Transcriptome Sequencing and Biochemical Analysis of Perianths and Coronas Reveal Flower Color Formation in <i>Narcissus pseudonarcissus</i>

• Main Authors: Xi Li, Dongqin Tang, Hui Du, Yimin Shi
• Format: Article
• Language: English
• Published: MDPI AG 2018-12-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>Narcissus pseudonarcissus</i>; transcriptome; biochemical analysis; carotenoids; CCD4
• Online Access: https://www.mdpi.com/1422-0067/19/12/4006

<i>Narcissus pseudonarcissus</i> is an important bulbous plant with white or yellow perianths and light yellow to orange-red coronas, but little is known regarding the biochemical and molecular basis related to flower color polymorphisms. To investigate the mechanism of color formation, RNA-Seq of flower of two widely cultured cultivars (&#8216;Slim Whitman&#8217; and &#8216;Pinza&#8217;) with different flower color was performed. A total of 84,463 unigenes were generated from the perianths and coronas. By parallel metabolomic and transcriptomic analyses, we provide an overview of carotenoid biosynthesis, degradation, and accumulation in <i>N. pseudonarcissus</i>. The results showed that the content of carotenoids in the corona was higher than that in the perianth in both cultivars. Accordingly, phytoene synthase (PSY) transcripts have a higher abundance in the coronas than that in perianths. While the expression levels of carotenoid biosynthetic genes, like <i>GGPPS</i>, <i>PSY</i>, and <i>LCY-e</i>, were not significantly different between two cultivars. In contrast, the carotenoid degradation gene <i>NpCCD4</i> was highly expressed in white-perianth cultivars, but was hardly detected in yellow-perianth cultivars. Silencing of <i>NpCCD4</i> resulted in a significant increase in carotenoid accumulation, especially in all-<i>trans</i>-&#946;-carotene. Therefore, we presume that <i>NpCCD4</i> is a crucial factor that causes the low carotenoid content and color fading phenomenon of &#8216;Slim Whitman&#8217; by mediating carotenoid turnover. Our findings provide mass RNA-seq data and new insights into carotenoid metabolism in <i>N. pseudonarcissus</i>.