Floret Formation Research Articles

Transcriptomic analysis reveals the formation mechanism of anemone-type flower in chrysanthemum

BackgroundThe ray and disc florets on the chrysanthemum capitulum are morphologically diverse and have remarkably abundant variant types, resulting in a rich variety of flower types. An anemone shape with pigmented and elongated disk florets is an important trait in flower shape breeding of chrysanthemums. The regulatory mechanism of their anemone-type disc floret formation was not clear, thus limiting the directional breeding of chrysanthemum flower types. In this study, we used morphological observation, transcriptomic analysis, and gene expression to investigate the morphogenetic processes and regulatory mechanisms of anemone-type chrysanthemum.ResultScanning electron microscopy (SEM) observation showed that morphological differences between non-anemone-type disc florets and anemone-type disc florets occurred mainly during the petal elongation period. The anemone-type disc florets elongated rapidly in the later stages of development. Longitudinal paraffin section analysis revealed that the anemone-type disc florets were formed by a great number of cells in the middle layer of the petals with vigorous division. We investigated the differentially expressed genes (DEGs) using ray and disc florets of two chrysanthemum cultivars, 082 and 068, for RNA-Seq and their expression patterns of non-anemone-type and anemone-type disc florets. The result suggested that the CYCLOIDEA2 (CYC2s), MADS-box genes, and phytohormone signal-related genes appeared significantly different in both types of disc florets and might have important effects on the formation of anemone-type disc florets. In addition, it is noteworthy that the auxin and jasmonate signaling pathways might play a vital role in developing anemone-type disc florets.ConclusionsBased on our findings, we propose a regulatory network for forming non-anemone-type and anemone-type disc florets. The results of this study lead the way to further clarify the mechanism of the anemone-type chrysanthemum formation and lay the foundation for the directive breeding of chrysanthemum petal types.

Whole-transcriptome profiles of Chrysanthemum seticuspe improve genome annotation and shed new light on mRNA–miRNA–lncRNA networks in ray florets and disc florets

BackgroundChrysanthemum seticuspe has emerged as a model plant species of cultivated chrysanthemums, especially for studies involving diploid and self-compatible pure lines (Gojo-0). Its genome was sequenced and assembled into chromosomes. However, the genome annotation of C. seticuspe still needs to be improved to elucidate the complex regulatory networks in this species.ResultsIn addition to the 74,259 mRNAs annotated in the C. seticuspe genome, we identified 18,265 novel mRNAs, 51,425 novel lncRNAs, 501 novel miRNAs and 22,065 novel siRNAs. Two C-class genes and YABBY family genes were highly expressed in disc florets, while B-class genes were highly expressed in ray florets. A WGCNA was performed to identify the hub lncRNAs and mRNAs in ray floret- and disc floret-specific modules, and CDM19, BBX22, HTH, HSP70 and several lncRNAs were identified. ceRNA and lncNAT networks related to flower development were also constructed, and we found a latent functional lncNAT–mRNA combination, LXLOC_026470 and MIF2.ConclusionsThe annotations of mRNAs, lncRNAs and small RNAs in the C. seticuspe genome have been improved. The expression profiles of flower development-related genes, ceRNA networks and lncNAT networks were identified, laying a foundation for elucidating the regulatory mechanisms underlying disc floret and ray floret formation.

Effect of sulphur, zinc and boron on the growth and yield enhancement of sunflower (Helianthus annuus L.)

Oilseed crops grown in different types of soil experience nutrient deficiency, especially sulphur, zinc and boron, which affect crop productivity. To tackle it, nutrient management practices must be streamlined to avoid improper fertilizations and deterioration of soil health. With this background, experimental trials were conducted to study the effect of sulphur, zinc and boron application on the growth, yield components and yield of hybrid sunflower at AyanAthur village, Ariyalur district (TN) during the summer seasons of 2016 and 2017. The experiments were laid out in Randomized Block Design (RBD) with three replications. The growth components of sunflower (plant height, leaf area index, dry matter production, leaf area duration (LAD) and growth analysis parameters such as crop growth rate (CGR), relative growth rate(RGR), net assimilation rate(NAR) and chlorophyll content, yield components and seed yield were significantly (level of significance P>0.05) influenced by foliar application of 0.5% Zn on bud initiation stage and seed formation stage and B @ 0.3% on bud initiation stage and ray floret formation stage along with S(sulphur) @ 40 kg ha-1 and RDF(recommended dose of fertilizers) as a soil application. Growth and yield parameters responded very little with the RDF alone. From both experimental results, we found that foliar application of Zn @ 0.5%and B @ 0.3% along with S @ 40 kg ha-1 and RDF recorded the highest percentage of dry matter production (44.4%), number of filled seeds (30.1%) and yield (32.4%) of hybrid sunflower.

Multifloret spikelet improves rice yield.

The typical rice (Oryza sativa) spikelet contains a single fertile floret and produces only one grain; by contrast, Brachypodium distachyon spikelets contain multiple fertile florets and produce several grains. To increase yield, rice breeders have traditionally focused on panicle morphology (branch number and length, spikelet density), but have not considered the number of florets in each spikelet. Production of rice spikelets with more florets could further increase the number of grains per panicle. Here, we describe two novel approaches - altering meristem determinacy and restoring lateral floret formation - for breeding rice cultivars with a multifloret spikelet, thereby increasing the number of grains per panicle and potentially improving yield.

Grain yield of durum wheat as affected by waterlogging at tillering

Waterlogging is one of the limiting factors influencing durum wheat (Triticum durum L.) production. In this paper we investigated the impact of seven waterlogging durations of 4, 8, 12, 16, 20, 40, and 60 days, imposed at 3-leaf and 4-leaf growth stages, on grain yield, grain yield components, straw and root dry weight and nitrogen concentration of grain, straw, and roots of two varieties of durum wheat. Grain yield of both varieties showed a significant reduction only when waterlogging was prolonged to more than 20 days, and 40-d and 60-d waterlogging reduced grain yield by 19% and 30%. Waterlogging depressed grain yield preventing many culms from producing spikes. It slowed down spikelet formation, consequently reducing the number of spikelets per spike, and reduced floret formation per spikelet, thus reducing the number of kernels per spike.

Waterlogging at tillering affects spike and spikelet formation in wheat

Waterlogging stress is one of the limiting factors influencing wheat (Triticum aestivum L.) production. Wheat tolerance to waterlogging is related to the duration of the waterlogging event, the crop development stage in which waterlogging occurs, and the sensitivity of genotype. In this paper we investigated the impact of eight waterlogging durations (from 0 to 60 days) imposed at 3-leaf and 4-leaf growth stages (~30 and 40 days after sowing) on grain yield, grain yield components, straw and root dry weight and nitrogen concentration of grain, straw, and roots of two cultivars of wheat. The results showed that of the two cultivars, one (cv. Blasco) was tolerant to waterlogging and the other (cv. Aquilante) was sensitive, thus confirming that there are high genotypic differences in terms of tolerance to waterlogging in wheat. The sensitive cultivar showed a significant reduction in grain yield and straw and root dry weight only when waterlogging was prolonged for more than 20 days. Waterlogging depressed the grain yield of the sensitive cultivar, slowing tiller formation and consequently preventing many culms from producing spikes. It slowed down spikelet formation, consequently reducing the number of spikelets per spike, and reduced floret formation per spikelet, thus reducing the number of kernels per spike.

夏秋ギク型輪ギク品種に対する花芽分化・発達期における細霧冷房が開花および小花形成に及ぼす影響

夏秋ギク型輪ギク品種に対する花芽分化・発達期における細霧冷房が開花および小花形成に及ぼす影響

Non-destructive staging of barley reproductive development for molecular analysis based upon external morphology

A prerequisite to study the molecular genetic pathways of pollen and anther development is an accurate staging system for reproductive development. However in barley, floret formation occurs mainly within the pseudostem, which makes the observation of floret development and access to the floret particularly difficult without dissecting the plant. Thus selecting stages for molecular analysis cannot be done non-destructively. A staging method has therefore been developed for barley in order to define the relationship between readily detectable growth points and reproductive development, to provide a clear key to enable accurate selection of reproductive material. Initial staging followed the traditional Zadoks decimal system, with minor adaptations to stages 31–34 and stage 37. The later stages, from 37 onward, were replaced by growth staging based upon the last flag elongation (LFE) and the position occupied by the spike within the pseudostem. Spike size could be readily predicted by using the staging system incorporating Zadoks stages 31–37, supplemented with substages and by LFE staging to improve accuracy. The different spike sizes, as well as the LFE stages, showed a clear relationship to events occurring within the anther, as confirmed by light microscopy of the anthers. The defined relationship between spike size and development to anther development now makes possible the accurate prediction of anther and pollen progression by external staging. This, therefore, provides a mechanism for non-destructive selection of material for analysis that is critical for the molecular characterization of genes in anther and pollen development.

Zm401, a short‐open reading‐frame mRNA or noncoding RNA, is essential for tapetum and microspore development and can regulate the floret formation in maize

In flowering plants, pollen formation depends on the differentiation and interaction of two cell types in the anther: the reproductive cells, called microsporocytes, and somatic cells that form the tapetum. Previously, we cloned a pollen specific gene, zm401, from a cDNA library generated from the mature pollen of Zea mays. Expression of partial cDNA of zm401 in maize and ectopic expression of zm401 in tobacco suggested it may play a role in anther development. Here we present the expression and functional characterization of this pollen specific gene in maize. Zm401 is expressed primarily in the anthers (tapetal cells as well as microspores) in a developmentally regulated manner. That is, it is expressed from floret forming stage, increasing in concentration up to mature pollen. Knockdown of zm401 significantly affected the expression of ZmMADS2, MZm3-3, and ZmC5, critical genes for pollen development; led to aberrant development of the microspore and tapetum, and finally male-sterility. Zm401 possesses highly conserved sequences and evolutionary conserved stable RNA secondary structure in monocotyledon. These data show that zm401 could be one of the key growth regulators in anther development, and functions as a short-open reading-frame mRNA (sORF mRNA) and/or noncoding RNA (ncRNA).

Effects of water-deficit stress on the transcriptomes of developing immature ear and tassel in maize

Water-deficit stress during meiosis is one of the most serious threats to crop production. To elucidate the mechanisms of the response to water-deficit stress in the reproductive organs of maize, we have characterized the changes in transcription that occur during meiosis in the tassels and floret formation in the ears following water deficit stress. We used oligo microarray analysis, which included 57,452 transcripts representing more than 30,000 identifiable unique maize genes, and combined this with reverse Northern blot analysis. After 7 days of stress, immature tassels and ears differed considerably in their transcriptional responses, and the majority of changes were organ specific. In the tassels, 1,513 transcripts were differentially expressed (by threefold or greater) with 62% of these being upregulated by water stress. In the ears, 202 transcripts were differentially expressed with 95% being upregulated by water stress. Most of these transcripts have not been previously reported to be associated with water stress. Only 74 of these transcripts were co-regulated in the two organs. The stress-regulated transcripts are involved in a broad range of cellular and biochemical activities. The most notable may function in carbohydrate metabolism, particular in sucrose, trehalose and raffinose metabolism, and in cell wall metabolism in the tassels. Collectively, these data suggest that the transcripts differentially expressed during reproductive organic development may represent candidate genes for dissecting molecular mechanism of this important biological process in response to water-deficit stress.

Size and Activity of Shoot Apical Meristems as Determinants of Floret Number in Rice Panicles

The sink capacity (floret number per unit land area) is currently a serious constraint to grain yield production in japonica rice. The size and activity of the early reproductive shoot apex (incipient panicle) are potential determinants of the number of florets generated on the panicle. This hypothesis was tested using eight field-grown japonica rice cultivars (IR65598-112-2, IR65564-44-51, Nipponbare, Akenohoshi, Dobashi 1, Koshihikari, Kochihibiki and Nakateshinsenbon). Using morphometric microscopy, we found that the initial size of the reproductive shoot apex was highly correlated with the number of primary branches, but not with the number of florets per primary branch. The cell division activity of the early reproductive apex examined by in situ hybridization analyses using the histone H4 gene probe as a marker for DNA-replicating cells varied with the cultivar. Akenohoshi had twice as many DNA-replicating cells as Nipponbare and the cell division activity was highly correlated with the number of florets per primary branch, but not with the primary branch number. We concluded that the primary branch number was determined by the initial size of the reproductive apex, and that the floret number per primary branch was determined by the cell division activity in the following apex growth. This result provides the first evidence of a relationship between cell division activity and floret formation in the rice panicle.

FRIZZY PANICLE is required to prevent the formation of axillary meristems and to establish floral meristem identity in rice spikelets.

Inflorescences of grass species have a distinct morphology in which florets are grouped in compact branches called spikelets. Although many studies have shown that the molecular and genetic mechanisms that control floret organ formation are conserved between monocots and dicots, little is known about the genetic pathway leading to spikelet formation. In the frizzy panicle (fzp) mutant of rice, the formation of florets is replaced by sequential rounds of branching. Detailed analyses revealed that several rudimentary glumes are formed in each ectopic branch, indicating that meristems acquire spikelet identity. However, instead of proceeding to floret formation, axillary meristems are formed in the axils of rudimentary glumes and they either arrest or develop into branches of higher order. The fzp mutant phenotype suggests that FZP is required to prevent the formation of axillary meristems within the spikelet meristem and permit the subsequent establishment of floral meristem identity. The FZP gene was isolated by transposon tagging. FZP encodes an ERF transcription factor and is the rice ortholog of the maize BD1 gene. Consistent with observations from phenotypic analyses, FZP expression was found to be restricted to the time of rudimentary glumes differentiation in a half-ring domain at the base of which the rudimentary glume primordium emerged.

Categories of resistance at four growth stages in three wheats resistant to the Russian wheat aphid (Homoptera: Aphididae).

Laboratory experiments were conducted to determine categories of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), in three wheats, Triticum aestivum L, (PI 372129, PI 243781, and PI 222668) at Zadoks growth stages 10, 20, 30, and 40. 'TAM 107' was used as the susceptible standard. Antixenosis was observed in PI 222668 and PI 372129. Antibiosis was expressed as reduced nymphipositional period, daily nymph production, and fecundity at the jointing (Zadoks 30) and boot (Zadoks 40) stages in PI 243781 and at tillering (Zadoks 20) in TAM 107. Antibiosis, expressed as reduced intrinsic rate of increase, was observed in PI 222668 at tillering (Zadoks 20). Tolerance to chlorosis and leaf rolling was expressed in the three resistant wheats at all growth stages tested. Tiller production, floret formation, spike length and wet weight were affected by Russian wheat aphid feeding after Zadoks 10. Reduction in spike length did not occur in PI 372129 and PI 243781.

Effect of photoperiods before, during and after vernalization on flower initiation and development and its varietal difference in Japanese bunching onion (Allium fistulosum L.)

SummaryTo control the bolting of Japanese bunching onion (Allium fistulosum L.) photoperiodically, the effect of photoperiods before, during and after vernalization on flower initiation and development and the varietal differences were investigated using the two mid-season flowering cvs Kincho and Asagi-kujo, and a late-season flowering cv. Cho-etsu. A long-day photoperiod (LD, 16 h) given before vernalization inhibited flower initiation. Especially, the bolting rate of ‘Asagi-kujo’ decreased by about a half, compared with the short-day photoperiod (SD, 8 h). The interaction between the effect of night temperature (3°C, 7°C, 11°C or 15°C) and the effect of the photoperiod (SD and LD) during vernalization was also investigated. In ‘Kincho’, LD did not affect flower initiation at 3°C, but inhibited flower initiation at 7°C, 11°C and 15°C. In ‘Asagi-kujo’, flower initiation was significantly inhibited by LD under all temperature conditions. This inhibitory effect was stronger at 11°C and 15°C than at 3°C and 7°C. In ‘Cho- etsu’, LD significantly inhibited flower initiation at 3°C and 7°C, and flower initiation rarely occurred at 11°C and 15°C. In this study, generally, LD during vernalization inhibited flower initiation in all cultivars. Thus Japanese bunching onion required a short-day photoperiod in flower initiation, which was stronger in ‘Asagi-kujo’ and ‘Cho-etsu’ than in ‘Kincho’. From these results, we conclude that low temperature and a short-day photoperiod complementarily induce flower initiation in Japanese bunching onion. Varietal differences exist in the requirement of low temperature and a short-day photoperiod: the primary requirement in ‘Kincho’ is low temperature and that in ‘Asagi-kujo’ is a short-day. After flower initiation, the early stage of flower development is day-neutral, and after the floret formation stage, a long-day photoperiod promotes flower development and elongation of the seedstalk.

Organization of early development by calcium patterns.

This survey focuses on early or primitive developmental phenomena for which the location of a steady high calcium region or the direction of a calcium wave is critical and calcium is more than a trigger. It starts with the long studied roles of calcium in fucoid eggs and in Dictyostelium and progresses to newer work on high calcium regions in medaka fish, zebrafish, and Drosophila eggs. It then proposes that propagated, ultraslow developmental waves in six diverse systems indicate a new and important class of calcium waves. These include the morphogenetic furrow in Drosophila eye discs, floret formation in sunflowers, DNA replication waves in protozoan macronuclei, growth-cone like waves in hippocampal neurons, and two others. It then considers the possible organizing roles of slow calcium waves. Here, it emphasizes surface contractile waves during primary neural induction and elsewhere as well as the possibility of cellular peristalsis. Finally, it reviews the organizing roles of fast calcium waves in ascidian eggs.

Formation of Panicles and Hermaphroditic Florets in Wild-Rice

Formation of panicles and flower primordia in wild-rice, Zizania palustris L., was investigated by scanning electron microscopy (SEM). Floral development involved the formation of both staminate and pistillate floral primordia in the wild-rice spikelet. The SEM study indicated that wild-rice shared a similar developmental process in panicle formation with that of cultivated white rice (Oryza sativa L.). Variations of hermaphroditic floret formation and sex expression were observed in the transition zone between the male and female portions of the panicles in several different wild-rice populations. The frequencies of plants with hermaphroditic floret formation ranged from 27% in the Pistillate population (Z. palustris L.) to 70% in the Peterson Pond (Zizania aquatica L.) population. There was a high degree of phenotypic variation in sex expression in the transition zone of panicles from different wild-rice populations.

Spikelet and floret initiation on tillers of winter triticale and winter wheat in different years and sowing dates

Spikelet and floret initiation on main shoots and the two most developed tillers was studied quantitatively in winter triticale (cv. Grado) and winter wheat (cv. Taras) grown at Rostock. Germany (54.2 °N) from 1985–91 with up to four sowing dates each year. Plants were sampled every 3–10 days between plant emergence and anthesis and the number of primordia were recorded. Floret formation was observed on the tenth spikelet (counting from the base of the ear). Spikelet and floret number were related to thermal time with a base temperature ( T b) of 0°C. The mean and variation in thermal rate and duration of spikelet and floret initiation and spikelet number differed between the cereals but no such differences were observed for maximum or final floret number. Variables varied more in triticale than in wheat. Duration of spikelet and floret initiation varied more than rate of initiation among years, sowing dates and tillers, particularly in triticale. Significant positive relationships between the thermal rate of spikelet and floret initiation and photoperiod were found for triticale and were consistent for all tillers. There was a significant negative relationship between number of spikelet primordia at the time of intersection of the slow and fast rate of primordium initiation and the thermal rate of spikelet initiation for tillers in triticale. Further investigations are needed to describe the effects of temperature, photoperiod and plant development on spikelet and floret initiation. State of application of results about spikelet and floret initiation for simulating grain number was described as low.

シュッコンカスミソウシュートの異なる生育段階における高温遭遇がロゼット化および奇形花発生に及ぼす影響

To determine flowering responses with respect to rosette formation and flower malformation, Gypsophila paniculata L, plants at different developmental stages were exposed to high temperatures after exposure to winter chilling.Initial exposure of vegetative shoots to 30°C from 6:00 to 18:00 and 25°C from 18:00 to 6:00 from 31 Mar. to 10 Apr. resulted in rosette formation in those plants which require long durations of winter chilling such as ‘Perfecta’ and ‘Bristol Fairy’ line 20. Rosette formation occurred even when these plants were grown under optimum conditions. About 50% of the ‘Diamond’ and ‘Bristol Fairy’ line 03 shoots formed rosettes after exposure to 30°/25°C; these cultivars require a relatively lengthy exposure to winter chilling to satisfy their rest requirement. Conversely, ‘Flamingo’, ‘Red Sea’, and ‘Bristol Fairy’ line 08 which require a little chilling did not form rosettes but bloomed.Exposure to high temperature immediately after the onset of flower bud initiation resulted in shorter flower stalks and fewer nodes with inflorescences on the main stem, but no other abnormal morphological changes were observed.Flower malformation was induced when shoots were exposed to high temperature around 30 Apr. when stamen initiation in the terminal floret was occurring. Anatomical studies revealed that the flower malformation was related to an abnormally extended period of transformation of stamens to petaloid structures prior to anthesis. Meristematic activities of the stamen primordia were prolonged after an exposure to high temperature at this stage of floret formation. Consequently, cluster-like petaloid stamens formed around the meristematic tissue that resulted in increased number of petals. Malformed flowers occurred more frequently in cultivars and vegetative lines which require longer durations of chilling.These results show that the exposure to high temperature neutralizes the chilling effects for reproductive growth and induces the formation of rosettes. Both rosettes and malformed flowers may be expressions of the transition from the reproductive growth (anther) to a vegetative one (petal) at the meristematic level, as a result of exposure to high temperature.

Changes in flower bud development ofZinnia elegansJacq. as influenced by the growth retardant S-07

SummaryZinnia elegans treated with S-07((E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol) produced single or half-double flowers, a result of fewer ray florets; this phenomenon was counteracted by GA3 treatment. The developmental changes in flowering induced by S-07 were further observed by scanning electron microscopy (SEM). Treatment of plants with S-07 delayed both the transition from the vegetative to the reproductive stage as well as the reproductive development of the shoot apex by about four days. In the floret formation stage, the petals of the control flowers elongated continuously and remained rounded whereas those of S-07 treated plants became flattened, split into five or six lobes and gradually covered the stamen primordia. The stamen primordia within the base of petals were larger and more well developed following S-07 treatment, compared with the control ones. Further, tubular florets were not formed after S-07 treatment at a late reproductive stage. It is therefore ...

Ontogenic Studies of Shoot Apical Organization in Poinsettia

Summary Shoot apical organization in vegetative and reproductive apices at seven developmental stages was described in Poinsettia (Euphorbia pulcherrima Willd). The vegetative apex showed a tunica-corpus organization with cytohistological zonation. The two layered tunica exhibited lightly stained summital cells. Plastochron depended variations in the number of tunica layers and extent of the CMZ were observed. The inflorescence and floret apices were consumed in cy- athium and floret formation. The inflorescence apex evinced a lighter axial region. The ontogeny of male and female florets was also described. The PZ showed the highest nuclear/cell area ratio throughout the plastochron indicating the highest meristematic activity.