Molecular Regulatory Network of Flowering by Photoperiod and Temperature in Rice

Plants have an ability to flower under optimal seasonal conditions to ensure reproductive success.Photoperiod and temperature are two important season-dependent factors of plant flowering.The floral transition of plants depends on accurate measurement of changes in photoperiod and temperature.Recent advances in molecular biology and genetics on Arabidopsis and rice reveals that the regulation of plant flowering by photoperiod and temperature are involved in a complicated gene network with different regulatory pathways,and new evidence and understanding were provided in the regulation of rice flowering.Here,we summarize and analyze different flowering regulatory pathways in detail in rice based on previous studies and our results,including short-day promotion,long-day suppression,long-day induction of flowering,night break,different light-quality and temperature regulation pathways.     

葡萄成花分子生物学研究进展

开花是植物从营养生长向生殖生长转变的重要时期,而开花调控成为近年来植物分子生物学研究的热点。拟南芥中存在多条调控开花的信号途径如光周期途径、春化途径、赤霉素途径和自主途径等。目前,在葡萄中已经发现了许多葡萄花发育相关的重要基因,是拟南芥花发育相关基因的同源基因,并且绝大多数基因具有与拟南芥相似的功能。本文综述了开花相关基因在葡萄开花时间、花发育过程以及其他过程中的功能,以期为葡萄成花机制的深入研究提供一些参考。     

水稻开花的光温调控分子机理

水稻一生要经历营养生长和生殖生长两个阶段,只有顺利从营养生长向生殖生长转变,水稻才能开花结实。水稻的开花是环境因素与控制水稻开花基因网络相互作用的结果,光照和温度是调控水稻开花的两个重要的环境因子。关于水稻如何感知光照和温度变化,然后启动内部基因的表达来调控水稻开花,科学家提出了一些假说试图解释这个问题。近几年对水稻的开花调控途径的研究有了长足进展,人们对该问题有了新认识。结合前人的研究结果,分析了水稻在不同光温调控下的分子机理。     

Accurate Evaluation of Photoperiodic Sensitivity and Genetic Diversity in Common Buckwheat under a Controlled Environment

Abstract

Photoperiodic sensitivity is one of the most important factors determining whether a crop can adapt to and be cultivated under a broad range of conditions. In common buckwheat (Fagopyrum esculentum Moench), flowering time (flowering of the first flower) is a complex trait influenced by photoperiod, light quality, and temperature, which change daily under natural conditions, and their interaction. Common buckwheat shows a large genetic variation because of the outcrossing reproductive strategy of this species. Thus, flowering time variation within a population reflects both environmental and genotypic variations, and accurate evaluation of photoperiodic sensitivity in common buckwheat requires cultivation under controlled environmental conditions. Here, we investigated photoperiodic sensitivity and its genetic diversity in two buckwheat cultivars, the autumn ecotype Miyazakizairai and the summer ecotype Botansoba, by controlling photoperiod during cultivation under the same temperature regime. Our results showed that (1) the summer ecotype consisted of early-flowering genotypes, including genotypes not found in the autumn ecotype; (2) the autumn ecotype consisted of various genotypes, including early-flowering genotypes and a large number of late-flowering genotypes not found in the summer ecotype; (3) the autumn ecotype showed larger genetic diversity than the summer ecotype in long-day treatments; and (4) genetic diversity first became evident in the 14.5-hr photoperiod in the autumn ecotype, and in the 15.0-hr photoperiod in the summer ecotype. These results support the hypothesis based on previous studies that common buckwheat summer ecotypes were derived from autumn ecotypes by adaptation to climate in northern Japan.     

Water relations and growth of the weed,goosegrass (Eleusine indica), under drought stress

The relative sensitivity to water stress at different growth stages of goosegrass (Eleusine indica (L.) Gaertner) was investigated by measuring water status and growth of groups of plants stressed during the vegetative stage, the reproductive stage, and during both stages. Plants were grown from seed in large pots in a controlled-environment chamber at 29/23°C and 14-h photoperiod. In all treatments, decreasing leaf water-potential was correlated with decreasing osmotic and pressure potentials. Plants stressed during the flowering stage maintained greater pressure potentials at any leaf water-potential than plants stressed during vegetative growth or stressed twice. Prestressing the plants did not induce lower leaf osmotic potentials at full turgor. However, dehydration was the main cause of low osmotic potentials measured in the leaves of the plants stressed twice. Stomatal closure occurred over a relatively large range of leaf water-potentials. The sensitivity of stomata to water stress in this species was fairly similar in the two growth stages studied. Leaves of plants stressed during the flowering stage had a smaller decline in total biomass during the stress period, and a higher rate of growth after rewatering, compared to the plants that received a stress during vegetative growth and flowering or were stressed during vegetative growth.     

Post-flowering photoperiodic effect on reproductive efficiency and seed growth in soybean

Photoperiod not only controls soybean (Glycine max (L.) Merr.) flower induction, but also affects later stages of reproductive growth. Its effect on different yield-determining processes, however, is not well understood. The objective of this work was to determine the post-flowering photoperiodic effect on yield components, reproductive efficiency, and assimilate partitioning to developing seeds in the soybean cultivar Hood 75. Plants were induced to flower in short days. After flowering, three photoperiodic treatments were applied: (1) short days (SD); (2) short days with interrupted night (NI); and (3) a sequential combination of both (NI-SD). Flower differentation, pod lenthening, and seed-filling periods were shortest in SD, intermediate in NI-SD, and longest in NI. The number of differentiated flowers, pods, and seeds were doubled by NI as compared to SD, but the percentages of setting and retained pods were not changed. The percentage of seeds that completed development was, however, increased by SD. More assimilates were partitioned into the seeds in SD, while NI increased the proportion partitioned into shoots. The nitrogen content of seeds was similar in NI and SD, while NI-SD seeds showed a slight increment in their N content. The N content of carpels, however, was high in NI, medium in NI-SD, and low in SD. Compared to NI, duration of the seed-filling period was decreased but the seed-growth rate and final seed size were increased by SD. Final yield was similar for plants in NI or SD, because seed number and seed growth rate compensated each other. Plants in NI-SD has a significantly higher yield, however, as a result of sequential increase in seed number caused by NI, followed by an increase in the rate of seed-filling caused by SD. The results support the existence of two sequential photoperiodic effects on soybean reproductive development: (1), the number of growing seeds is enhanced by NI and decreased by SD; and (2), the assimilate partitioning to seeds is enhanced by SD and decreased by NI. A non-destructive method for seed growth-rate calculation is also described.     

THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON INFLORESCENCE DEVELOPMENT IN STRAINS OF TIMOTHY (PHLEUM SPP.)

A study has been made of the flowering requirements, for temperature and photoperiod, of a range of timothy strains, including American, British and Scandinavian material.
All the strains tested are long-day in their photoperiodic responses, and there is no "winter requirement" for low temperature (0–5°C.) or short days before flowering. There is, however, an inhibitory effect of high temperature in the greenhouse on flower formation, lf the temperature is too high, no heads are produced, although photoperiod may be adequate. Instead elongated indeterminate shoots are formed which often become stoloniferous.
The effect of high temperature varies with the strain, and appears to be related to the May temperature of the region of origin. Under greenhouse temperatures of 55–65°F. American and Canadian commercial strains show little inhibition of flowering, but many plants of the Scandinavian strains fail to produce heads. The British hay strains show intermediate heading behaviour, but only an occasional plant of the diploid S.50 formed heads under these conditions.     

兜兰属植物花期调控研究进展

兜兰由于独特的花朵造型、绚丽的花朵色彩、持久的观赏花期而具有极高的观赏价值,是国际上的高档花卉.但由于生态环境的破坏以及人们对其过度采挖,兜兰现已成为世界上最濒危的植物物种之一,许多种类已濒临灭绝,所有兜兰野生种均被列入《濒危野生动植物种国际贸易公约》(CITES)附录I而被禁止交易.目前,市场上流行的兜兰品种大多是由...     

光周期途径E3泛素连接酶的开花调控机制

开花是植物生长发育过程中非常重要的一个环节,光周期是影响植物开花的主要环境因素。E3泛素连接酶对光周期依赖型的开花起着重要调控作用。已发现的光周期调控开花途径中多种组分均为E3泛素连接酶的靶蛋白,它们能通过E3泛素连接酶介导实现其泛素化降解,从而影响光周期信号,调控开花。综述了E3泛素连接酶在参与调控光受体稳定性、生物钟功能以及开花调控因子CO稳定性三个方面的研究进展。     

Photoperiod regulation of development and growth in bambara groundnut (Vigna subterranea)

The influence of constant photoperiods of 10, 12, 14 and 16 h on development and growth in two bambara groundnut genotypes (Vigna subterranea (L.) Verdc., syn. Voandzeia subterranea (L.) Thouars) was studied in a greenhouse experiment in the Netherlands. Data on dry matter accumulation were collected by sequential harvesting. Photoperiod influenced the onset of flowering in one genotype (‘Ankpa 4’) and the onset of podding in both (‘Tiga Nicuru’ and ‘Ankpa 4’). Under 14- and 16-h photoperiods plants of ‘Ankpa 4’ produced no pods. Photoperiod did not influence total aboveground dry matter production per plant in ‘Ankpa 4’ and had only a slight effect on ‘Tiga Nicuru’. Photoperiod indirectly affected dry matter partitioning via its influence on development: in both genotypes assimilate distribution changed after the photoperiod-induced onset of podding. In addition, a direct influence of photoperiod on partitioning was observed. Firstly, just after the onset of flowering (40 DAS), ‘Tiga Nicuru’ plants under 10- and 12-h photoperiods had accumulated more dry matter as leaf blades and less as stem material than plants under 14- and 16-h photoperiods. Secondly, for ‘Ankpa 4’ the increase in pod dry weight per plant under the 10-h photoperiod was nearly double the increase under the 12-h photoperiod. This difference was associated with a smaller number of developing pods under the 12-h photoperiod. Photoperiod apparently strongly affects the number of developing sinks and, as a consequence, the total sink-strength of the plant, irrespective of the numerous ovaries present on plants of all treatments (including plants of ‘Ankpa 4’ under 14- and 16-h photoperiods).     

茶树成花机理研究进展

开花是植物进入生殖生长的重要标志,花器官的形成在遗传信息传递中起重要作用。茶树是起源于我国西南地区的重要经济作物,具有开花多、花期长的特点。生产上,茶树旺盛的生殖生长会消耗大量营养,影响茶叶的产量和品质。而在杂交育种中,茶树又具有自交不亲和与结实率低等特点。对茶树成花机理的研究有助于深入了解茶树花芽分化和发育的时间、影响因素及分子调控机制,为茶树良种选育、绿色高效生产和育种效率提高等提供理论基础。目前对茶树成花机理的研究已取得一定进展,但还不够深入和系统。本文结合其他植物成花调控最新研究进展,从开花诱导、花芽分化与发育机制方面对茶树开花相关研究取得的进展进行了综述,以期对目前存在的问题和未来研究方向提供有益思考。     

Response of chickpea genotypes to low temperature stress during reproductive development

Low temperature at flowering is a major constraint to improved yield of chickpea in many regions of the world. In particular, cool dryland environments such as southern Australia, parts of the Indian sub-continent and the Mediterranean would benefit from cultivars with the ability to flower and set pods early in the growing season before soil moisture becomes a limiting factor. This paper demonstrates that low temperature (less than 15 °C) affects both the development and function of reproductive structures in the chickpea flower. Aspects of the male and the female gametophyte phases of development are described. Comparisons between chilling sensitive genotypes are made to identify the likely causes of flower abortion. The function of pollen derived from chilling sensitive plants is clearly affected most by low temperature stress, particularly the growth of the pollen tubes down the style before fertilisation occurs. In contrast, pollen tubes derived from chilling tolerant plants continue to grow down the style under low temperature stress. Although other stages of development and function were affected by low temperature, including sporogenesis, pollen germination, and the stigma, none were correlated to the phenotype of the mother plant. The implications of the findings for chickpea improvement programmes are discussed.     

园艺植物花芽分化的研究进展

花芽分化是园艺植物生长发育的重要阶段,是获得优质园艺产品和高产稳产的基础。该文综述了园艺植物花芽分化的形态学特征、植物内源激素水平和光照、温度、水分、矿物质营养等内外因素对花芽分化的影响或调控特征以及园艺植物花芽分化的分子机理,以期为园艺植物的成花管理提供依据。     

竹叶兰花器官发育过程及生理特性研究

本研究通过解剖形态学观察,并检测主要代谢物质、抗氧化酶活性以及内源激素含量的变化,阐述竹叶兰花器官发育特征及生理特性,为新花卉作物的开发利用提供理论依据.结果表明:(1)广州地区户外栽培条件下,竹叶兰全年可开花,为总状花序,单朵次第开花,整枝花期188d;(2)根据花器官发育特征分为5个时期:花芽分化期、萼片伸长期、合...     

The effect of ethylene and abscisic acid on symptom expression of bacterial ring rot in eggplant and potato

Studies were performed to determine the effect that plant hormones involved with plant senescence (i.e., ethylene and abscisic acid) and photoperiod have on disease development and symptom expression of bacterial ring rot (BRR) caused byCorynebacterium sepedonicum (Spieck & Kotth.) Skapt & Burkh. Potato plants were grown either under a long (14 hr.) or short (10 hr.) photoperiod, while eggplants were grown only under a short (10 hr.) photoperiod. Disease severity ratings of BRR were found to be significantly higher (P=0.05) on potato plants grown under a short photoperiod compared to a long photoperiod. Plant heights of BRR infected plants were found to be significantly greater under the long photoperiod. Endogenous levels of ethylene were found to be significantly (P=0.05) greater in inoculated potato plants grown under a long photoperiod than inoculated plants grown under a short photoperiod. Results suggest that the plant hormones ethylene and abscisic acid do not significantly affect the disease development and symptom expression of BRR.     

Contrasting Ppd alleles in wheat: effects on sensitivity to photoperiod in different phases

Photoperiod sensitivity is an important feature of flowering time regulation, which enables wheat plants to adapt to a wide range of environments. Although some work has been done on how time to heading or flowering respond to photoperiod in relation to particular Ppd alleles, there is little evidence on whether these alleles contribute to responses at different phases and to associated yield component generation. The aims of this paper were: (i) to analyse the effects of photoperiod on substitution lines with contrasting Ppd alleles, in terms of duration of particular phases, (ii) to determine if there is any relationship between these alleles and the parameters of photoperiod response (photoperiod sensitivity, optimum photoperiod and basic length of the phase), and (iii) to analyse the effects of different photoperiods applied before and after the onset of terminal spikelet on yield component generation. The effects of length and timing of photoperiod extensions on these traits were analysed under field conditions in Chinese Spring and two substitution lines differing in photoperiod sensitivity.Although time to anthesis was similar in the three genotypes in photoperiods longer than 14.5 h, they did differ in their response to photoperiod in particular phases. Sensitivity to photoperiod for daylengths shorter than 14.5 h was also markedly different. The number of leaves generated was affected by photoperiod, determining the duration of the phase from emergence to floral initiation (EM-FI). The length of the phase from floral initiation to terminal spikelet (FI-TS) was determined by the number of spikelets generated and their rate of initiation, which was also affected by photoperiod. The terminal spikelet to anthesis phase (TS-ANT) was only affected by photoperiod in the most sensitive genotype, in which direct photoperiod effects, other than the effects on leaf number and phyllochron, were evident. There was no apparent relation between photoperiod response parameters such as basic length of the phase (Lb) and optimum photoperiod (Po) and particular Ppd alleles.     

Photoperiodic Regulationof Apical Growth Cessation in Northern Tree Species

Summary

Tree species adapted to the climatic conditions of the northern boreal and subarctic vegetation zones have a capacity to develop a very high level of frost hardiness, even to survive the temperature of liquid nitrogen in midwinter. Proper timing of hardening, as well as of dehardening, is crucial for winter survival of these species. In northern tree species, cessation of apical elongation growth and bud set is a prerequisite for developmental and metabolic processes leading to hardening, and this chain of events is induced by photoperiod. The northern tree species are closely adapted to the local light climate and display photoperiodic ecotypes. The critical photoperiod is under genetic control and increases with increasing latitude of origin of the eco-type. The photoperiod is probably perceived by the phytochrome system, but the role of other pigment systems, like cryptochrome, has not been studied in woody plants. Phytochrome genes have been cloned from both conifers and deciduous species, but so far we do not have any information about possible differences between photoperiodic ecotypes at the phytochrome level. Northern and southern ecotypes have different responses to red:far red ratios, which could indicate differences in composition of their phytochrome systems, for example, the proportions of phytochrome A and B. Both phytochrome A and phytochrome B can be involved in photoperiodic responses. Experiments with transgenic hybrid aspen suggest that responses to photoperiod could be affected by the amount of phytochrome A present in plants. In deciduous species, the plant hormone gibberellin A₁ (GA1) can completely substitute for a long photoperiod, and short day induced cessation of growth is preceded by a significant reduction of GA1 levels, particularly in the elongation zone. Photoperiodic control of GA metabolism is supported by several studies, but very little is known about the interaction between phytochrome and GA metabolism and/or responsiveness to GA1. Although our knowledge is still very fragmentary, available results suggest that cessation of growth and initiation of hardening in trees can be controlled both through the phytochrome and the GA mediated systems. Research with tree species is a tedious and slow process, but with the emerging new methods and approaches, we may expect exciting new results in the near future.     

Incorporating vernalization response functions into an additive phenological model for reanalysis of the flowering data of annual pasture legumes

Vernalization is a physiological process by which plants acquire competence to flower by prolonged exposure to cooling temperatures. A non-linear vernalization module was incorporated into the thermal and photothermal additive models for modelling the time to flowering. The model was applied to published data of time to flowering for annual pasture legumes. Fourteen out of 15 cultivars were detected as vernalization-requiring genotypes. All vernalization-requiring cultivars fitted to the thermal model had R² of below 0.51. After incorporating a vernalization module, the model (vernalizing-thermal model) fitted to nine cultivars with R² of over 0.9. All cultivars were well fitted to the photothermal model with an average R² of 0.94. However, the accountability of variance in observed time to flowering dropped from 94% when the model was tested without cross validation to 68% when the model was tested with cross validation, indicating a poor predictability of the model. Further, the values of parameters for the photothermal model, such as base temperature and coefficients associated with the effect of temperature on the rate of development are unrealistic. The vernalizing-photothermal model not only provided a good fit to the data (averaged R² = 0.98), but it also was able to account for 94% of the variance in the observed data when the model was tested by cross validation. The vernalizing-photothermal model produced meaningful base temperature and the coefficients for the effects of temperature and photoperiod were positive, which are consistent with the suboptimum temperature promotion of flowering and quantitative long day plant behaviour. The vernalizing-thermal model and vernalizing-photothermal model gave an averaged root mean squared error (RMSE) of 3.6 and 2.3 days, compared with the averaged RMSE of 32.4 and 5.9 days for the two respective additive models without the vernalization component. It was concluded that if the vernalization occurs, the additive models without the vernalization module can confound the effects of vernalization that hastens flowering at low temperature with the effects of temperature that promotes flowering at a suboptimum temperature regime. The confounded effects may be forced to be expressed as the unrealistic effects of temperature and base temperature in the model parameters and the model overall has low predictability. The modified additive model that incorporating the vernalization module can be used to quantitatively measure the length of vernalization and is a more valid approach to modelling the time to flowering.