We explored the relationship between skin color and the expression of genes related to carotenoid biosynthesis during fruit ripening in two citrus cultivars, ‘Shiranuhi’ (a hybrid mandarin cultivar) and ‘Suneat’ (mutant cultivar derived from a natural bud mutation of ‘Shiranuhi’). We identified 16 and 7 genes putatively involved in carotenoid biosynthesis and regulation via phylogenetic analysis in sweet orange. Further, we determined the expression pattern of these genes by quantitative real time reverse transcriptase PCR (qRT-PCR). The result showed that the expression levels of CsPSY (Cs6g15910), CsZDS (Cs3g11180), CsZ-ISO (Cs5g24730), CsBCH1 (Cs9g19270), CsFUL2 (Cs5g12280), CsTAGL1 (Cs7g16960), CsRIN1 (Cs6g19680), CsRIN2 (Cs7g10980), and CsHY5 (Cs7g05140) were up-regulated in the skin of mutant cultivar ‘Suneat’ than any other tissues of both citrus cultivars. Of these CsPSY , CsZDS , CsZ-ISO and CsBCH1 genes were related to carotenoid biosynthesis and CsFUL2 , CsTAGL1 , CsRIN1 , CsRIN2 , and CsHY5 were known to involve in the regulation of carotenoid biosynthesis. Our results reveal that the attractive dark orange skin color of ‘Suneat’ might be due to the up-regulation of carotenoid biosynthetic as well as regulatory genes and thereby higher levels carotenoids at ripening.

中文翻译：

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新型暗皮柑橘突变品种“Suneat”中类胡萝卜素生物合成相关基因的鉴定和表征

我们探讨了两种柑橘品种'Shiranuhi'（杂交柑橘品种）和'Suneat'（源自'Shiranuhi'天然芽突变的突变品种）果实成熟过程中皮肤颜色与类胡萝卜素生物合成相关基因表达之间的关系）。我们通过甜橙中的系统发育分析确定了 16 和 7 个可能参与类胡萝卜素生物合成和调控的基因。此外，我们通过定量实时逆转录酶 PCR (qRT-PCR) 确定了这些基因的表达模式。结果表明，CsPSY(Cs6g15910)、CsZDS(Cs3g11180)、CsZ-ISO(Cs5g24730)、CsBCH1(Cs9g19270)、CsFUL2(Cs5g12280)、Cs70g)、10CsTAGL6(CsTAGL6)、10CsTAGL16C10G10C10G10CsG16C100 和 CsHY5 (Cs7g05140) 在突变品种“Suneat”的表皮中比两种柑橘品种的任何其他组织上调。在这些 CsPSY 中，CsZDS、CsZ-ISO 和 CsBCH1 基因与类胡萝卜素生物合成有关，已知 CsFUL2、CsTAGL1、CsRIN1、CsRIN2 和 CsHY5 参与类胡萝卜素生物合成的调节。我们的研究结果表明，'Suneat' 诱人的深橙色皮肤颜色可能是由于类胡萝卜素生物合成和调控基因的上调，从而导致成熟时类胡萝卜素水平较高。