Sensitivity of Geraldton waxflower to ethylene-induced flower abscission is reduced at low temperature

Summary

Exposure to ethylene gas elicits flower abscission from cut stems of Geraldton waxflower (Chamelaucium uncinatum Schauer). Ethylene response rates in plants are mediated by temperature. At 20°C, flower abscission from waxflower ‘Purple Pride’ occurred upon 12 h exposure to 1 µ11^–1 ethylene. This ethylene treatment did not cause flower abscission at either 10 or 2°C. Moreover, flowers held at 2°C were insensitive to 48 h exposure to 1, 10 and 100 µ11^–1 ethylene. However, increasing the duration of treatment with 1 µ11^–1 ethylene at 10 and 2°C to 48 and 144 h, respectively, induced flower abscission. When flowers were held at 20°C in air without exogenous ethylene following continuous exposure to 1 µ11^–1 ethylene at 2°C, the duration required to elicit flower abscission was reduced from 144 to 72 h. Collectively, these responses show that maintaining harvested waxflower at low temperature (e.g. 2°C) is an effective means to minimise ethylene-mediated flower abscission.     

The susceptibility of pepper (Capsicum annuum) to heat induced flower abscission: Possible involvement of ethylene

SUMMARY

Heat stress causes abscission of flowers in pepper plants and thus reduces yield. In the present study, we investigated the involvement of ethylene in heat-stress related flower abscission, by comparing the response of flowers of bell pepper, cv. Maor, known to be sensitive to flower abscission, and flowers of paprika, cv. Lehava, a resistant cultivar of Capsicum annuum. Their differing susceptibilities to high temperatures depend on light. Under high-temperature, high-light conditions, bell pepper was less susceptible than paprika, but, under high-temperature low-light, bell pepper was more susceptible. At high temperatures, flower explant abscission was much higher with bell pepper than paprika. Ethylene production (EP) by bell pepper explants reached a maximum at 34°C and decreased at higher temperatures (42 and 48 C), while in paprika EP rates were lower and reached the maximum at 42°C. Explants of bell pepper flowers were more susceptible to exogenous ethephon than paprika flowers. The sensitivity of a collection of pepper cul-tivars to heat induced flower abscission was more closely correlated with their flower sensitivity to ethephon than with the flower EP rate. We suggest that the differential susceptibility of bell pepper and paprika to heat stress is a result of both different ethylene production by their flowers and their differing sensitivities to ethylene produced under high-temperature stress. However, the sensitivity of the flower to ethylene may be more important in inducing their abscission.     

月季扩张素蛋白基因在花朵开放过程中的表达及功能分析

以切花月季‘Samantha’为试材,明确了外层花瓣主要在花朵开放前期扩展。从花瓣中克隆鉴定了3个具有α亚族扩张素保守特征域的基因：RhEXPA5、RhEXPA6和RhEXPA7。在月季花朵1 ~ 6级的开放过程中,3个扩张素蛋白基因都有表达,其中RhEXPA7的表达与花瓣快速扩展密切关联;在2级花朵花瓣中RhEXPA5和RhEXPA6的表达几乎不受乙烯影响,而RhEXPA7的表达被乙烯显著抑制。进一步利用35S启动子在拟南芥中过表达RhEXPA7,采用外源ACC处理可明显增加转基因植株幼苗的根毛密度;转RhEXPA7基因种子萌发对ABA的敏感性明显降低,而对NaCl的胁迫耐性明显增加。RhEXPA7与月季花朵开放中花瓣快速扩展进程密切关联,参与了乙烯信号的响应,并可以提高过表达拟南芥的胁迫耐性。     

利用DAD1反义片段转化创建菜薹可调控雄性不育材料

 菜薹因为没有好的雄性不育材料或自交不亲和系,至今尚无一代杂种用于生产,根据拟南芥及白菜型油菜的花药不开裂基因DAD1的保守序列设计引物,扩增菜薹的DAD1基因片段（DAD1F）,构建反义DAD1F植物表达载体,用农杆菌介导法转化菜薹,对转基因植株进行分子检测,鉴定其雄性不育性并进行育性恢复试验.克隆得到的菜薹的DAD1基因片段大小为678 bp,命名为BrcpDAD1F,其序列与拟南芥和白菜型油菜的DAD1高度同源,同源率分别为88％和99％;共得到了12株转基因植株,有6株在转录水平上得到表达,表现为雄性不育,花器官畸形,花粉活力低,萌发率不到10％,且开花后不能结角果或结空角果,或者得到极少种子但种子不萌发;用对照的花粉给转基因植株授粉可使其正常结实.以500 μmol·L^-1茉莉酸甲酯处理可使其雄性不育得到恢复,花粉可以在柱头和培养基上萌发,具有受精能力。T₁代可育株与不育株的比例都呈1:3分离, T₂代不同株系的育性分离比例不同,有些株系继续呈1:3的分离,有些株系全是可育株或全是不育株,说明反义抑制呈单基因稳定遗传。     

Ethylene Production During Senescence of Flowers

A method of determining ethylene production by detached flowers is described. A surge of ethylene has been shown to accompany the wilting of carnation flowers at the end of senescence. This surge is independent of fungal infection and it is concluded that in the infected flower the major source of ethylene production is the host tissues.

A similar surge of ethylene production has been observed when the inflorescence wilts on the plant between 20 and 40 days from flower opening.

At temperatures above 7·2° C. (45° F.) the ethylene surge was accompanied by collapse of the petals and rapid loss of water. Cut flowers kept continuously below 7·2° C. slowly declined in weight, the petals became flaccid and ethylene production was negligible. Infection of the flowers with fungus did not materially alter the effect of temperature on the ethylene production.     

Optimising parameters for biolistic gun-mediated genetic transformation of tea [Camellia sinensis (L.) O. Kuntze]

Summary

Genetic improvement of tea through breeding is difficult. Therefore, transgenic tea plants expressing the osmotin gene from Nicotiana tabacum were produced using parameters optimised for biolistic-gun mediated transformation. During optimisation, a total of 4,500 somatic embryos were bombarded using nine combinations of variable target distances and burst pressures, while keeping the gap distance (0.6 cm) and macrocarrier flight distance (16 mm) constant.A total of 90 independent, PCR-positive lines were generated. Southern hybridisation confirmed integration of the osmotin gene in 26 out of 27 PCR-positive lines (three independent lines from each of the nine parameter combinations were selected at random). Statistical analysis revealed that the efficiency of transgene integration was significantly affected by target distance. Only those lines derived from somatic embryos bombarded with 1.0 µg plasmid DNA using a 7.58 MPa burst pressure and 9-cm target distance showed osmotin expression. This was evident from strong northern hybridisation and RT-PCR signals. Leaves of 4-year-old transgenic plants growing in a contained polythene tunnel showed improved osmotic adjustment in response to osmotic stress imposed by NaCl. The osmotic potentials of transgenic leaves immersed in 100 mM or 200 mM NaCl solutions were more negative than those of non-transformed control leaves.     

Effects of high temperature on flower colour and anthocyanin content in pink flower genotypes of greenhouse chrysanthemum (Chrysanthemum morifolium Ramat.)

Summary

The relationship between the intensity of flower colour and changes in the content of the main anthocyanins under various controlled temperatures was examined in order to clarify the effects of high temperature on flower colouration in six pink flower genotypes of greenhouse chrysanthemum (Chrysanthemum morifolium Ramat.). Poor colouration of flowers was observed at 30°C in all genotypes except ‘Chatoo’. This genotype showed little difference in flower colour between different temperature treatments. The degree of change in flower colour differed depending on the genotype, whereas no clear differences in flower colouring were observed between Summer – Autumn flowering and Autumn-flowering genotypes. All genotypes showed lower contents of the two anthocyanins tested [cyanidin 3-O-(6’’-O-monomalonyl- -glucopyranoside) and cyanidin 3-O-(3’’,6’’-O-dimalonyl- -glucopyranoside)] at higher temperatures. Therefore, flower colour changes were attributable to changes in these two main anthocyanins. Differences in colouration between genotypes and temperature conditions were also detectable in values that were measured using a colorimeter. Changed parameters that were visually verifiable were the a* value, representing the degree of red colour, and the C* value, representing chroma. For ‘Sei-Monako’, which showed visually greater differences between temperature treatments, the a* and C* values were low under high temperature conditions. On the other hand, in ‘Chatoo’, the differences detected by eye and those in a* and C* values between temperature treatments were small. In addition, the present results indicate that mean temperature is more important than either day or night temperature in determining the degree of flower colouration.     

Genetic diversity analysis of Phalaenopsis ‘Frigdaas Oxford’ using SRAP markers with reference to those genes responsible for variations in the pigmentation of petals and sepals

Summary

A selfed progeny from Phalaenopsis ‘Frigdaas Oxford’, with yellow flowers and red-purple blotches, was established. Individual plants varied greatly in terms of the number, size, and distribution pattern of the red-purple blotches. Sequence-related amplified polymorphism (SRAP) markers were used to analyse 159 individual plants in the progeny, and 14 polymorphic primer combinations were selected from the 594 SRAP primer combinations tested. In total, 80 polymorphic bands were produced using these primer combinations. On average, each primer pair combination amplified 80.1% polymorphic bands. An UPGMA dendrogram and a principal coordinate analysis (PCA) showed that the 159 individual plants selected could be divided into 12 clusters, including a cluster that consisted of plants in which the petals and sepals were fully red-purple in colour. Plants in which the petals and sepals had large red-purple blotches were genetically closer to the latter cluster than were those plants in which the blotches were small, indicating that the SRAP markers could be used efficiently to identify genetic variation in a Phalaenopsis population with respect to flower colour. Furthermore, 45 unique genes identified by SRAP from the selfed progeny population were sequenced. These data suggest that SRAP markers for the pattern of pigmentation in the petals and sepals of Phalaenopsis may be used in breeding Phalaenopsis for specific patterns of flower pigmentation.     

异源表达拟南芥赤霉素2–氧化酶基因对矮牵牛形态发育的影响

拟南芥赤霉素2–氧化酶基因AtGA2ox1在矮牵牛（Petunia hybrida）中过量表达导致转基因植株开花延迟,株形明显矮化,花冠变小,花冠表皮细胞变小,但花色变化不明显。施用多效唑对矮牵牛花冠的影响与过量表达AtGA2ox1一致。用拟南芥茎特异性表达基因At3g56700的启动子驱动AtGA2ox1在矮牵牛中表达时,转基因植株的表型变化在株系间存在明显的差异,但外源基因在茎中的表达量都明显高于叶和花中的,果实和种子的发育未受影响,通过对转基因后代的筛选可以获得株形矮化,其它性状的发育受影响较小的转基因株系。     

Variation among Kalanchoe species in their flowering responses to photoperiod and short-day cycle number

Summary

Our objectives were to identify the critical daylength and number of short-day (SD) cycles necessary for flowering in Kalanchoe glaucescens, K. manginii, and K. uniflora. In Experiment I, plants were grown for 20 weeks under 9, 10, 11, 12, 13, 14, or 15 h photoperiods at 300 µmol m^–2 s^–1 for 8 h 55 min (9 h photoperiod), or 9 h and extended with dayextension (3 µmol m^–2 s^–1) lighting (10 – 15 h photoperiods). All species flowered when grown under photoperiods ranging from 9 – 12 h. The percentage of flowering plants decreased for all species as the photoperiod increased from 12 h to 14 h. No flowering occurred on plants grown under a 15 h photoperiod. Node numbers below the terminal inflorescence increased from 18 nodes to 28 nodes on K. glaucescens, from 12 nodes to 14 nodes on K. manginii, and from 12 nodes to 16 nodes on K. uniflora as the photoperiod increased from 12 h to 14 h, from 10 h to 12 h, and from

12 h to 13 h, respectively. Total flower numbers on K. uniflora decreased from 45 flowers to 13 flowers as the photoperiod increased from 9 h to 13 h. In Experiment II, plants were exposed to 0, 1, 2, 3, 4, 5, 6, 7, or 8 weeks of SD (8 h photoperiod) before being placed under night-interruption lighting (2 µmol m^–2 s^–1; between 22.00 – 0.200 h). One-hundred percent of K. glaucescens, K. manginii, and K. uniflora plants flowered when they received more than 1, 3, or 6 weeks of SD, respectively. The node number below the terminal inflorescence in each species was not affected by SD cycle-number. Total flower numbers per plant, and days to first open flower, were unaffected as the number of SD cycles exceeded the number required to induce flowering for all species.     

Influence of ethanol on ethylene biosynthesis and flower senescence of cut carnation

Ethanol in the holding-solution inhibited climacteric ethylene (C₂H₄) biosynthesis and decreased the respiration rate 60% during a 7-day period in cut carnation flowers. Conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to C₂H₄ was inhibited by adding ethanol to the holding-solution. Simultaneously, ACC-induced senescence in carnation flowers was inhibited by ethanol. Ethanol was the most effective alcohol in delaying carnation flower senescence of the tested series methanol, ethanol, propanol, tert-butanol and n-butanol. Ovary development was also inhibited in carnation flowers by ethanol. The senescence of Easter lily flowers (Lilium longiflorum) and tulip flowers (Tulipa gesneriana) was not delayed by ethanol.     

Comparative analysis of floral pigmentation between wild-type and white-flowered varieties of Cyclamen graecum

Summary

The flower colour of Cyclamen graecum gra6 (wild-type) is pink-purple in the main part of the petal, referred to as the ‘slip’, and deep purple at the petal base, referred to as the ‘eye’. On the other hand, flowers of C. graecum gra50 (a white-flowered variant) exhibit a white colour in both the ‘slip’ and ‘eye’ regions. In this study, the relationship between floral pigmentation and the expression of several anthocyanin biosynthesis genes was investigated in C. graecum gra6 and gra50. The pigments in the ‘slip’ and ‘eye’ regions consist mainly of malvidin 3,5-diglucoside in gra6, suggesting that the difference between the colour of the ‘slip’ and ‘eye’ regions is related to the amount of anthocyanin present. White-flowered C. graecum gra50 possessed lower amounts of anthocyanins, but higher amounts of flavonols compared to gra6, suggesting a change in metabolism caused by a disruption of anthocyanin biosynthesis. Gene expression analysis demonstrated that expression of the dihydroflavonol 4-reductase gene 2 (CgraDFR2) was lower in gra50 compared with gra6, whereas expression of the three other key genes (dihydroflavonol 4-reductase gene 1, flavonoid 3’,5’-hydroxylase, and anthocyanidin synthase) did not differ greatly. These results suggest that the white-flowered variant (gra50) may result from a defect in expression of the CgraDFR2 gene.     

Virus-induced gene silencing as a tool for functional analyses in the emerging model plant Aquilegia (columbine, Ranunculaceae)

Background  

There is considerable interest in rapid assays or screening systems for assigning gene function. However, analysis of gene function in the flowers of some species is restricted due to the difficulty of producing stably transformed transgenic plants. As a result, experimental approaches based on transient gene expression assays are frequently used. Biolistics has long been used for transient over-expression of genes of interest, but has not been exploited for gene silencing studies. Agrobacterium-infiltration has also been used, but the focus primarily has been on the transient transformation of leaf tissue.     

Soil pasteurization and inoculation with Glomus intraradices alters flower production and bulb composition of Zephyranthes spp.

Summary

We assessed whether adding inoculum of the vesicular-arbuscular mycorrhizal fungus (VAMF) Glomus intraradices into growing medium of three Zephyranthes spp (White Rain Lily [WRL], Z. candida; Pink Fairy Lily [PFL], Z. robusta; Yellow Zephyr Lily [YZL], Z. sulphurea) alters aspects of flower and bulb production. Shoots of inoculated plants emerged 7–13 d earlier than those of non-inoculated plants. Inoculation slightly delayed the emergence of flower buds on WRL and PFL, but did not delay the time of flower opening of WRL. Inoculated YZL flowered 4–11.d earlier than non-inoculated plants. The number of flowers produced by YZL was consistently increased by inoculation, while the inoculation with VAMF increased flower production by WRL and PFL only when plants were growing in pasteurized soil. Leaf biomass of inoculated WRL was larger than non-inoculated plants, while leaf biomass was generally smaller in inoculated PFL and YZL. Partitioning of biomass to bulbs and offsets varied with species, soil pasteurization, and inoculation. Inoculation increased the combined weight of bulbs and offsets at the end of the second growing cycle by 50–150%. Inoculated YZL and WRL consistently produced more offsets in the second growing season after inoculation. For all species, inoculation increased phosphorus and carbohydrates and decreased nitrogen and amino acids in bulbs. Adding VAMF into the growing medium of Zephyranthes altered aspects of plant development and biomass partitioning important to flower and bulb production during the first growing cycle after inoculation, and most effects of VAMF inoculation are more pronounced in the second growing cycle after inoculation. Of the three species examined, Z. sulphurea showed the most consistent responses to inoculation.     

乙烯对‘洛阳红’牡丹切花开放衰老进程及内源乙烯生物合成的影响

 以开花指数为1级的‘洛阳红’牡丹切花为试材,研究了外源乙烯和乙烯作用抑制剂1-甲基环丙烯（1-MCP）处理对其采后开花衰老进程中开花指数、花径增大率、瓶插寿命、内源乙烯生成量及乙烯生物合成关键酶ACC合成酶（ACS）和ACC氧化酶（ACO）活性的影响,从乙烯生物合成角度探讨了乙烯对其采后开花衰老的调节机理。结果表明,10 μL·L^-1乙烯处理6 h明显加快了‘洛阳红’花朵开放进程,缩短了切花的瓶插寿命,并促使其在盛开后出现严重落瓣;1.0 μL·L^-1 1-MCP处理6 h则延缓了花朵开放,延长了瓶插寿命,但却影响了部分切花的充分开放;内源乙烯的生成分别受乙烯和1-MCP处理的促进和抑制,与切花的开放衰老进程密切相关。不同处理后ACS、ACO酶活性分析表明,ACS活性变化与内源乙烯的生成相联系,是影响牡丹切花开放衰老进程的主要因子,这与目前得出的ACS是植物乙烯生物合成限速酶的研究结果相一致。     

Molecular cloning and functional analysis of a flavanone 3-hydroxylase gene from blueberry

Vaccinium corymbosum (blueberry) is touted as a superfood with numerous health benefits due to its high levels of flavonoids. Flavanone 3-hydroxylase (F3H) is a key regulatory enzyme of the flavonoid pathway. In this study, we cloned the full-length cDNA of F3H (designated VcF3H) from young blueberry leaves using rapid amplification of cDNA ends (RACE). The cDNA contained a 1080-bp open reading frame that encoded a 359-amino acid protein. The deduced VcF3H protein showed high similarities to other plant F3Hs. Conserved amino acid motifs required for ferrous iron binding (HXD) and 2-oxoglutarate binding (RXS) were identified in VcF3H, VcFLS (flavonol synthase), and VcANS (anthocyanidin synthase). Quantitative RT-PCR analysis demonstrated that VcF3H was expressed in all tissues tested, with particularly high expression in young leaves, fruits (pink and blue), and stems. Anthocyanins accumulated mainly in fruits, whereas flavonols were found mainly in leaves and stems. Furthermore, the expression pattern of VcF3H was similar to that of VcCHS, VcDFR, and VcANS in various tissues. Heterologous expression of VcF3H in Arabidopsis thaliana increased the anthocyanin content in leaves, but did not affect the flavonol content. Thus, VcF3H seems to be involved in anthocyanin synthesis in the flavonoid biosynthetic pathway when ectopically expressed in Arabidopsis.     

Induction of novel variants through physical and chemical mutagenesis in Barbeton daisy (Gerbera jamesonii Hook.)

Summary

Gerbera (Gerbera jamesonii) is an attractive ornamental flower of high economic importance. The present investigation was aimed at generating novel flower colour variants in the gerbera cultivar ‘Harley’ through physical and chemical mutagenesis. In vitro-raised shoot cultures of gerbera, established from petiole explants, were exposed to different doses of γ-rays (1.5, 2.0, 2.5, 5.0, 10.0, 15.0, 20.0, or 30.0 Gy) using a Cobalt-60 source emitting 2.51 kGy h^–1. To induce mutations through chemical mutagenesis, different concentrations of ethylmethane sulphonate [EMS; 0.1, 0.2, 0.5, 0.8, or 1.0% (v/v)] were administered for 10 min or for 20 min. The LD50 values calculated for shoot survival and the induction of mutations were approx. 6.5 Gy for γ-rays and 0.65% (v/v) EMS for 10 min, or ≤ 0.1% (v/v) EMS for 20 min. Investigations revealed a negative correlation between mutagen dose and plant survival, both in vitro and after acclimatisation. Morphological variants showing changes in leaf shape, leaf size, scape length, flower diameter, and flower colour were obtained. Significantly, early flowering was induced in all mutated plants compared to non-mutated plants.The high frequencies of colour variants obtained using Bγ-rays, or the application of EMS to in vitro-raised shoot cultures could be an effective way to improve gerbera cultivars.     

Effects of chilling on the formation of secondary growing-centres in flowers of the glasshouse carnation

The incidence of secondary growing-centres within the flowers of carnation was increased when plants were chilled at 5°C for 1–3 weeks during flower development. Application of GA₃ to shoots in the early stages of flower formation also caused an increase in the number of secondary growing-centres formed. Shoot tips excised from plants that had been chilled yielded greater amounts of diffusible gibberellin-like substances than shoot tips excised from plants that had been grown at normal glasshouse temperatures. It is suggested that endogenous gibberellins have a role in controlling the formation of secondary growing-centres within the flower.     

Seasonal variation in pigmentation and anthocyanidin phenetics in commercial Eustoma flowers

The seasonal change in petal color and pigmentation of 29 commercial Eustoma cultivars was studied. The flowers are basically divided into four groups according to the major anthocyanidin phenotype in association with petal coloration, i.e., delphinidin (Dp)-based (purple flower), cyanidin (Cy)-based (reddish purple flower), pelargonidin (Pg)-based (pink flower), and none (white flower) groups. The constitution of petal anthocyanidins was not changed by forcing treatment in most of the flowers. Lightness (L^*) and chroma (C^*, color saturation) showed a change along with the increase/decrease of hue angle difference (ΔH^*), thus simultaneously the chromatic tonalities tended to move to redder and bluer, respectively. Floral pigment clustering described two flower groups in a dendrogram, based on anthocyanidin constitutions as phenetic markers, which are apparently the Dp- and Pg-based phenotypes of anthocyanidin syntheses. The Cy-based flowers made a subcluster with the Pg-based flowers, indicating a close relationship in the biosynthesis of the two anthocyanidins, and suggesting the Dp- and Pg-syntheses complement one another.