Blue-grained wheat derived from the hybrid Triticum aestivum L. X Thinopyrum ponticum (Podp.) Barkworth et D. R. Dewey (Agropyron elongatum (Host) P. Beauv., 2n=70). The molecular biological mechanism of the biosynthe...Blue-grained wheat derived from the hybrid Triticum aestivum L. X Thinopyrum ponticum (Podp.) Barkworth et D. R. Dewey (Agropyron elongatum (Host) P. Beauv., 2n=70). The molecular biological mechanism of the biosynthetic pathway of blue pigments in the blue grain remains unclear yet. Dihydroflavonol 4-reductase (DFR) is one of the key enzymes controlling flavonoid synthesis in anthocyanin biosynthetic pathway, and may directly participate in the formation of blue pigment in the aleurone layer of blue-grained wheat. Here we cloned a DFR cDNA (TaDFR) from the developing seeds of blue-grained wheat, and four DFR genomic DNAs from Th. ponticum (ThpDFR.t), blue-grained wheat (TaDFR.bg), white-grained offspring of light blue-grained wheat (TaDFR.wg) and Chinese Spring (2n=42) (TaDFR.csg), respectively. TaDFR cDNA encodes a 354 amino-acids polypeptide with high identity to DFR from Hordeum vulgare L. (94%), Oryza sativa L. (83%), Zea mays L.(84%). The result of cluster analysis showed that TaDFR cDNA nucleotide sequence has 100% identity with that of TaDFR.csg. The four DFR genomic DNAs have extraordinary high homology and each has three introns. The differences of the four DFR genomic DNAs mainly exist in introns. Southern blotting analysis showed that there are at least 3-5 DFR copies in wheat, the copy numbers in different color grain wheats are not significantly different. The hybridization band patterns were the same, but different from that of Th. ponticum. DFR in blue-grained wheat belongs to a DFR superfamily. Northern blotting analysis indicated that the DFR expressed in the developing seeds of both blue- and white-grained wheat at 15 d after flowering (DAF), the mRNA levels of DFR reached the highest at 18 DAF, then declined quickly and disappeared at 33 DAF But the expression levels in blue-grained seeds were higher than that in white grain at the same seed developing stages. DFR transcripts accumulated in young leaves, and leaf sheaths of blue- and white-grained wheat and Th ponticum, but not detected in roots from different color wheats and developing seeds of Th. ponticum. Results indicated that there may exist some regulatory gene(s) which can increase the expression of DFR in the aleurone layer of blue-grained wheat, and thus resulting in the formation of blue pigments.展开更多
In this experiment, floral development from tissue culture of bread wheat (Triticum aestivum L.) was investigated. Immature embryos of 45 wheat cultivars were cultured, and 11.1% of the genotypes regenerated floral or...In this experiment, floral development from tissue culture of bread wheat (Triticum aestivum L.) was investigated. Immature embryos of 45 wheat cultivars were cultured, and 11.1% of the genotypes regenerated floral organs from the calli near the bases of the green buds or plantlets regenerated. The floral buds were morphologically incomplete with the appearances of unisexual pistillate flowers which were naked, clustered with normal ovaries and exuberant feather-like stigmas, but without stamens, paleas, lemmas and glumes. The histological examination showed that the pistils originated from the meristematic cells near the green buds or plantlets, and the clustered pistils were formed by secondary pistillate regeneration. The development of the feather-like structures was earlier than that of the ovules. Biovule developed from an ovary besides normal uniovule. Statistical analysis by X 2 test for independency demonstrated highly significant difference of flower regeneration among the tested genotypes. Wheat cultivar YA-1 revealed higher percentage (44.4%) than other genotypes, and the response could well be repeated in different years. It was indicated that the floral regeneration of immature embryo explants of YA-1 is relatively stable. The frequency of floral regeneration was mainly regulated by the components in the subculture media, compared with the response of the dedifferentiation media, despite the obviously different components involving basal medium type, inorganic Fe2+ concentration and plant growth regulators. The results suggested the combination of 6-benzylaminopurine, alpha-naphthalene acetic-acid and doubled inorganic Fe2+ might be more beneficial to inducing the floral development than that of 2,4-D and normal inorganic Fe2+ concentration in subculture medium. However, both immature inflorescence and mature embryo, as cultured explants of YA-1, did not regenerate any flower organs. It is believed that the immature embryo culture of YA-1 can be used to establish ideal experimental system for the study of floral developmental mechanism in wheat.展开更多
文摘Blue-grained wheat derived from the hybrid Triticum aestivum L. X Thinopyrum ponticum (Podp.) Barkworth et D. R. Dewey (Agropyron elongatum (Host) P. Beauv., 2n=70). The molecular biological mechanism of the biosynthetic pathway of blue pigments in the blue grain remains unclear yet. Dihydroflavonol 4-reductase (DFR) is one of the key enzymes controlling flavonoid synthesis in anthocyanin biosynthetic pathway, and may directly participate in the formation of blue pigment in the aleurone layer of blue-grained wheat. Here we cloned a DFR cDNA (TaDFR) from the developing seeds of blue-grained wheat, and four DFR genomic DNAs from Th. ponticum (ThpDFR.t), blue-grained wheat (TaDFR.bg), white-grained offspring of light blue-grained wheat (TaDFR.wg) and Chinese Spring (2n=42) (TaDFR.csg), respectively. TaDFR cDNA encodes a 354 amino-acids polypeptide with high identity to DFR from Hordeum vulgare L. (94%), Oryza sativa L. (83%), Zea mays L.(84%). The result of cluster analysis showed that TaDFR cDNA nucleotide sequence has 100% identity with that of TaDFR.csg. The four DFR genomic DNAs have extraordinary high homology and each has three introns. The differences of the four DFR genomic DNAs mainly exist in introns. Southern blotting analysis showed that there are at least 3-5 DFR copies in wheat, the copy numbers in different color grain wheats are not significantly different. The hybridization band patterns were the same, but different from that of Th. ponticum. DFR in blue-grained wheat belongs to a DFR superfamily. Northern blotting analysis indicated that the DFR expressed in the developing seeds of both blue- and white-grained wheat at 15 d after flowering (DAF), the mRNA levels of DFR reached the highest at 18 DAF, then declined quickly and disappeared at 33 DAF But the expression levels in blue-grained seeds were higher than that in white grain at the same seed developing stages. DFR transcripts accumulated in young leaves, and leaf sheaths of blue- and white-grained wheat and Th ponticum, but not detected in roots from different color wheats and developing seeds of Th. ponticum. Results indicated that there may exist some regulatory gene(s) which can increase the expression of DFR in the aleurone layer of blue-grained wheat, and thus resulting in the formation of blue pigments.
文摘In this experiment, floral development from tissue culture of bread wheat (Triticum aestivum L.) was investigated. Immature embryos of 45 wheat cultivars were cultured, and 11.1% of the genotypes regenerated floral organs from the calli near the bases of the green buds or plantlets regenerated. The floral buds were morphologically incomplete with the appearances of unisexual pistillate flowers which were naked, clustered with normal ovaries and exuberant feather-like stigmas, but without stamens, paleas, lemmas and glumes. The histological examination showed that the pistils originated from the meristematic cells near the green buds or plantlets, and the clustered pistils were formed by secondary pistillate regeneration. The development of the feather-like structures was earlier than that of the ovules. Biovule developed from an ovary besides normal uniovule. Statistical analysis by X 2 test for independency demonstrated highly significant difference of flower regeneration among the tested genotypes. Wheat cultivar YA-1 revealed higher percentage (44.4%) than other genotypes, and the response could well be repeated in different years. It was indicated that the floral regeneration of immature embryo explants of YA-1 is relatively stable. The frequency of floral regeneration was mainly regulated by the components in the subculture media, compared with the response of the dedifferentiation media, despite the obviously different components involving basal medium type, inorganic Fe2+ concentration and plant growth regulators. The results suggested the combination of 6-benzylaminopurine, alpha-naphthalene acetic-acid and doubled inorganic Fe2+ might be more beneficial to inducing the floral development than that of 2,4-D and normal inorganic Fe2+ concentration in subculture medium. However, both immature inflorescence and mature embryo, as cultured explants of YA-1, did not regenerate any flower organs. It is believed that the immature embryo culture of YA-1 can be used to establish ideal experimental system for the study of floral developmental mechanism in wheat.
