ROSINA (RSI), a novel protein with DNA-binding capacity, acts during floral organ development in Antirrhinum majus

Petal and stamen identity of the Antirrhinum majus flower is under the genetic control of the floral homeotic gene DEFICIENS (DEF). To isolate factors involved in the regulation of DEF gene activity, a promoter segment of this B-function gene, containing cis-acting regulatory elements, was used to identify the novel trans-acting factor ROSINA (RSI). RSI does not show an extended similarity with any gene product present in the database. Rather RSI constitutes a protein that contains domains similar to known proteins from organisms of different phyla. The capacity of RSI to bind a sequence element of the DEF promoter, its spatial and temporal expression pattern together with the phenotype of RSI-RNAi interference plants as well as RSI over-expression in Arabidopsis thaliana suggest that RSI is a putative regulator of DEF gene activity in A. majus.     

Interaction between the Tam1 and Tam2 transposable elements of Antirrhinum majus

Summary Two stable derivatives of the highly unstable niv-53::Tam1 allele of Antirrhinum majus were analysed. In both derivatives the Tam1 element is integrated at the same site and in the same orientation as in the parental niv-53::Tam1 allele. In both cases the Tam1 element was found to carry a 5 bp deletion (CACTA) in one of its termini. This explains the excision deficiency of these two alleles of Tam1, niv-53::Tam1-46 and niv-53::Tam1-49. Niv-44::Tam2, another stable nivea mutation, carries the 5 kb element Tam2, which is not a derivative of Tam1 but possesses identical terminal inverted repeats. When the stable lines 46 and 49 were corssed with line 44, suprisingly, a high number of the flowers in the F₁ displayed a variegated phenotype. Sequence analysis of two germinal revertants isolated from the heterozygote niv-53::Tam1-46/niv-44::Tam2 shows excision of the Tam2 element. This indicates that Tam2 is a defective element, which can be complemented by an active Tam1 element. However, the variegated F₁ phenotype observed is not inherited monofactorially. Variegation is seen only at particular times of development of the F₁ plants. These phenomena seem to involve both the Tam1 and Tam2 transposable elements.     

TheSfm system of gene control inAntirrhinum majus

InAntirrhinum majus,pal-rec, an allele of thepallida series, is considered to be involved in anthocyanin production. Thepal-rec gene normally mutates autonomously from the recessive condition to the dominant giving fully pigmentedPal spots on a colorless background. TheSfm element, when inserted at thepal locus, destabilizes the activity of thepal-rec gene in such a way that the repressor (Sf) component abolishes gene activity in almost all of the cell lineages, whereas the mutator (m) acts to release full gene expression in some of the cells. Such a flip-flop control of thepal-rec results in what is known as shifting.     

Evolution of novel morphological and reproductive traits in a clade containing Antirrhinum majus (Scrophulariaceae)

Phylogenetic analysis of DNA sequences of the chloroplast genes rcbL and ndhf revealed a highly supported clade composed of the families Plantaginaceae, Callitrichaceae, and Hippuridaceae in close association with the model organism Antirrhinum majus and other members of family Scrophulariaceae. Plantago has miniature actinomorphic wind-pollinated flowers that have evolved from zygomorphic animal-pollinated precursors. The aquatic Hippuridaceae have reduced windpollinated flowers with one reproductive organ per whorl, and three, rather than four, whorls. In monoecious aquatic Callitrichaceae, further reduction has occurred such that there is only one whorl per flower containing a single stamen or carpel. Optimization of character states showed that these families descended from an ancestor similar to Antirrhinum majus. Recent studies of plant developmental genetics have focused on distantly related species. Differences in the molecular mechanisms controlling floral development between model organisms are difficult to interpret due to phylogenetic distance. In order to understand evolutionary changes in floral morphology in terms of their underlying genetic processes, closely related species exhibiting morphological Variation should be examined. Studies of genes that regulate morphogenesis in the clade described here could aid in the elucidation of a general model tot such fundamental issues as how changes in floral symmetry, organ number, and whorl number are achieved, as well as providing insight on the evolution of dicliny and associated changes in pollination syndrome.     

金鱼草基因转化和转基因植株再生

本实验采用根癌农杆菌ＬＢＡ４４０４（ｐ３５ＳＧＵＳＩＮＴ与金鱼草下胚轴切段共培养,将ＧＵＳ基因导入金鱼草细胞,通过不定芽发生途径获得抗Ｇ４１８再生植株．经ＤＮＡ／ＤＮＡ斑点杂交及ＧＵＳ活性原位组织检测初步证实外源基因ＧＵＳ已整合进金鱼草基因组并得到表达．     

Detection of point mutations in chloroplast genes of Antirrhinum majus L. I. Identification of a point mutation in the psaB gene of a photosystem I plastome mutant

A point mutation in the plastome-encoded psaB gene of the mutant en:alba-1 of Antirrhinum majus L. was identified by an analysis of chloroplast DNA with a modified PCR-SSCP technique. Application of this technique is indicated when a gene or a group of genes is known in which the point mutation is located. Analysis of primary photosynthetic reactions in the yellowish white plastome mutant indicated a dysfunction of photosystem (PS) 1. The peak wavelength of PS I-dependent chlorophyll (Chl) fluorescence emission at 77 K was shifted by 4 nm to 730 nm, as compared to fluorescence from wild-type. There were no redox transients of the reaction center Chl P₇₀₀ upon illumination of leaves with continuous far-red light or with rate-saturating flashes of white light. The PS I reaction center proteins PsaA and PsaB are not detectable by SDS-PAGE in mutant plastids. Hence, plastome encoded PS I genes were regarded as putative sites of mutation. In order to identify plastome mutations we developed a modified SSCP (single-strand conformation polymorphism) procedure using a large PCR fragment which can be cleaved with various restriction enzymes. When DNA from wild-type and en:alba-1 was submitted to SSCP analysis, a single stranded Hinf I fragment of a PCR product of the psaB gene showed differences in electrophoretic mobility. Sequence analysis revealed that the observed SSCP was caused by a single base substitution at codon 136 (TAT TAG) of the psaB gene. The point mutation produces a new stop codon that leads to a truncated PsaB protein. The results presented indicate that the mutation prevents the assembly of a functional PS I complex. The applicability to other plastome mutants of the new method for detection of point mutations is discussed.     

金鱼草自交不亲和位点位于着丝粒的周边区

在蔷薇科,茄科和玄参科配子体自交不亲和中,编码花柱的SRNase控制花柱的自交不亲和性,在前两科植物中,自交不亲和（S）位点定位于着丝粒的附近,但在玄参科植物金鱼草（Antirrhinum)中自交不亲和位点至今未知,为了确定它在染色体上的位置和基因组结构,以基因型S2S5金鱼草根尖为材料,进行染色体的制备观察,利用地高辛标记的S2RNase和含有其全长的BAC克隆（S2BAC）为探针进行荧光染色体原位杂交（FISH）,发现S2RNase杂交信号位于染色体的着丝粒附近,而S2BAC的杂交信号位于每条染色体的着丝粒的周边区,呈对称的4个,表明金鱼草S位点位于着丝粒的周边区,对S2BAC预测基因的分析表明,发现一个金鱼草新的反转座子（RIS1）。结果显示,金鱼草S位点位于染色体着丝粒的周边区,富含转座子和反转座子,和其他两类配子体自交不亲和的位置类似,预示它们的共同起源和具有抑制重组的功能。     

几种植物生活胚囊的分离与鉴定

向日葵、金鱼草和烟草的成熟胚囊以及前两种植物受精后具原胚和胚乳的胚囊均已从新鲜胚珠中分离出来。干涉差显微观察与 H33258荧光显微技术表明它们确系保持了细胞结构和含有丰富内含物的完整胚囊。荧光素二醋酸酯的显微鉴定进一步证明它们是有生活力的。     

Immobilized copies with a nearly intact structure of the transposon Tam3 in Antirrhinum majus: implications for the cis-element related to the transposition

 In this study we have focused on two copies of the transposon Tam3 isolated from an Antirrhinum majus plant which has flower variegation due to the excision of Tam3 from the nivea locus. These two copies possess a high homology, over 95%, to an active Tam3 element found in the nivea ^{recurrence:Tam3} allele. Although somatic excision of the Tam3 copy from the nivea locus can be detected at 15°C by Southern blotting, neither of the two copies showed any sign of the excision. Both of the immobilized copies were also found in five varieties from different A. majus sources, all of which contain common fragments. The results suggest that the two copies have been fixed in the genomes of many A. majus varieties. Structural differences between these immobilized copies and the known active copy were mainly observed in the subterminal regions, including the terminal inverted repeats. The immobility of the two Tam3 copies might be due to mutations within the end regions of essential cis-elements in Tam3 transposition, as reported for Ac and En/Spm. Received: 30 June 1997 / Accepted: 5 August 1997     

Evidence for correlation between mutability of an unstable anthocyanin-governing locus and abundance of anthocyanin

Summary The pal-rec gene of Antirrhinum majus suppresses anthocyanin except in those cell lines where pal-rec has mutated to Pal, so that anthocyanin-coloured flecks appear on whitish petals. Antirrhinum majus families of very high and very low anthocyanin content (Dark and Pale) were obtained and crossed with two pal-rec pal-rec lines, one with consistently high and the other consistently low mutability. Mutable offspring from Dark parents tended to show higher mutability than those from Pale parents in crosses with either mutable line, providing evidence for an association between intense pigmentation and high mutability. Such an association is discussed in the context of relationship between precursor availability for conversion by a gene product and initiation of activity of that gene.