Project description:The complete genome sequence of Narcissus yellow stripe potyvirus (NYSV) isolated from Narcissus tazetta cv. Paperwhite exhibiting leaf chlorotic stripe symptoms was determined for the first time from India. The viral genome sequence contained 9650 nucleotides that encode a large polyprotein (372.36 kDa) of 3103 amino acids. The comparison of the NYSV genome sequences with corresponding sequences of other potyviruses revealed 90-97% identities and closest phylogenetic relationships with NYSV-Zhangzhou-1 and -ZZ-2 isolates infecting N. tazetta reported from China. Therefore, the NYSV isolate understudy was considered as a new member of NYSV and designated as NYSV-NAR2.
Project description:Narcissus tazetta L. is a bulbous ornamental plant popular for its notable fragrant flowers which make it the plant of high importance. In spite of its economic value, narcissus is found to be susceptible for a number of diseases borne by fungi, bacteria, nematodes, and viruses. A potyvirus, Cyrtanthus elatus virus-A isolate NBRI16 (CEVA-NBRI16), associated with leaf chlorotic stripe disease of N. tazetta cv. Paperwhite was reported for first time in India from our laboratory based on the partial coat protein gene sequence. In present study, the full-length genomic sequence of CEVA-NBRI16 is determined which consists of 9942 nucleotides, excluding the polyA tail, and encodes a single large polyprotein of 3102 amino acids with the genomic features typical of a potyvirus. It shares highest 93% nucleotide sequence identity and closest phylogenetic relationship with sequences of CEVA-Marijiniup7-1 and CEVA-Marijiniup7-2, both reported from Australia on Cyrtanthus elatus host. The full-length genomic sequence of CEVA from narcissus plant is being reported for the first time from India.
Project description:In Narcissus tazetta, a monocotyledonous bulbous geophyte, floral initiation and differentiation occur within the bulb during the quiescent period in summer, when ambient temperatures are relatively high and the bulb is located underground with no foliage or roots. In many plant species, FLOWERING LOCUS T (FT) and its homologues are considered powerful promoters of flowering. The Narcissus FT gene homologue (NtFT) was isolated, and organ-specific expression patterns of NtFT during the annual cycle and reproductive development under different temperature regimes were analysed using quantitative reverse transcription-PCR (qRT-PCR) and RNA in situ hybridization. During floral induction, NtFT was not expressed in bulb scales, roots, or foliage leaves, but it was detected inside the bulb in the apical meristem and leaf primordia. The expression of another key flowering gene, NLF, the LEAFY homologue in N. tazetta, was also observed only in meristem and leaf primordia within the bulbs; however, its expression did not coincide with that of NtFT during meristem transition to reproductive stage. Under high temperatures (25-30 °C) in the dark, NtFT expression occurred simultaneously with floral induction timing, indicating that floral induction is affected by high temperatures but not by photoperiod or vernalization. Monitoring the apical meristem of Narcissus in February-August of two growing seasons under ambient and controlled storage conditions showed that transition to flowering is temperature dependent and varies between years. Lack of NtFT and NLF expression in foliage leaves suggests that flower initiation control in Narcissus differs from that in common model plants.
Project description: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 F3'5'H 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.
Project description:R2R3-MYB transcription factors play important roles in the regulation of plant flavonoid metabolites. In the current study, NtMYB3, a novel R2R3-MYB transcriptional factor isolated from Chinese narcissus (Narcissus tazetta L. var. chinensis), was functionally characterized. Phylogenetic analysis indicated that NtMYB3 belongs to the AtMYB4-like clade, which includes repressor MYBs involved in the regulation of flavonoid biosynthesis. Transient assays showed that NtMYB3 significantly reduced red pigmentation induced by the potato anthocyanin activator StMYB-AN1 in agro-infiltrated leaves of tobacco. Over-expression of NtMYB3 decreased the red color of transgenic tobacco flowers, with qRT-PCR analysis showing that NtMYB3 repressed the expression levels of genes involved in anthocyanin and flavonol biosynthesis. However, the proanthocyanin content in flowers of transgenic tobacco increased as compared to wild type. NtMYB3 showed expression in all examined narcissus tissues; the expression level in basal plates of the bulb was highest. A 968 bp promoter fragment of narcissus FLS (NtFLS) was cloned, and transient expression and dual luciferase assays showed NtMYB3 repressed the promoter activity. These results reveal that NtMYB3 is involved in the regulation of flavonoid biosynthesis in narcissus by repressing the biosynthesis of flavonols, and this leads to proanthocyanin accumulation in the basal plate of narcissus.
Project description:Narcissus plants (Narcissus tazetta var. chinensis) showing mosaic or striping leaves were collected from around Japan, and tested for virus infections using potyvirus-specific primers. Many were found to be infected with a macluravirus and mixtures of different potyviruses, one third of them narcissus yellow stripe virus (NYSV)-like viruses. Genomes of nine of the NYSV-like viruses were sequenced and, together with four already published, provided data for phylogenetic and pairwise identity analyses of their place in the turnip mosaic virus (TuMV) phylogenetic group. Using existing ICTV criteria for defining potyvirus species, the narcissus viruses in TuMV group were found to be from five species; the previously described NLSYV, and four new species we call narcissus virus 1 (NV-1) and narcissus yellow stripe-1 to -3 (NYSV-1, NYSV-2 and NYSV-3). However, as all are from a single host species, and natural recombinants with NV-1 and NYSV-3 'parents have been found in China and India, we also conclude that they could be considered to be members of a single mega-species, narcissus virus; the criteria for defining such a potyvirus species would then be that their polyprotein sequences have greater than 69% identical nucleotides and greater than 75% identical amino acids.