Shoot Inversion-induced Ethylene Production in the Diageotropica Tomato Mutant

Shoot inversion was found to inhibit shoot elongation over 24h in the diageotropica (dgt) mutant tomato and its isogenicparent, VNF8, by 55% and 51%, respectively. Previous studieswith normal tomato and other species would suggest that gravitystress-induced ethylene production in the inverted shoot retardselongation. Since exposure of the diageotropic shoot of thedgt mutant tomato to ethylene restores normal upward growth,it might appear that dgt is defective in its capacity to produceethylene. That shoot inversion did stimulate some ethylene productionand that the ethylene action inhibitor, AgNO₃, largely negatedthe inhibiting effect of shoot inversion on elongation in dgtstrongly suggest that the ethylene produced in the invertedshoot was responsible for its retardation of growth. Althoughethylene production in the slower growing dgt was much lessthan that in the faster-growing VNF8, the dgt shoot was foundto be much more sensitive to ethylene. Shoot inversion, ethylene, shoot elongation, diageotropica (dgt), auxin     

Some Physiological Characteristics of the Ethylene-requiring Tomato Mutant Diageotropica

The diageotropica mutant of tomato (Lycopersicon esculentum Mill.) is shown to require exogenous ethylene for normal growth and development. This single gene mutant is characterized by unsupported horizontal growth of shoots and roots, dark green hyponastic leaf segments, thin rigid stems, and primary and adventitious roots which lack lateral roots. Experiments with growth regulators indicate that the mutant does not produce normal amounts of ethylene in response to auxin treatment. Tests with ethylene-producing compounds or ethylene precursors demonstrate that the mutant requires ethylene for normality. Ethylene concentrations as low as 0.005 microliters per liter are capable of completely normalizing mutant characteristics. This mutant with its isogenic parent variety, cv. VFN8, should be a suitable tool for investigating auxin-stimulated ethylene production and their interrelationship in the control of plant morphology and physiology.     

Ethylene Production and Respiratory Behavior of the rin Tomato Mutant

Little or no change in ethylene or CO₂ production occurred in rin tomato mutant fruits monitored for up to 120 days after harvest. Of the abnormally ripening tomatoes investigated, including “Never ripe” (Nr Y a h, Nr c l₂ r), “Evergreen” (gf r) and “Green Flesh” (gf), only rin did not show a typical climacteric and ethylene rise.     

番茄突变体Epinastics的乙烯反应表现型分析

对番茄(Lycopersicoin esculentum Mil1.)突变体Epinastics(Epi)及其野生亲本VFN幼苗、成长植株和果实生长发育与成熟特性进行了系统研究和比较分析.Epi突变体从幼苗到果实都有乙烯过量合成,在黄化幼苗部分三重反应、成长植株叶柄严重上位生长、器官脱落和果实加速成熟等多方面表现出明显增强的乙烯反应,与已知的乙烯反应模式相符.强烈的顶端优势、紧凑的植株形态提示乙烯在植物的顶端优势调节中可能起着重要的作用.Epi突变体黄化幼苗项勾缩小、叶片和花瓣衰老延迟,与传统的乙烯反应不符,提示植物不同的生长发育特性由不同的乙烯信号转导途径调控.     

番茄果实乙烯释放量的遗传模型分析

本试验选择2个番茄果实乙烯释放量显著不同的番茄品系,通过P_1、P_2、F_1、F_2、B_1和B_2六世代的分析方法,研究了番茄果实乙烯释放量的遗传规律.结果表明:番茄果实乙烯释放量遗传符合1对负向完全显性主基因+加性-显性多基因模型(D-4),主基因效应在B_1、B_2和F_(23)个世代的遗传率分别为36.33%、44.09%和35.14%,多基因效应在B_1、B_2和F_(23)个世代的遗传率分别为54.73%、40.50%和54.88%.     

Biochemical Pathway of Stress-induced Ethylene

Ethylene production from beam and tobacco leaves increased rapidly following the application of toxic compounds such as CuSO₄, Endothal, and ozone. Treatments which increased ethylene evolution also increased the conversion of U-¹⁴C-methionine into ethylene. Cycloheximide inhibited the production of chemical stress-induced ethylene. These results suggest that ethylene is produced by the same biochemical pathway forming basal ethylene, auxin-induced ethylene, or that produced during the ripening of climacteric fruit.     

An Antisense Gene Stimulates Ethylene Hormone Production during Tomato Fruit Ripening

The ripening of many fruits is controlled by an increase in ethylene hormone concentration. E8 is a fruit ripening protein that is related to the enzyme that catalyzes the last step in the ethylene biosynthesis pathway, 1-aminocyclopropane-1-carboxylic (ACC) oxidase. To determine the function of E8, we have transformed tomato plants with an E8 antisense gene. We show here that the antisense gene inhibits the accumulation of E8 protein during ripening. Whereas others have shown that reduction of ACC oxidase results in reduced levels of ethylene biosynthesis, we find that reduction of the related E8 protein produces the opposite effect, an increase in ethylene evolution specifically during the ripening of detached fruit. Thus, E8 has a negative effect on ethylene production in fruit.     

The Diageotropica Gene Differentially Affects Auxin and Cytokinin Responses throughout Development in Tomato

The interactions between the plant hormones auxin and cytokinin throughout plant development are complex, and genetic investigations of the interdependency of auxin and cytokinin signaling have been limited. We have characterized the cytokinin sensitivity of the auxin-resistant diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) in a range of auxin- and cytokinin-regulated responses. Intact, etiolated dgt seedlings showed cross-resistance to cytokinin with respect to root elongation, but cytokinin effects on hypocotyl growth and ethylene synthesis in these seedlings were not impaired by the dgt mutation. Seven-week-old, green wild-type and dgt plants were also equally sensitive to cytokinin with respect to shoot growth and hypocotyl and internode elongation. The effects of cytokinin and the dgt mutation on these processes appeared additive. In tissue culture organ regeneration from dgt hypocotyl explants showed reduced sensitivity to auxin but normal sensitivity to cytokinin, and the effects of cytokinin and the mutation were again additive. However, although callus induction from dgt hypocotyl explants required auxin and cytokinin, dgt calli did not show the typical concentration-dependent stimulation of growth by either auxin or cytokinin observed in wild-type calli. Cross-resistance of the dgt mutant to cytokinin thus was found to be limited to a small subset of auxin- and cytokinin-regulated growth processes affected by the dgt mutation, indicating that auxin and cytokinin regulate plant growth through both shared and separate signaling pathways.     

番茄子时外植体芽的分化过程与乙稀释放的关系

本文对番茄子对外植体培养过程中乙烯的释放和芽的分化进行了研究。结果表明,番茄子对外植体培养１ｈ后开始释放乙烯,第３小时乙烯释放达到最高峰,随后迅速下降,乙烯释放水平与番茄子对外植体分化能力呈负相关。外植体芽的分化过程中,乙烯释放水平很低,但在芽形成以前略有增加,乙烯拮抗剂及其生物合成抑制剂促进子对外植体芽的分化过程。伤害可能是导致番茄子叶外植体乙烯释放的主要原因。     

Ethylene and 1 -Aminocyclopropane-1-Carboxylic Acid Production in flacca, a Wilty Mutant of Tomato, Subjected to Water Deficiency and Pre-treatment with Abscisic Acid

Neill, S. J., McGaw, B. A. and Horgan, R. 1986. Ethylene and1-aminocyclopropane-l-carboxylic acid production in flacca,a wilty mutant of tomato, subjected to water deficiency andpretreatment with abscisic acid —J. exp. Bot. 37: 535–541. Plants of Lycoperstcon esculentum Mill. cv. Ailsa Craig wildtype and flacca (flc) were sprayed daily with H²O or 2?10^–2mol m^–3 abscisic acid (ABA). ABA treatment effected apartial phenotypic reversion of flc shoots; leaf areas wereincreased and transpiration rates decreased. Leaf expansionof wild type shoots was inhibited by ABA. Indoleacetic acid (IAA), ABA and l-aminocyclopropane-l-carboxylicacid (ACC) concentrations were determined by combined gas chromatography-massspectrometry using deuterium-labelled internal standards ABAtreatment for 30 d resulted in greatly elevated internal ABAlevels, increasing from 1?0 to 4?3 and from 0?45 to 4?9 nmolg^–1 fr. wt. in wild type and flc leaves respectively.Endogenous IAA and ACC concentrations were much lower than thoseof ABA. IAA content ranged from 0?05 to 0?1 nmol g^–1 andACC content from 0?07 to 0?24 nmol g^–1 Ethylene emanationrates were similar for wild type and flc shoots. Wilting of detached leaves induced a substantial increase inethylene and ACC accumulation in all plants, regardless of treatmentor type. Ethylene and ACC levels were no greater in flc leavescompared to the wild type. ABA pretreatment did not preventthe wilting-induced increase in ACC and ethylene synthesis. Key words: ABA, ACC, ethylene, wilting, wilty mutants     

Characterization of an Ethylene Overproducing Mutant of Tomato (Lycopersicon esculentum Mill. Cultivar VFN8)

Ethylene production rates and tissue ethylene concentrations were determined for the single-gene, Epinastic (Epi) tomato (Lycopersicon esculentum Mill.) mutant, and its parent, cv VFN8. The Epi phenotype was characterized by severe leaf epinasty, thickened stems and petioles, and a compact growth habit. In 4-day-old seedlings, ethylene production was significantly higher in Epi than in VFN8. Ethylene production rates also were higher for excised root, hypocotyl, cotyledon, and shoot tissue of 14-day-old Epi seedlings as compared with VFN8. The greatest difference in the ethylene production rate was observed in excised Epi shoot tissue, which was more than 2.5 times higher than in VFN8. Tissue ethylene concentrations of 19−, 25−, and 31-day-old Epi plants were 8, 172, and 307% higher than for VFN8, corresponding to increasing expression of the Epi phenotypic characteristics with age. The highest ethylene concentrations occurred in the shoot apex of both genotypes. Higher ethylene concentrations in Epi resulted from greater 1-aminocyclopropane-1-carboxylic acid content rather than increased ethylene-forming enzyme activity. The elevated ethylene levels in Epi did not result from increased auxin sensitivity. The sensitivity of root growth to inhibition by ethylene did not differ between VFN8 and Epi. Although elevated levels of ethylene in Epi plants apparently exacerbate its epinastic growth characteristics, other evidence indicates that this may not be the fundamental lesion. This mutant may provide a unique system for investigating the regulation of ethylene biosynthesis and the role of target cell types in plant development.     

Auxin Physiology of the Tomato Mutant diageotropica

The tomato (Lycopersicon esculentum, Mill.) mutant diageotropica (dgt) exhibits biochemical, physiological, and morphological abnormalities that suggest the mutation may have affected a primary site of auxin perception or action. We have compared two aspects of the auxin physiology of dgt and wild-type (VFN8) seedlings: auxin transport and cellular growth parameters. The rates of basipetal indole-3-acetic acid (IAA) polar transport are identical in hypocotyl sections of the two genotypes, but dgt sections have a slightly greater capacity for IAA transport. 2,3,5-Triiodobenzoic acid and ethylene reduce transport in both mutant and wild-type sections. The kinetics of auxin uptake into VFN8 and dgt sections are nearly identical. These results make it unlikely that an altered IAA efflux carrier or IAA uptake symport are responsible for the pleiotropic effects resulting from the dgt mutation. The lack of auxin-induced cell elongation in dgt plants is not due to insufficient turgor, as the osmotic potential of dgt cell sap is less (more negative) than that of VFN8. An auxin-induced increase in wall extensibility, as measured by the Instron technique, only occurs in the VFN8 plants. These data suggest dgt hypocotyls suffer a defect in the sequence of events culminating in auxin-induced cell wall loosening.     

番茄成熟过程中果皮细胞核孔变化及其与乙烯生成的关系

应用冰冻蚀刻技术探讨了番茄(Lycopersiconesculentum Mill 大红品种)成熟过程中果皮细胞核孔的变化。成熟开始发动时(发白期前,IEC>0.1 ppm)核孔就开始扩大,起初核孔扩大比IEC增加更快,转包期(IEC约10 ppm)达到最大,以后不再变化。核孔扩大先于ACC含量增加。核孔的数量从转色期增加,粉红期最大,成熟后又减少。     

番茄果实成熟过程中钙调素含量变化及其与乙烯生成的关系

应用酶联免疫吸附法(ELISA)测定番茄(Lycopersicon esculentum Mill大红品种)果实成熟过程中钙调素(CaM)含量的变化。果实开始成熟(发白期),CaM含量随着呼吸跃变上升,成熟时(粉红期)达到最大,过熟衰老时则下降。果实内部乙烯浓度、ACC含量及其合成酶活性也随跃变而增加,随过熟衰老而降低。GaM含量在果实不同部位中的分布有明显差异,跃变上升期以子房腔组织含量最高,并由中心向外逐渐降低,外周果皮含量最低。此时用外源乙烯催熟处理促进各部位CaM增加。成熟衰老时子房腔组织首先衰老,CaM含量大为降低,但在中柱和果皮中却高于跃变上升期。外源乙烯促进衰老使CaM下降。Ca~(2+)促进番茄圆片CaM含量增高和乙烯产生,CaM抑制剂CPZ,TFP在降低CaM含量的同时也抑制乙烯的产生。     

Effect of Waterlogged Soil Conditions on the Production of Ethylene and on Water Relationships in Tomato Plants

The roots of tomato plants (Lycopersicon esculentum Mill., cv.Moneymaker) were exposed to low concentrations of oxygen bywaterlogging the soil or by growing the plants in nutrient solutionflushed with nitrogen gas. After 24 h, the rate of ethyleneproduction by the petioles, main stem, and shoot apex was increasedby 4–6-fold and the petioles developed epinastic curvatures.Removing the roots did not reproduce these responses. The amountsof ethylene produced by shoot tissues in response to physicalwounding was greatly increased by waterlogging the soil. The production of ethylene by roots was suppressed by the absenceof oxygen. When the roots were transferred back to an aerobicenvironment ethylene production quickly exceeded that observedin roots maintained continuously in aerobic conditions. The enhanced rate of ethylene production in the shoots occurredin the absence of increased water stress as measured with aleaf pressure chamber; leaf water potentials were increasedrather than decreased by waterlogging for 30 h or more. Thiswas associated with stomatal closure and reduced transpiration.Resistance to water flow through the plant increased as transpirationdecreased in response to waterlogging. However, at similar ratesof transpiration, resistance was normally lower in waterloggedplants than in controls.     

Characterization of the Stimulation of Ethylene Production by Galactose in Tomato (Lycopersicon esculentum Mill.) Fruit

We have characterized the stimulation of ethylene production by galactose in tomatoes (Lycopersicon esculentum Mill.). The effect of concentration was studied by infiltrating 0, 4, 40, 100, 200, 400, or 800 micrograms galactose for each gram of fresh fruit weight into mature green `Rutgers' fruit. Both 400 and 800 micrograms per gram fresh weight consistently stimulated a transient increase in ethylene approximately 25 hours after infiltration; the lower concentrations did not. Carbon dioxide evolution of fruit infiltrated with 400 to 800 micrograms per gram fresh weight was greater than that of lower concentrations. The ripening mutants, rin and nor, also showed the transient increase in ethylene and elevated CO₂ evolution by 400 micrograms per gram fresh weight galactose. 1-Aminocyclopropane-1-carboxylic acid (ACC) content and ACC-synthase activity increased concurrently with ethylene production. However, galactose did not stimulate ACC-synthase activity in vitro. The infiltrated galactose in pericarp tissue was rapidly metabolized, decreasing to endogenous levels within 50 hours. Infiltrated galacturonic acid, dulcitol, and mannose stimulated transient increases in ethylene production similar to that of galactose. The following sugars produced no response: sucrose, fructose, glucose, rhamnose, arabinose, xylose, raffinose, lactose, and sorbitol.     

Ethylene Production,Peroxidase Activity and the Change of Peroxidase Isozyme during the Ripening of Tomato Fruits

Climacteric rise, ethylene production, peroxidase activity and its isozyme and their interrelationships during the ripening of tomato fruits have been studied. It was found' that there was parallelism between ethylene production and climacteric rise. The climacteric rise of tomato fruits was hastened by ethylene applied at the mature green stage. The ethylene production was inhibited by low oxygen and high carbon dioxide partial pressure. The peroxidase activity in the tomato fruits appeared to be different at three stages, higher in the half red fruits and lower in both green mature and fully red fruits. This activity was increased by ethylene and decreased by lower partial pres- sure of oxygen. The peroxidase isozymes sppeared also different at different stages of ripening. There were 4 bands in young fruits, 3 in green mature fruits, 5 in half red fruits and 3 in fully red fruits. After the application of ethylene to the tomato fruits, there appear one new band of peroxidase isozyme.     

番茄果实中乙烯与多聚半乳糖醛酸酶的关系

乙烯与多聚半乳糖醛酸酶(PG)都是果实成熟过程中关键的调节因子.一方面,在有乙烯合成缺陷的转反义ACS番茄和乙烯感受缺陷的Nr突变体番茄果实中PG基因表达量都明显下降,PG酶活性明显降低;用外源乙烯(100 μL/L)处理绿熟期番茄果实使PG基因的表达明显增强,而1-甲基环丙烯(1-MCP,1 μL/L)处理转色期番茄果实明显抑制PG基因表达.另一方面,转反义PG基因番茄果实乙烯释放量在授粉后低于其野生型,番茄乙烯受体基因LeETR4和乙烯反应因子LeERF2基因表达量比野生种低.PG降解果胶的产物D-GA(100 mg/L)促进未熟期番茄果实中的乙烯生成和LeETR4、LeERF2基因的表达.