Transcriptomic changes triggered by carotenoid biosynthesis inhibitors and role of Citrus sinensis phosphate transporter 4;2 (CsPHT4;2) in enhancing carotenoid accumulation
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Carotenoid accumulation and chromoplast development in orange were perturbed by carotenoid inhibitors, and candidate genes were identified via transcriptomic analysis. The role of CsPHT4;2 in enhancing carotenoid accumulation was revealed.
Carotenoids are important plant pigments and their accumulation can be affected by biosynthesis inhibitors, but the genes involved were largely unknown. Here, application of norflurazon (NFZ), 2-(4-chlorophenylthio)-triethylamine hydrochloride (CPTA) and clomazone for 30 days to in vitro cultured sweet orange juice vesicles caused over-accumulation of phytoene (over 1000-fold), lycopene (2.92 μg g−1 FW, none in control), and deficiency in total carotenoids (reduced to 22%), respectively. Increased carotenoids were associated with bigger chromoplasts with enlarged plastoglobules or a differently crystalline structure in NFZ, and CPTA-treated juice vesicles, respectively. Global transcriptomic changes following inhibitor treatments were profiled. Induced expression of 1-deoxy-d-xylulose 5-phosphate synthase 1 by CPTA, hydroxymethylbutenyl 4-diphosphate reductase by both NFZ and CPTA, and reduced expression of chromoplast-specific lycopene β-cyclase by CPTA, as well as several downstream genes by at least one of the three inhibitors were observed. Expression of fibrillin 11 (CsFBN11) was induced following both NFZ and CPTA treatments. Using weighted correlation network analysis, a plastid-type phosphate transporter 4;2 (CsPHT4;2) was identified as closely correlated with high-lycopene accumulation induced by CPTA. Transient over-expression of CsPHT4;2 significantly enhanced carotenoid accumulation over tenfold in ‘Cara Cara’ sweet orange juice vesicle-derived callus. The study provides a valuable overview of the underlying mechanisms for altered carotenoid accumulation and chromoplast development following carotenoid inhibitor treatments and sheds light on the relationship between carotenoid accumulation and chromoplast development.
KeywordsChromoplast Fibrillin (FBN) Lycopene Orange Weighted correlation network analysis (WGCNA)
Chromoplast-specific carotenoid-associated protein
Chromoplast-specific lycopene β-cyclase
1-Deoxy-d-xylulose 5-phosphate synthase
Fragments per kilobase of transcript sequence per millions base pair
Kyoto encyclopedia of genes and genomes
Hydroxymethylbutenyl 4-diphosphate reductase
Plastid lipid-associated protein
Transmission electron microscopy
Weighted correlation network analysis
This work was supported by the National Key Research and Development Program of China (2016YFD0400100) and the 111 project (B17039).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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