Molecular Mechanism Involved in Carotenoid Metabolism in Post-Smolt Atlantic Salmon: Astaxanthin Metabolism During Flesh Pigmentation and Its Antioxidant Properties

Pummelo (Citrus maxima) is one of important fruit trees, which belongs to Citrus species. The fruits of different pummelo cultivars have different colors and differ in the contents of carotenoid. Our results clearly showed that ‘Huangjinmiyou’ (HJMY) has the highest content of β-carotene, followed by ‘Hongroumiyou’ (HRMY) and ‘Guanximiyou’ (GXMY). Lycopene is dominantly accumulated in HRMY. However, the molecular mechanism underlying the carotenoid accumulation in pummelo flesh is not fully understood. In this study, we used the RNA-Seq technique to investigate the candidate genes of carotenoid metabolism in the flesh of pummelo cv. GXMY and its mutants HRMY and HJMY in three development periods of fruit. After data assembly and bioinformatic analysis, a total of 357 genes involved in biosynthesis of secondary metabolites were isolated, of which 12 differentially expressed genes (DEGs) are involved in carotenoid biosynthesis. Among these 12 DEGs, phytoene synthase (PSY2), lycopene β-cyclase (LYCB2), lycopene Ɛ-cyclase (LYCE), carotenoid cleavage dioxygenases (CCD4), 9-cis-epoxycarotenoid dioxygenase (NCED2), aldehyde oxidase 3 (AAO3), and ABA 8′-hydroxylases (CYP707A1) are the most distinct DEGs in three pummelo cultivars. The co-expression analysis revealed that the expression patterns of several transcription factors such as bHLH, MYB, ERF, NAC and WRKY are highly correlated with DEGs, which are involved in carotenoid biosynthesis. In addition, the expression patterns of 22 DEGs were validated by real-time quantitative PCR (RT-qPCR) and the results are highly concordant with the RNA-Seq results. Our results provide a global vision of transcriptomic profile among three pummelo cultivars with different pulp colors. These results would be beneficial to further study the molecular mechanism of carotenoid accumulation in pummelo flesh and help the breeding of citrus with high carotenoid content.

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The genes crucial to carotenoid metabolism under elevated CO2 levels in carrot (Daucus carota L.)

Scientific Reports ◽

10.1038/s41598-021-91522-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hongxia Song ◽

Qiang Lu ◽

Leiping Hou ◽

Meilan Li

Keyword(s):

Molecular Mechanism ◽

Daucus Carota ◽

Carotenoid Biosynthesis ◽

Practical Significance ◽

Carotenoid Content ◽

Rna Seq ◽

Daucus Carota L ◽

Carotenoid Metabolism ◽

Biological Yield ◽

Missed Opportunity

AbstractThe CO2 saturation point can reach as high as 1819 μmol· mol−1 in carrot (Daucus carota L.). In recent years, carrot has been cultivated in out-of-season greenhouses, but the molecular mechanism of CO2 enrichment has been ignored, and this is a missed opportunity to gain a comprehensive understanding of this important process. In this study, it was found that CO2 enrichment increased the aboveground and belowground biomasses and greatly increased the carotenoid contents. Twenty genes related to carotenoids were discovered in 482 differentially expressed genes (DEGs) through RNA sequencing (RNA-Seq.). These genes were involved in either carotenoid biosynthesis or the composition of the photosystem membrane proteins, most of which were upregulated. We suspected that these genes were directly related to quality improvement and increases in biomass under CO2 enrichment in carrot. As such, β-carotene hydroxylase activity in carotenoid metabolism and the expression levels of coded genes were determined and analysed, and the results were consistent with the observed change in carotenoid content. These results illustrate the molecular mechanism by which the increase in carotenoid content after CO2 enrichment leads to the improvement of quality and biological yield. Our findings have important theoretical and practical significance.

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