Genetic interactions in the control of flowering time and reproductive structure development in tomato (Solanum lycopersicum)

Different tomato (Solanum lycopersicum) mutants, affected in flowering time, reproductive structure or plant architecture, were crossed to produce double mutants in order to investigate gene interactions in flowering regulation in this autonomous species with a sympodial growth habit. The compound inflorescence: uniflora, uniflora: self pruning, uniflora: blind, and jointless: uniflora double mutants all produced solitary flowers like their uniflora parent, instead of inflorescences. All double mutants were late flowering. uniflora: blind and uniflora: self pruning had flowering times intermediate between those of their two parents. jointless: uniflora and compound inflorescence: uniflora flowered later than uniflora, the mutant with the most delayed flowering. All double mutants developed strong lateral shoots at node levels approximately corresponding to the level at which their parent cultivars initiated their first reproductive structure, which is a typical trait of uniflora. These results suggest that the UNIFLORA gene acts upstream of the other investigated genes in controlling flowering in tomato, and that floral transition of the primary shoot and floral transition of sympodial segments are regulated differently.     

Flowering in the uniflora mutant of tomato (Lycopersicon esculentum Mill.): description of the reproductive structure and manipulation of flowering time

The uniflora (uf) mutant of tomato (Lycopersicon esculentum Mill.) is known to produce solitary, normal, fertile flowers instead of inflorescences. Histological and SEM studies revealed that this unusual reproductive structure resulted from the inability of the plant to produce an inflorescence and not from post-initiation abortion processes affecting young flower buds. Development prior to floral transition was apparently not affected by the mutation since rates of germination and leaf initiation were identical in both uf and the Ailsa Craig (AC) initial cultivar. However, the time of flowering of the mutant was always delayed as compared to AC. In uf, environmental conditions markedly influenced flowering time which occurred early in all individuals in summer, but was strongly delayed during winter, with less than 20% plants reaching flowering before having initiated 40 leaves. Defoliation treatments stimulated floral transition in uf plants since 100% flowering occurred whatever the season and since the time of floral transition was usually advanced in comparison to the non-defoliated control plants. Similarly, compared to intact uf plants, flowering of terminal meristem of cuttings and upper axillary bud of decapitated plants was promoted. The involvement of correlative influences and assimilate availability in the control of flowering in tomato is suggested by these findings.     

A floral meristem identity gene influences physiological and ecological aspect of floral organogenesis

The architecture of a flower is tightly linked to the way a plant pollinates, making it one of the most physiologically and ecologically important traits of angiosperms. Floral organ development is proposed to be governed by the activity of three different classes of organ identity genes (the ABC model), and the expression of those genes are regulated by a number of meristem identity genes. Here we use a transgenetic strategy to elucidate the role of one floral meristem identify gene,LEAFY (LFY), in the evolution of floral organogenesis of a self pollinatorIdahoa scapigera and a obligatory out-crosserLeavenworthia crassa in the mustard family, Brassicaceae. By introducing theLFY genes from these two types of pollination habit into the genetic model speciesArabidopsis thaliana, we provide evidence that changes inLFY influenced flower architecture probably by controlling the downstream organ identity genes.     

Eucalyptus has a functional equivalent of the Arabidopsis floral meristem identity gene LEAFY

Two genes cloned from Eucalyptus globulus, Eucalyptus LeaFy (ELF1 and ELF2), have sequence homology to the floral meristem identity genes LEAFY from Arabidopsis and FLORICAULA from Antirrhinum. ELF1 is expressed in the developing eucalypt floral organs in a pattern similar to LEAFY while ELF2 appears to be a pseudo gene. ELF1 is expressed strongly in the early floral primordium and then successively in the primordia of sepals, petals, stamens and carpels. It is also expressed in the leaf primordia and young leaves and adult and juvenile trees.The ELF1 promoter coupled to a GUS reporter gene directs expression in transgenic Arabidopsis in a temporal and tissue-specific pattern similar to an equivalent Arabidopsis LEAFY promoter construct. Strong expression is seen in young flower buds and then later in sepals and petals. No expression was seen in rosette leaves or roots of flowering plants or in any non-flowering plants grown under long days. Furthermore, ectopic expression of the ELF1 gene in transgenic Arabidopsis causes the premature conversion of shoots into flowers, as does an equivalent 35S-LFY construct. These data suggest that ELF1 plays a similar role to LFY in flower development and that the basic mechanisms involved in flower initiation and development in Eucalyptus are similar to those in Arabidopsis.     

AGAMOUS-LIKE24 and SHORT VEGETATIVE PHASE determine floral meristem identity in Arabidopsis

The formation of flowers starts when floral meristems develop on the flanks of the inflorescence meristem. In Arabidopsis the identity of floral meristems is promoted and maintained by APETALA1 (AP1) and CAULIFLOWER (CAL). In the ap1 cal double mutant the meristems that develop on the flanks of the inflorescence meristem are unable to establish floral meristem identity and develop as inflorescence meristems on which new inflorescence meristems subsequently proliferate. We demonstrate in contrast to previous models that AGAMOUS-LIKE 24 (AGL24) and SHORT VEGETATIVE PHASE (SVP) are also floral meristem identity genes since the ap1-10 agl24-2 svp-41 triple mutant continuously produces inflorescence meristems in place of flowers. Furthermore, our results explain how AP1 switches from a floral meristem identity factor to a component that controls floral organ identity.     

外源NO与蔗糖对盐胁迫下番茄(Lycopersicon esculentum Mill)幼苗氧化损伤的保护效应

选取长至6～8片真叶的健康番茄(Lycopersicon esculentum Mill)幼苗,分别进行蔗糖、硝普钠(sodium nitropresside, SNP, 作为外源NO供体)及其体积比例组合(1:1)处理;36h后施以NaCl胁迫,并分别于0h(胁迫前)、24h、48h和72h 取样,进行相关生理生化指标测定.具体5个实验处理如下:A. 蒸馏水(CK); B. 100 mmol/L NaCl;C. 0.1 mmol/L SNP 100 mmol/L NaCl;D. 0.1 mmol/L SNP 1.0mmol/L蔗糖 100 mmol/L NaCl; E. 1.0 mmol/L蔗糖 100 mmol/L NaCl.结果表明:与SNP和蔗糖单独处理相比,二者组合处理对缓解盐胁迫下番茄幼苗的氧化损伤存在正协同效应,主要表现在进一步增强了番茄幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)的活性;提高了脯氨酸(Pro)的含量,同时膜脂过氧化产物丙二醛(MDA)含量显著降低(P＜0.05).采用聚丙烯酰胺浓度梯度凝胶电泳对盐胁迫24 h和48 h材料的POD同功酶检测表明,当NaCl单独处理时,番茄幼苗叶片POD同功酶第V条带缺失,其它谱带酶量减少,抑制了POD同功酶的表达;SNP和蔗糖单独处理能够保护盐胁迫(24、48h)所导致的POD同功酶条带的完整;而组合处理既保证了POD同功酶条带的完整,又加强了酶量的表达.随着盐胁迫时间的延长,其氧化损伤程度愈烈,SNP和蔗糖组合处理能够更有效地缓解盐胁迫对番茄幼苗植株造成的氧化损伤.     

Cropping system influences Tomato spotted wilt virus disease development,thrips population and yield of tomato (Lycopersicon esculentum)

Yield of tomato is limited by many diseases including Tomato spotted wilt virus disease. This study was conducted in the field at Kenya Agriculture Research Institute Njoro, Kenya, in 2004 and 2006 to determine the effect of intercropping on disease development, thrips population and yield of tomato variety Cal J grown under four intercrop systems involving kale, onion, maize and sole tomato. The experimental design was a Randomised Complete Block Design (RCBD) replicated three times. Disease scores on tomato–maize differed significantly from tomato–kale and tomato–onion in both years of the study. Maize cropping system had a low significant thrips population from the other cropping systems. Tomato–maize intercrop produced the lowest fruit weights and marketable yield in 2004 and 2006, while yield of onion, kale and maize in intercrops were not significantly different from their monocrops. Land equivalent ratio was >1 in all the cropping systems.     

昼间亚高温下番茄叶中糖含量与蔗糖代谢相关酶的活性日变化

研究番茄品种‘辽园多丽’幼苗在昼间35℃亚高温条件下叶中糖含量及蔗糖代谢相关酶活性日变化的结果表明,昼间亚高温处理后的幼苗叶中果糖、葡萄糖和淀粉含量下降,蔗糖含量升高。与蔗糖代谢相关的酶活性有明显的昼夜节律性变化,转化酶、蔗糖合成酶呈现昼间活性低、夜间活性高的节律性,而蔗糖磷酸合成酶活性在进入夜间时立刻升高。35℃昼间亚高温处理后的幼苗叶中,转化酶活性下降,蔗糖合成酶活性明显升高,蔗糖磷酸合成酶活性则略有升高。     

Influence of nicotianamine and iron supply on formation and elongation of adventitious roots in hypocotyl cuttings of the tomato mutant 'chloronerva' (Lycopersicon esculentum)

The influence of nicotianamine (NA) on formation and elongation of adventitious roots in hypocotyls of de-rooted NA-less mutant seedlings of Lycopersicon esculentum Mill, was examined in relation to the iron supply [ferric N-N'-ethylenediaminedi-(2-hydroxyphenylacetate) (FEDDHA), ferric ethylenediaminetetracetate (FeEDTA), ferric N-(2-hydroxyethyl)-ethylenediaminetriacetate (FeHEDTA, Fe-citrate and FeCl₃] in the nutrient solution. The initiation of root primordia in hypocotyl cuttings was independent of NA and occurred with about the same frequency in both, mutant and wild-type. In the mutant the development of primordia to adventitious roots was blocked at all iron sources used, except FeEDTA. Addition of NA (5x 10⁻⁶ to 2 × 10⁻⁵ M ) to the rooting medium resulted in a fast growth of adventitious roots in mutant cuttings with all iron sources tested. Rooting of wild-type cuttings was independent from NA application and iron sources. We suppose that NA is involved in the intracellular transport of iron. Its function is possibly linked with chelation of ferrous iron in the cell.     

Interaction between photoperiod, photosynthesis and ethylene formation in tomato plants (Lycopersicon esculentum cv. Ailsa Craig and ACC‐oxidase antisense pTOM13)

Wild‐type and ACC‐oxidase antisense tomato plants ( Lycopersicon esculentum Mill. cv. Ailsa Craig and pTOM13) were grown in environment‐controlled rooms for 21 days under photoperiods of 8, 16 or 23.5 h at an irradiance of 300 µmol m⁻² s⁻¹. Photosynthetic pigments, photosynthesis, soluble carbohydrates, starch and ethylene were measured on the last fully expanded leaf. Increasing the photoperiod from 8 to 16 h stimulated all measured growth parameters in both cultivars. However, when the photoperiod was increased to 23.5 h, foliar yellowing and deformation were observed in the wild‐type Ailsa Craig whereas no change was observed in pTOM13. It was not possible to relate these foliar changes in Ailsa Craig to destruction of the photosynthetic apparatus by excess carbohydrate levels in the leaves. Because pTOM13 was antisense to ACC‐oxidase. it is proposed that yellowing and deformation in leaves of wild‐type tomato plants grown under long photoperiods may be caused by stress ethylene induced by a long photoperiod.     

mRNA levels of four tomato (Lycopersicon esculentum Mill. L.) genes related to fluctuating plant and soil water status

Expression of the genes le20, ni3212, le25 and lcyp2 was quantified in relation to soil and plant water status for pot-grown tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig) in a replicated trial in a partially environmentally controlled glasshouse. Leaf water potential, relative water content, stomatal conductance and gravimetric soil water content were measured at 0800,1200 and 1600 h on three days during the imposition of three different watering regimes. Paired leaf samples were analysed for mRNA. Plant-to-plant variability was quantified and partitioned. le20 mRNA was found in all leaves and responded both to short-term diurnal fluctuations in water status and to more severe stress, though with reduced sensitivity to the greatest stresses. An overnight decline in le20 mRNA was independent of soil or plant water status. The pattern of expression for ni3212 was similar though ni3212 mRNA was much more abundant and the overnight drop in expression was not significant. le25 mRNA was only detected where leaf water potential was below ?0.9 MPa and increased linearly with further decline in leaf water potential. lcyp2 was constitutively expressed with a diurnal pattern characterized by a sharp depression at 1600 h but with expression being enhanced by increasing water deficit at all times. The control and significance of the four genes are discussed in relation to the proposed function of their respective gene products.     

Toxicity symptoms caused by high expression of Tet represser in tomato (Lycopersicon esculentum Mill. L.) are alleviated by tetracycline

As a first step towards transferring a tetracycline (Tc)-inducible gene expression system to tomato, we have transformed tomato plants with the Tn10-encoded tet repressor gene (tetR). Homozygous transformed plants with high expression of tetR mRNA show a deleterious phenotype, having reduced shoot dry weights and leaf chlorophyll content, an even more marked reduction in root dry weight and leaf size, and altered photosynthetic physiology. It appears that TetR protein exerts its toxicity only when expressed beyond a threshold level and by interacting with a process that is non-limiting under slow growth conditions. The deleterious phenotype was almost completely reversed by the application of 1 mg dm^?3 Tc to plants grown in sand. The possiblity is discussed that TetR causes these symptoms by binding to a specific DNA sequence functioning as a Tet operator. The effect of Tc on growth and physiology in wild-type plants grown in sand or rockwool is described. Tc at 0.1 mg cm^?3 had no effect. Tc at 1 mg dm^?3 caused a small reduction in root growth, while 5 and 20 mg dm^?3 Tc caused large reductions in growth and photosynthetic parameters.     

Hygienic quality of traditional processing and stability of tomato (Lycopersicon esculentum) puree in Togo

Microbiological and physicochemical qualities of a tomato (Lycopersicon esculentum) puree production line (ripe tomato, washing, cutting, pounding, bleaching, straining, bottling and pasteurization) and its preservation in Togo, West Africa, were studied using the HACCP method. Samples generated during the steps described previously were analyzed by determining sensory, chemical and microbiological characteristics. Samples were analyzed using MPN for coliform populations and plate count methodology for other bacteria. The microorganisms involved in spoilage of the opened products were moulds of genera Penicillium, Aspergillus, Fusarium, Geotrichum, Mucor and gram-positive Bacillus bacteria. The preserved tomato puree exhibited a pH value of 4.3, 90% water content, 0.98 water activity (aw) and an average ascorbic acid level of 27.3mg/100g. Results showed that the critical control point (CCP) of this tomato puree processing line is the pasteurization stage. The analysis of selected microbiological and physicochemical parameters during the preservation of bottled tomato puree indicated that this product was stable over 22 months at 29 degrees C. But the stability of the opened product stored at 29 degrees C did not exceed two months.     

Polyamine levels in pollinated and auxin-induced fruit of tomato (Lycopersicon esculentum) during development

The changes taking place during fruit development in the concentration of the 3 polyamine fractions, i.e. free, perchloric acid-soluble conjugates and perchloric acid-insoluble bound polyamines, were analyzed in tomato fruits ( Lycopersicon esculentum Mill, cv. F121) induced to set by either pollination or auxin application. Before the onset of cell division, total polyamines were 50% higher in auxin-treated fruits than in pollinated ones, most of the polyamines being found as perchloric acid-soluble conjugates in both fruit set treatments. At the onset the level of polyamines in both fruit types was 100 times higher than during cell expansion or ripening. The highest polyamine found during cell division was perchloric acid-soluble conjugated spermidine in both fruit set treatments. After cell division, polyamine concentration was similar in both fruit set treatments. The concentration of polyamines in the jelly was similar in pollinated and auxin-induced fruits during cell expansion but not during ripening. At the onset of ripening there was an increase of one order of magnitude in the concentration of perchloric acid-insoluble bound putrescine in the jelly of pollinated fruits. Polyamines were more than 5-fold higher in unpollinated ovaries than in fruits induced to set by either pollination or auxins. It is suggested that pollinated and parthenocarpic fruits differ in their polyamine metabolism during the initial stages of development, but not after cell division. It is also suggested that polyamines undergo rapid turnover during cell division. Perchloric acid-insoluble bound putrescine might play a role in seed formation in tomatoes.     

UV-B radiation causes early ripening and reduction in size of fruits in two lines of tomato (Lycopersicon esculentum Mill.)

An open-air experiment was performed in Pistoia (Italy) to investigate the possible protective role played by different contents of UV-B absorbing compounds to realistic UV-B supplementation and to study its effect on plant fruit production. A mutant line and its normal counterpart of Lycopersicon esculentum Mill, which differ in the content of UV-B absorbing compounds, were used. Additional UV-B radiation in the field was supplied to simulate a 20% stratospheric ozone depletion. Two groups of plants were grown: ‘control’, where plants received only natural solar UV-B radiation, and ‘UV-B’ treatment, where plants were grown under supplemental UV-B. The results of the experiment showed that the content of UV-B absorbing compounds of treated plants did not differ from that of the control in both lines. This indicates that natural sunlight, in Mediterranean areas, is saturating for synthesis of these compounds also in plants with normal content of UV-B absorbing compounds. Consequently, plants are not able to produce significant additional amounts of them, in response to a realistic UV-B supplementation, in order to protect the plant from additional UV-B radiation. No different responses to the UV-B supplementation were found between the two lines. The most significant UV-B effect was an earlier reddening of fruits in comparison with the ‘control’ accompanied by a reduction in the size of mature fruits. No significant effects of UV-B treatment were observed in biomass accumulation, leaf ontogeny, flowering or productivity.     

Soluble and membrane symbiosis-related polypeptides associated with the development of arbuscular mycorrhizas in tomato (Lycopersicon esculentum)

To analyse the effect of arbuscular mycorrhizal (AM) colonization on tomato gene expression, two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) patterns of crude extracts, soluble and membrane proteins of tomato roots, either mycorrhizal and the AM fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe or non-mycorrhizal, have been compared. In the three fractions analysed, AM colonization induced up-regulation with down-regulation of the synthesis of polypeptides already present in tomato roots and induction of some new polypeptides. Separation of root extracts into soluble and membrane fractions allowed us to identify two soluble, and five membrane-bound, newly induced polypeptides in AM roots. Comparison of the protein patterns of AM roots with those of the external mycelium of G. mosseae showed that one of the newly induced polypeptides might correspond to a fungal polypeptide. By using this experimental approach, we have been able to detect 44 polypeptides that are differentially displayed in tomato roots as a consequence of the establishment of the AM symbiosis.     

Ultrastructure and lipid alterations induced by cadmium in tomato (Lycopersicon esculentum) chloroplast membranes

The effects of cadmium (Cd) uptake on ultrastructure and lipid composition of chloroplasts were investigated in 28-day-old tomato plants (Lycopersicon esculentum var. Ibiza F1) grown for 10 days in the presence of various concentrations of CdCl2. Different growth parameters, lipid and fatty acid composition, lipid peroxidation, and lipoxygenase activity were measured in the leaves in order to assess the involvement of this metal in the generation of oxidative stress. We first observed that the accumulation of Cd increased with external metal concentration, and was considerably higher in roots than in leaves. Cadmium induced a significant inhibition of growth in both plant organs, as well as a reduction in the chlorophyll and carotenoid contents in the leaves. Ultrastructural investigations revealed that cadmium induced disorganization in leaf structure, essentially marked by a lowered mesophyll cell size, reduced intercellular spaces, as well as severe alterations in chloroplast fine structure, which exhibits disturbed shape and dilation of thylakoid membranes. High cadmium concentrations also affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the fatty acid content and a shift in the composition of fatty acids, resulting in a lower degree of fatty acid unsaturation in chloroplast membranes. The level of lipid peroxides and the activity of lipoxygenase were also significantly enhanced at high Cd concentrations. These biochemical and ultrastructural changes suggest that cadmium, through its effects on membrane structure and composition, induces premature senescence of leaves.