Regeneration of plants from Antirrhinum majus L. callus

Somaclone production in Antirrhinum majus plants by regeneration of plants from callus cultures has been achieved using three types of explant tissue. Regeneration from mature stem internode-derived callus was extremely poor. Callus derived from seedling shoot tips could be induced to form new shoots in six of seven cultivars tested. Regeneration was achieved in all seven cultivars when callus was produced from segments of hypocotyl and was most effective using agar-solidified medium containing 0.25 mgl^-1 naphthoxyacetic acid + 10% coconut milk. In this case, five of the cultivars produced shoots directly, one produced leaves from the petioles of which new shoots emerged, and one regenerated plants chiefly through the production of embryoids.     

Molecular cytogenetic characterization of the Antirrhinum majus genome

As a model system in classical plant genetics, the genus Antirrhinum has been well studied, especially in gametophytic self-incompatibility, flower development biology, and transposon-induced mutation. In contrast to the advances in genetic and molecular studies, little is known about Antirrhinum cytogenetics. In this study, we isolated two tandem repetitive sequences, CentA1 and CentA2, from the centromeric regions of Antirrhinum chromosomes. A standard karyotype has been established by anchoring these centromeric repeats on meiotic pachytene chromosome using FISH. An ideogram based on the DAPI-staining pattern of pachytene chromosomes was developed to depict the distribution of heterochromatin in the Antirrhinum majus genome. To integrate the genetic and chromosomal maps, we selected one or two molecular markers from each linkage group to screen an Antirrhinum transformation-competent artificial chromosome (TAC) library. These genetically anchored TAC clones were labeled as FISH probes to hybridize to pachytene chromosomes of A. majus. As a result, the relationship between chromosomes and the linkage groups (LGs) in Antirrhinum has been established.     

金鱼草AmHMGS基因的克隆及表达特征分析

植物萜烯类化合物合成主要通过MVA和MEP途径,这些萜烯类化合物在植物生长、发育过程发挥着重要作用,萜烯类化合物在植物花香挥发成分中占有大比率.3-羟基-3-甲基戊二酰辅酶A合成酶基因(HMGS)是MVA途径中的关键酶基因,该酶作用主要是催化底物乙酰辅酶A和乙酰乙酰辅酶A生成3-羟基-3-甲基戊二酰辅酶A(HMG-CoA),是合成萜烯类化合物的前体限速酶.本研究以'马里兰'金鱼草(Antirrhinum majus'Maryland')为材料,克隆AmHMGS,基因全长1 383 bp,编码460个氨基酸,时空和组织特异性RT-qPCR表达分析表明,AmHMGS基因在花中表达量显著高于根茎叶;初开期的表达量最高;在盛花期的不同花器官中,AmHMGS基因在雄蕊和上瓣中表达量最高,与其它花器官中的表达量差异显著.用茉莉酸抑制剂不同浓度的菲尼酮处理盛开期金鱼草花瓣,RT-qPCR分析HMGS基因表达量结果表明,菲尼酮处理后能抑制该基因的表达.本研究的结果为明确AmHMGS基因在金鱼草中的表达模式,为今后研究该基因的功能及其在金鱼草花香释放中的信号作用奠定基础.     

Transformation of Antirrhinum majus using Agrobacterium rhizogenes

Hairy roots were produced following the co-cultivation of Agrobacteriumrhizogenes cells with hypocotyls of five varieties of Antirrhinummajus. The use of a strain containing a binary plasmid withT-DNA bearing the ß-glucuronidase reporter gene resultedin the co-transformation of some root clones. Regeneration ofshoots from hairy roots occurred only with variety Golden Monarch.Regenerated plants, some of which were GUS-positive, exhibitedthe abnormal morphology common among hairy root regenerants;they were dwarfed, had an altered leaf shape, a poor root systemand were very delayed in their flowering. Attempts to allowsegregation of the two introduced T-DNAs during crossing ofprimary co-transformants with wild-type plants were not successfulsince all GUS-positive progeny possessed the abnormal morphology.However, ‘semi-dwarf’ plants with morphology muchmore similar to wild-type were produced by the vegetative propagationof selected side-shoots from the transformants. Key words: Antirrhinum, Agrobacterium rhizogenes, transformation, hairy roots     

Cloning and Characterization of a Foldback DNA Element from Antirrhinum majus

A fold back sequence linked to a copy of the transposable element, Tam2, has been Isolated, from a genomic library constructed using partially digested and size-fractionated Antirrhinum DNA Into λ EMBL4 vector, by using Tam2 specific probe. The fold back sequence visualized by heteroduplex analysis reveals a typical stem-loop structure. The foldback element is around 1.2 kb with an average of 227 bp of Inverted termini forming the stem.     

Environmental control of flowering time in Antirrhinum majus

The effect of different environmental conditions on flowering time and the number of leaves produced before the first flower is formed has been investigated in Antirrhinum majus L. The effect of light quality has been tested by decreasing the red/far‐red ratio, generally resulting in a reduced flowering time and leaf number. Furthermore, it could be shown that photoperiod, temperature and light intensity are inversely correlated with flowering time and leaf number. However, lowering the temperature from 15 to 12°C resulted in a reduction of flowering time. This observation shows that Antirrhinum can be vernalised.
Using defined combinations of the four environmental factors we have been able to reduce flowering time to only 42 days or to delay flowering for at least 2 years. The results obtained allow an optimisation of the screening conditions for identifying flowering time mutants in Antirrhinum .     

Transmission of plastids by pollen in Antirrhinum majus

Summary Up to now Antirrhinum was classified as a typical example for a uniparentalmaternal inheritance of the plastids. However, the findings reported here prove that also the male gametophyte of Antirrhinum may occasionally transmit plastids into the egg. This conclusion is based on genetic experiments involving a form of the plastom mutant prasinizans which is described as gelbgrüne prasinizans. In contrast to all other plastid mutations known in Antirrhinum majus this mutant originated in Sippe 50 is completely viable. In plants containing plastids of this mutant type only, the mutant character is manifested during early growth stages. Cotyledons and first foliage leaves which are initially white or white yellow, slowly turn green and become indistinguishable from normal Sippe 50. Reciprocal crosses of green Sippe 50 with gelbgrüne prasinizans gave few variegated descendants; the others were exclusively plants identical with the maternal parent as far as leaf colour is concerned (Table). The variegated individuals cannot be gene mutants since selfing and crossing experiments showed non-mendelian inheritance. Furthermore it could be ruled out that in the cross Sippe 50 x gelbgrüne prasinizans the three variegated descendants represent spontaneous new plastom mutants because the pale tissue in these plants turned green in the same way as the paternal parent. Because of the typical greening of this mutant and since plastid mutations could be ruled out we have to conclude that plastids were transmitted by the pollen parent into the egg. There these plastids multiplied together with the maternal plastids giving rise to the chimeras after sorting-out of the two plastid types. This interpretation is supported by the observation of mixed cells in tissues where the leaf variegation is finely mosaiced. The results were possible only because the plastids of the pollen parent can be unequivocally recognised.