular mechanisms of the carotenoid metabolic pathway in rapeseed petals, and the candidate genes identified in this study provide a resource for the creation of new B. napus germplasms with different petal colors.

Transcriptome Analysis Reveals Key Genes and Pathways Associated with the Petal Color Formation in Cabbage (Brassica oleracea L. var. capitata)

“…Among these five DEGs, BoNCED4.2 ( BoCCD4 ) and BoAAO3 were significantly up-regulated in both the A192-1 and YF-2 petals. The BoCCD4 gene responsible for petal color formation was barely expressed in the yellow petals, which is consistent with the findings of previous studies [ 8 , 11 , 14 ]. We speculated that the cabbage petals will show varying degrees of color change from yellow to white with the change in the BoCCD4 expression level.…”

“…In Brassica rapa , the carotenoid biosynthesis-related genes and the paralogues of each carotenoid biosynthesis-related gene showed different expression patterns across flower, stem, leaf, root and silique tissues according to transcriptome analysis [ 7 ]. In Brassica napus , the transcriptome analysis of white and yellow petals revealed 20 significantly differentially expressed genes (DEGs) involved in the carotenoid metabolic pathway, among which BnNCED4b was markedly up-regulated in white petals [ 8 ]. In papaya, transcriptome analysis showed that the expression levels of key carotenoid biosynthesis pathway-related genes were different between yellow peel and red flesh tissues [ 3 ].…”

“…In B. napus and Chinese kale, the insertion of a CACTA-like transposable element disrupts the function of BnaC3.CCD4 and BoCCD4.2 , causing the petal color to change from white to yellow [ 5 , 11 ]. In Osmanthus fragrans and B. napus , the expression of OfCCD4 and BnNCED4b can be regulated by the transcription factors OfWRKY3 and BnWRKY22 , associated with the white petal formation, respectively [ 8 , 12 ]. In Mimulus lewisii , the loss-of-function of TF R2R3-MYB leads to the down-regulation of all carotenoid biosynthetic genes and to reduced carotenoid content in flowers [ 13 ].…”

Multi-omics Analyses Provide Insight into the Biosynthesis Pathways of Fucoxanthin in Isochrysis galbana

“…Studies have showed that multiple key genes are related to the Fx synthesis pathway, including PYS, PDS, ZISO, ZDS, CRTISO, and LCYb [10][11]14]. Comprehensive analysis of multi-omics helps reveal the underlying accumulation of carotenoid [26][27][28][29]. For example, Jia et al revealed the molecular mechanism of white petal color in Brassica napus by metabolomic and transcriptomic analyses, mining several candidate genes involved in carotenoid biosynthesis (BnWRKY22, BnNCED4b) [27].…”

“…Comprehensive analysis of multi-omics helps reveal the underlying accumulation of carotenoid [26][27][28][29]. For example, Jia et al revealed the molecular mechanism of white petal color in Brassica napus by metabolomic and transcriptomic analyses, mining several candidate genes involved in carotenoid biosynthesis (BnWRKY22, BnNCED4b) [27]. Xia et al found that DEGs and DACs involved in carotenoid biosynthesis were significantly up-regulated and accumulated more in yellow flower petals than in the green bud petals and white flower petals, indicating a predominantly promotion function for color transition in Lonicera japonica [29].…”