Amaryllidaceae, a monocot plant family, consists of many important ornamental bulb flower species. Chinese narcissus （Narcissus tazetta var. chinensis Roem）, its flowers developed at high temperatures and bloomed at...Amaryllidaceae, a monocot plant family, consists of many important ornamental bulb flower species. Chinese narcissus （Narcissus tazetta var. chinensis Roem）, its flowers developed at high temperatures and bloomed at lower temperatures during the Chinese Spring Festival, is a traditional Chinese flower with high economic and ornamental value. To study its flower development, a full length cDNA containing MADS box domain from narcissus was isolated by a reverse transcription polymerase chain reaction （RT-PCR） with degenerate oligo-nucleotide primers derived from a conserved MADS- and K-box domain sequence. The 5＇ and the 3＇ regions of the gene were amplified using the PCR protocol for the rapid amplification of cDNA ends （RACE）. The 690 bp open reading frame encodes 230 amino acid residues. A comparison of the deduced amino acid sequence of NTAG with the sequence of other MADS box proteins showed 91.3% amino acid identities with HAG （Hyacinthus orientalis）. Sequence analysis and alignment showed significant similarity with other AG homologues. RNA blot analysis indicated that the narcissus NTAG gene was expressed only in reproductive organs, especially in stamens and carpels. These results indicated that the NTAG gene was an AG homologue and that the AG genes appeared to be structurally and functionally conserved between dicots and monocots.展开更多
Chinese narcissus(Narcissus tazetta var.chinensis Roem)blooms but has no seeds.Embryological studies on the species were conducted to discover the causes of its sterility.Its anther wall is composed of four layers of ...Chinese narcissus(Narcissus tazetta var.chinensis Roem)blooms but has no seeds.Embryological studies on the species were conducted to discover the causes of its sterility.Its anther wall is composed of four layers of cells,and its tapetum is of the secretory type.The cytokinesis of microspore mother cells is of the successive type,and the tetrad is tetrahedral.During meiosis of microspore mother cells,some chromosomes lagged,and several micronuclei were found in tetrads.Only 27.7%of the pollen grains contained full cytoplasm,and 1.3%of them germinated in culture medium.No pollen grain,however,could germinate on the stigma.The ovary is trilocular with axile placenta,and the ovules are bitegmic,tenuinucellate,and anatropous.Its embryo sac is of the polygonum type.Most embryo sacs degenerated,and only about 4.5%of the ovules contained a normal embryo sac with an egg cell,two synergids,three antipodal,and a central cell containing two polar nuclei.One reason for the sterility of Chinese narcissus is the abnormality of microsporogenesis and megasporogenesis,in which only a few functional pollen grains and embryo sacs are produced.The other reason is that the pollen grains cannot germinate on the stigma.展开更多
文摘Amaryllidaceae, a monocot plant family, consists of many important ornamental bulb flower species. Chinese narcissus （Narcissus tazetta var. chinensis Roem）, its flowers developed at high temperatures and bloomed at lower temperatures during the Chinese Spring Festival, is a traditional Chinese flower with high economic and ornamental value. To study its flower development, a full length cDNA containing MADS box domain from narcissus was isolated by a reverse transcription polymerase chain reaction （RT-PCR） with degenerate oligo-nucleotide primers derived from a conserved MADS- and K-box domain sequence. The 5＇ and the 3＇ regions of the gene were amplified using the PCR protocol for the rapid amplification of cDNA ends （RACE）. The 690 bp open reading frame encodes 230 amino acid residues. A comparison of the deduced amino acid sequence of NTAG with the sequence of other MADS box proteins showed 91.3% amino acid identities with HAG （Hyacinthus orientalis）. Sequence analysis and alignment showed significant similarity with other AG homologues. RNA blot analysis indicated that the narcissus NTAG gene was expressed only in reproductive organs, especially in stamens and carpels. These results indicated that the NTAG gene was an AG homologue and that the AG genes appeared to be structurally and functionally conserved between dicots and monocots.
基金supported by the Fujian Natural Sciences Foundation (No.F0210009).
文摘Chinese narcissus(Narcissus tazetta var.chinensis Roem)blooms but has no seeds.Embryological studies on the species were conducted to discover the causes of its sterility.Its anther wall is composed of four layers of cells,and its tapetum is of the secretory type.The cytokinesis of microspore mother cells is of the successive type,and the tetrad is tetrahedral.During meiosis of microspore mother cells,some chromosomes lagged,and several micronuclei were found in tetrads.Only 27.7%of the pollen grains contained full cytoplasm,and 1.3%of them germinated in culture medium.No pollen grain,however,could germinate on the stigma.The ovary is trilocular with axile placenta,and the ovules are bitegmic,tenuinucellate,and anatropous.Its embryo sac is of the polygonum type.Most embryo sacs degenerated,and only about 4.5%of the ovules contained a normal embryo sac with an egg cell,two synergids,three antipodal,and a central cell containing two polar nuclei.One reason for the sterility of Chinese narcissus is the abnormality of microsporogenesis and megasporogenesis,in which only a few functional pollen grains and embryo sacs are produced.The other reason is that the pollen grains cannot germinate on the stigma.
