Structure of Pigment Metabolic Pathways and Their Contributions to White Tepal Color Formation of Chinese Narcissus tazetta var. chinensis cv Jinzhanyintai

Abstract

Chinese narcissus (Narcissus tazetta var. chinensis) is one of the ten traditional flowers in China and a famous bulb flower in the world flower market. However, only white color tepals are formed in mature flowers of the cultivated varieties, which constrains their applicable occasions. Unfortunately, for lack of genome information of narcissus species, the explanation of tepal color formation of Chinese narcissus is still not clear. Concerning no genome information, the application of transcriptome profile to dissect biological phenomena in plants was reported to be effective. As known, pigments are metabolites of related metabolic pathways, which dominantly decide flower color. In this study, transcriptome profile and pigment metabolite analysis methods were used in the most widely cultivated Chinese narcissus “Jinzhanyintai” to discover the structure of pigment metabolic pathways and their contributions to white tepal color formation during flower development and pigmentation processes. By using comparative KEGG pathway enrichment analysis, three pathways related to flavonoid, carotenoid and chlorophyll pigment metabolism showed significant variations. The structure of flavonoids metabolic pathway was depicted, but, due to the lack of F3ʹ5ʹH gene; the decreased expression of C4H, CHS and ANS genes; and the high expression of FLS gene, the effect of this pathway to synthesize functional anthocyanins in tepals was weak. Similarly, the expression of DXS, MCT and PSY genes in carotenoids synthesis sub-pathway was decreased, while CCD1/CCD4 genes in carotenoids degradation sub-pathway was increased; therefore, the effect of carotenoids metabolic pathway to synthesize adequate color pigments in tepals is restricted. Interestingly, genes in chlorophyll synthesis sub-pathway displayed uniform down-regulated expression, while genes in heme formation and chlorophyll breakdown sub-pathways displayed up-regulated expression, which also indicates negative regulation of chlorophyll formation. Further, content change trends of various color metabolites detected by HPLC in tepals are consistent with the additive gene expression patterns in each pathway. Therefore, all three pathways exhibit negative control of color pigments synthesis in tepals, finally resulting in the formation of white tepals. Interestingly, the content of chlorophyll was more than 10-fold higher than flavonoids and carotenoids metabolites, which indicates that chlorophyll metabolic pathway may play the major role in deciding tepal color formation of Chinese narcissus.

Transcriptome profiling of two contrasting ornamental cabbage (Brassica oleracea var. acephala) lines provides insights into purple and white inner leaf pigmentation

“…The unigenes related to chlorophyll biosynthesis ( HEMA1 , BONG005190.1G; CRD1 , Bol004197G; PORC1 , Bol040837G; PORC2 , Bol011626G) and the chlorophyll cycle ( CAO , Bol033406G) were up-regulated in mid-age (S2) and older (S3) leaves in both the ornamental cabbage lines (Fig. 8 ), similar to what has been reported by Ren et al [ 44 ] for Chinese narcissus. On the other hand, CLH1 (Bol026880G), a gene involved in chlorophyll degradation, showed an opposite expression pattern except in the older leaf (sample F, S3) of white ornamental cabbage.…”

Comparative Proteomic Analysis of Coregulation of CIPK14 and WHIRLY1/3 Mediated Pale Yellowing of Leaves in Arabidopsis

“…Pigments were extracted after incubating for 48 h in the dark. The absorbance of the extracts was measured at 470, 649, and 665 nm by the Flexstation 3 Microplate Reader (Molecular Devices, Silicon Valley, CA, USA), and the total chlorophyll content was determined according the method described in [ 60 ].…”

Exploring the Molecular Mechanism of Blue Flower Color Formation in Hydrangea macrophylla cv. “Forever Summer”

“…Carotenoids are also the basis for the formation of flower coloration in many plants, mainly underlying yellow, orange, and red coloration. The flower color of plants, such as Chinese narcissus ( Ren et al, 2017 ) and Camellia ( Zhou et al, 2017 ), is mainly affected by carotenoids, and its regulatory mechanism has also been well elucidated. During the formation of infertile flowers, almost all DEGs in the carotenoid biosynthetic pathway, including PSY, CRTZ, ZEP , and VED , were up-regulated at FSF1 and FSF2, and the high expression of these genes likely increased carotenoid content.…”