Flower Bud Differentiation Stage Research Articles

Floral Biology of Aquilaria sinensis (Lour.) Spreng

Aquilaria sinensis (Lour.) Spreng is a known medicinal plant producing agarwood. To date, studies on the floral biology of A. sinensis have been limited. In this study, the floral micro- and ultra-structures, pollen viability, stigma receptivity, and artificial pollination of A. sinensis were investigated. The results show that the flower’s development can be divided into five stages, including the flower bud differentiation stage (2–7 d), the flower bud stage (7–13 d), the flowering stage (14 d), the pollination stage (14–15 d), and the fruiting stage (15–25 d). The floral organs mainly include: 4–6 split calyces, 10 petals, 10 stamens, and 1 pistil. The anther is oblong, with four pollen sacs the pollen is round, with maximum viability 6 h after flowering; and stigma receptivity is at its best 6 h before flowering. Artificial pollination is successful in the field. These findings will provide useful information for producing and breeding A. sinensis.

What is going on with the flower bud differentiation and metabolites control of scape elongation on Clivia miniata Regel?

Clivia miniata Regel, a globally renowned ornamental plant, is used in China to celebrate Lunar New Year (the Chinese Spring Festival). However, its anthesis in greenhouses often misses the timing of this festival. Understanding the mechanism of flower bud differentiation and scape elongation is critical for the accurate and stable regulation of anthesis. Currently, little is known about the molecular mechanism of anthesis regulation in C. miniata. In this study, a hypothetical model for its growth and the flowering mechanism was verified by systematic observation over a whole year. Once ripe-to-flower a C. miniata plant followed an autonomous, sympodial, and modular growth system in which the stem apical meristem produced four leaves before terminating in an inflorescence. Paraffin section observation revealed six stages of flower bud differentiation. Moreover, a metabolomic profile of a young leaf adjacent to the scape, at each of four stages of scape development, enabled us to identify metabolites involved in various pathways that correlated with regulation of anthesis. A total of 510 metabolites were identified as present across the different development stages of scapes. Of them, 159 metabolites were differentially expressed, and were enriched in the pathways of amino acid, sugar, glycerophospholipid, and glutathione. Amino acids, sugars, glycerophospholipids, and hormones were suggested to participate in development to anthesis by regulating the molecular network involved in scape elongation. The rate of scape appearance was highest (100 %) following spray application of 50 mg/L GA3. While all treatments could advance anthesis, a spray treatment at 200 mg/L GA3 advanced anthesis by 42 days.

Timing of Floral Differentiation in Four Avocado (Persea Americana Mill.) Cultivars on the Main Island of Okinawa Prefecture, Japan

We conducted a morphological investigation of flower bud differentiation in four cultivars of avocado (Persea americana Mill.): ‘Pinkerton’ (Guatemalan hybrid), ‘Simmons’ (West Indian), ‘Hass’ (predominantly Guatemalan × Mexican), and ‘Monroe’ (Guatemalan × West Indian). The avocado cultivars were planted on the main island of Okinawa Prefecture, which is the only subtropical area of Japan. Buds were collected on 15 November, and 1 and 19 December, 2011, and on 4 and 17 January 2012. The buds were sectioned longitudinally at a thickness of 15 μm through paraffin sectioning, double-stained with Safranin O and Fast green, and observed under an optical microscope to morphologically determine the flower bud differentiation stage. Flower bud differentiation occurred earliest in ‘Pinkerton’ in mid-December, followed by ‘Simmons’ in early January and ‘Hass’ in mid-January. Flower bud differentiation was not observed in ‘Monroe’ during the study period. How to Cite: Takaaki Maeda, Yoshimi Yonemoto, Md. Amzad Hossain, 2023. "Timing of Floral Differentiation in Four Avocado (Persea Americana Mill.) Cultivars on the Main Island of Okinawa Prefecture, Japan." Journal of Agriculture and Crops, vol. 9, pp. 408-412.

Comparative transcriptomic analysis of transcription factors and hormones during flower bud differentiation in ‘Red Globe’ grape under red‒blue light

Grape is a globally significant fruit-bearing crop, and the grape flower bud differentiation essential to fruit production is closely related to light quality. To investigate the regulatory mechanism of grape flower bud differentiation under red‒blue light, the transcriptome and hormone content were determined at four stages of flower bud differentiation. The levels of indole-3-acetic acid (IAA) and abscisic acid (ABA) in grape flower buds at all stages of differentiation under red‒blue light were higher than those in the control. However, the levels of cytokinins (CKs) and gibberellic acid (giberellins, GAs) fluctuated continuously over the course of flower bud differentiation. Moreover, many differentially expressed genes were involved in auxin, CK, GA, and the ABA signal transduction pathways. There were significant differences in the AUX/IAA, SAUR, A-RR, and ABF gene expression levels between the red‒blue light treatment and the control buds, especially in regard to the ABF genes, the expression levels of which were completely different between the two groups. The expression of GBF4 and AI5L2 in the control was always low, while the expression under red‒blue light increased. AI5L7 and AI5L5 expression levels showed an upwards trend in the control plant buds and gradually decreased in red‒blue light treatment plant buds. Through weighted gene coexpression network analysis, we determined that the transcription factors WRK48 (WRKY family), EF110 (ERF family), ABR1, CAMTA3 (CAMTA family), and HSFA3 (HSF family) may be involved in the regulation of the GBF4 gene. This study lays a foundation for further analysis of grape flower bud differentiation regulation under red‒blue light.

The role of phytohormones and their related miRNAs in sex differentiation of Xanthoceras sorbifolium Bunge

• Determined the influence of IAA, GA, ABA, ZT on sex differentiation of Xanthoceras sorbifolium . • Identified 20 significantly differently expressed miRNAs (83 miRNA/target pairs) being related to phytohormone synthesis and signal transduction during sex differentiation. Xanthoceras sorbifolium Bunge is an important woody oilseed tree in north China. However, its yield is severely restricted by a low ratio of female to male flowers, and little is known about the physiological and molecular mechanisms underlying the sex differentiation of flowers. Therefore, carrying out the research in its sex differentiation regulation mechanism is the basis of increasing seed yield. Here, we investigated the cytology of sex differentiation, the content and their ratios of indole-3-acetic acid (IAA), gibberellins (GA 3 ), zeatin (ZT), abscisic acid (ABA), the effects of plant growth regulators on flower development, and the expression profiles of phytohormone-related miRNAs. The results showed that both functional female and male flowers were bisexual at the early stage of flower bud differentiation, while the development of the pistils of male flowers and the stamens of female flowers was arrested at later stage of sex differentiation. Furthermore, IAA, ABA and ZT were shown to be beneficial to pistil development in X. sorbifolium . GA 3 was the key phytohormone in pistil abortion. High level of ABA/ZT was beneficial for microspore mother cell meiosis. ZT/IAA was probably related to pistil abortion. High level of ZT/GA 3 contributed to ovule development. Spraying 6-BA was more effective than GA 3 in increasing female-to-male ratio regardless of CK. In addition, several miRNAs played key roles in sex differentiation, especially miR393, miR396, and miR399. They participated in the regulation of pollen maturation and multiple phytohormone pathways. The present study comprehensively identified the roles of phytohormones and their related miRNAs during sex differentiation in X. sorbifolium , which will be a valuable resource for sex regulation using genetic and physiological methods in the future.

Genome-Wide Characterization of Chrysanthemum indicum Nuclear Factor Y, Subunit C Gene Family Reveals the Roles of CiNF-YCs in Flowering Regulation.

Nuclear Factor Y, Subunit C (NF-YC) transcription factors are conserved in most plants, and play essential roles in plant growth and development, especially in flowering regulation. Chrysanthemums are important commercial plants, and their market value is strongly impacted by flowering time. Until now, no details regarding the NF-YC family in the Chrysanthemum genus have been available. In this study, five NF-YC genes were cloned from Chrysanthemum indicum. Multiple alignments showed that CiNF-YCs had the highly conserved characteristic regions. Phylogenetic analyses identified a pair of paralogue NF-YC proteins in chrysanthemums. Gene structure and conserved motifs were also analyzed for functional understanding. According to the results of the expression experiments, CiNF-YC1 and CiNF-YC5 were mainly expressed in leaves or flowers, and their expression levels varied greatly from the seedling to flower bud differentiation stage. Arabidopsis overexpressing CiNF-YC1 and CiNF-YC3 showed significantly delayed flowering, accompanied by other morphological alterations. RT-qPCR analysis revealed that genes associated with photoperiod, vernalization, aging, and gibberellin pathways were downregulated in CiNF-YC1-OX lines, relative to the wild type, whereas in CiNF-YC3-OX lines, only SHORT VEGETATIVE PHASE (AtSVP), the key factor in the ambient temperature pathway, was upregulated. Taken together, these findings suggest that CiNF-YC1 and CiNF-YC3 negatively regulate flowering in Arabidopsis via different flowering pathways.

Transcriptome Analysis and Differential Gene Screening of Male Flower Buds in Three Age Stages of <i>Ginkgo biloba</i>

In this paper, the key genes of flowering regulation among three age stages was screened and the molecular mechanism of the flowering pathway was revealed in  Ginkgo biloba . It can provide scientific basis for promoting early flowering, molecular breeding and spreading planting of  Ginkgo biloba . High throughput sequencing technology and bioinformatics tools were used to sequence the transcriptome of male flower buds of  Ginkgo biloba  in three age stages. By analyzed the sequencing data, we screened out the key differential expression genes of age pathway. A total of 57.45 Gb of raw data was generated by transcriptome sequencing. The total number of Unigenes was 35 058 and annotated in the 8 functional databases (GO, COG, KEGG, KOG, NR, Pfam, Swiss-Prot, and eggNOG). The Unigenes were classified into 55 GO categories and 126 metabolic pathways. Analysis of differentially expressed genes revealed that 37 genes were up-regulated and 75 genes were down-regulated during the flower bud undifferentiated stage vs. initial stage of flower bud differentiation. A total of 592 genes were up-regulated and 871 genes were down-regulated during the initial stage of flower bud differentiation vs. flower bud differentiation stage. The flower bud undifferentiated stage vs. flower bud differentiation stage，961 genes were up-regulated and 1 203 genes were down-regulated. A large number of flowering related genes were discovered and finally screened out 11 key genes of flowering regulation in age pathway. including  SPL (gene.Gb_23724, gene.Gb_03922),  AP2 (gene.Gb_00766),  MADS-box (gene.Gb_01886, gene.Gb_15398, gene.Gb_28337, Gingko_newGene_2213), Gibberellin-regulated protein(gene.Gb_34467, gene.Gb_28606, gene.Gb_33214)and DELLAs protein(gene.Gb_34644).

Mapping and candidate gene analysis of silique number mutant in <italic>Brassica napus </italic>L.

<p id="C3">The silique number is one of the important components of yield per plant in oilseed rape (<italic>Brassica napus </italic>L.) and the exploitation and utilization of its excellent alleles are essential to increase yield. More than hundreds of silique number QTLs have been mapped in oilseed rape, but they are difficult to be fine-mapped or cloned because of their moderate and unstable effects. A oilseed rape mutant (No.7931) was detected in previous study and it had few siliques at mature stage due to the stop growth after differentiation about 10 flowers on the top of inflorescence. A F₂ segregating population consisting of 3400 individuals was constructed using this mutant and another more-silique lines No.73290. Among them, we performed BSA-seq on 30 individuals with extreme more- or less-siliques and detected three associated intervals of 0-1.1 Mb, 4.7-6.2 Mb, and 11.5-12.4 Mb on the C02 chromosome. These genomic intervals contained a total of 522 annotated genes in the reference genome DarmorV8.1, among which 235 genes had functional annotation and SNP/InDel variation. At the early stage of flower bud differentiation, the shoot apical meristems of two parents were subjected to RNA-seq, and a total of 8958 differentially expressed genes (DEGs) were detected. These DEGs were significantly enriched into 20 pathways, including carbohydrate metabolism, translation, and amino acid metabolism (highly associated with flower bud differentiation) and so on, among which 99 were located in the associated intervals. By the integration of gene functional annotation as well as sequence and expression variation analysis, a total of nine candidate genes (<italic>BnaC02g00490.1D2</italic>,<italic> BnaC02g01030.1D2</italic>,<italic> BnaC02g01120.1D2</italic>,<italic> BnaC02g00270.1D2</italic>,<italic> BnaC02g02670.1D2</italic>,<italic> BnaC02g08680.1D2</italic>,<italic> BnaC02g08890.1D2</italic>,<italic> BnaC02g09480.1D2</italic>, and <italic>BnaC02g10490.1D2</italic>) were identified, which were mainly involved in the maintenance of inflorescence meristems and the regulation of flower development. The above results lay the foundation for the following fine-mapping and cloning of the silique number mutant gene in oilseed rape.

Effects of P fertilizer on female strobilus and needle N and P nutrition of Pinus massoniana clones with different fruiting abilities.

In order to realize precise fertilization and high yield management of Pinus massoniana clonal seed orchard, clones with different fruiting abilities were used as the materials. Four P fertilization levels were at 0, 400, 800 and 1600 g per plant (P0, P4, P8 and P16 respectively). Fertilization was applied before floral primordia formation and after cone picked, respectively. The effects of P fertilizer on the female strobilus of P. massoniana clones and the changes of N, P contents in needles of different positions during floral primordia formation stage and early stage of flower bud differentiation were investigated. The results showed that compared with P0, the female strobilus of P8 and P16 were significantly increased by 67.4% and 61.2% in 2018 and 28.9% and 14.1% in 2019, respectively. There was a significant negative correlation between the female strobilus with the N content and N/P, a significant positive correlation between the female strobilus and the P content in needles. The responses of N and P contents in needles to P fertilization differed in clones with different fruiting abilities. In floral primordia formation stage, the N content of clones with weak fruiting ability was high, and the N/P was 11.5-12.5, while the P content of clones with strong fruiting abilities was high, and the N/P was 9.5-10.5. During this period, the P content of most clones under P8 treatment was the highest, while the N/P was lowest. In the early stage of flower bud differentiation, the N/P of two fruiting clones was 15.3-17.0 and 13.2-15.1, respectively. The P content in upside layer was significantly higher while N/P was significantly lower than that in middle and lower layers. In conclusion, the 800 g P fertilization per plant could increase the P content and reduce the N/P of needles during the floral primordia formation stage of clones with diffe-rent fruiting abilities, which was beneficial to the formation of female strobilus and promote the yield of clone seed orchards.

Identification and cloning of GbMADS6, a SOC1 homolog gene involved in floral development in Ginkgo biloba

Ginkgo biloba is a dioecious plant with a long juvenile stage. With advances in molecular technology, expression verification and functional analysis of some MADS-box family genes have been performed to explore the flowering mechanism in Ginkgo. Here, we selected the gene Gb01884 of different expression from transcriptome sequencing database, and isolated it from the shoot apical meristem (STM) of Ginkgo biloba. Full-length cDNA was cloned and sequence alignment was performed by NCBI platform. The result showed that Gb01884 was designated as an allele gene and named as GbMADS6, a SOC1 homolog gene. Using RT-qPCR to explore the GbMADS6 expression in spatial dynamic, we found that its expression level was high in leaves, apex stems, short shoots of both male and female Ginkgo trees. Then, the expression level of GbMADS6 was measured at the different development stages of leaves and apex stems. In apex stems, the expression level of GbMADS6 increased at initial differentiation stage of flower bud, and decreased gradually along with flower bud development. In leaves, the expression level of GbMADS6 decreased at initial differentiation stage of flower bud, while increased at exuberant stage of flower bud differentiation. This study provides the basis for further understanding the regulation mechanism of flowering in Ginkgo.

High‐resolution temporal dynamic transcriptome landscape reveals a GhCAL‐mediated flowering regulatory pathway in cotton (Gossypium hirsutum L.)

SummaryThe transition from vegetative to reproductive growth is very important for early maturity in cotton. However, the genetic control of this highly dynamic and complex developmental process remains unclear. A high‐resolution tissue‐ and stage‐specific transcriptome profile was generated from six developmental stages using 72 samples of two early‐maturing and two late‐maturing cotton varieties. The results of histological analysis of paraffin sections showed that flower bud differentiation occurred at the third true leaf stage (3TLS) in early‐maturing varieties, but at the fifth true leaf stage (5TLS) in late‐maturing varieties. Using pairwise comparison and weighted gene co‐expression network analysis, 5312 differentially expressed genes were obtained, which were divided into 10 gene co‐expression modules. In the MElightcyan module, 46 candidate genes regulating cotton flower bud differentiation were identified and expressed at the flower bud differentiation stage. A novel key regulatory gene related to flower bud differentiation, GhCAL, was identified in the MElightcyan module. Anti‐GhCAL transgenic cotton plants exhibited late flower bud differentiation and flowering time. GhCAL formed heterodimers with GhAP1‐A04/GhAGL6‐D09 and regulated the expression of GhAP1‐A04 and GhAGL6‐D09. GhAP1‐A04‐ and GhAGL6‐D09‐silenced plants also showed significant late flowering. Finally, we propose a new flowering regulatory pathway mediated by GhCAL. This study elucidated the molecular mechanism of cotton flowering regulation and provides good genetic resources for cotton early‐maturing breeding.

An Integrative Analysis of Transcriptome, Proteome and Hormones Reveals Key Differentially Expressed Genes and Metabolic Pathways Involved in Flower Development in Loquat.

Flower development is a vital developmental process in the life cycle of woody perennials, especially fruit trees. Herein, we used transcriptomic, proteomic, and hormone analyses to investigate the key candidate genes/proteins in loquat (Eriobotrya japonica) at the stages of flower bud differentiation (FBD), floral bud elongation (FBE), and floral anthesis (FA). Comparative transcriptome analysis showed that differentially expressed genes (DEGs) were mainly enriched in metabolic pathways of hormone signal transduction and starch and sucrose metabolism. Importantly, the DEGs of hormone signal transduction were significantly involved in the signaling pathways of auxin, gibberellins (GAs), cytokinin, ethylene, abscisic acid (ABA), jasmonic acid, and salicylic acid. Meanwhile, key floral integrator genes FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) and floral meristem identity genes SQUAMOSA PROMOTER BINDING LIKE (SPL), LEAFY (LFY), APETALA1 (AP1), and AP2 were significantly upregulated at the FBD stage. However, key floral organ identity genes AGAMOUS (AG), AP3, and PISTILLATA (PI) were significantly upregulated at the stages of FBE and FA. Furthermore, transcription factors (TFs) such as bHLH (basic helix-loop-helix), NAC (no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF1/2) and cup-shaped cotyledon (CUC2)), MYB_related (myeloblastosis_related), ERF (ethylene response factor), and C2H2 (cysteine-2/histidine-2) were also significantly differentially expressed. Accordingly, comparative proteomic analysis of differentially accumulated proteins (DAPs) and combined enrichment of DEGs and DAPs showed that starch and sucrose metabolism was also significantly enriched. Concentrations of GA3 and zeatin were high before the FA stage, but ABA concentration remained high at the FA stage. Our results provide abundant sequence resources for clarifying the underlying mechanisms of the flower development in loquat.

Effect of Integral Control of Water and Fertilization on the Content of Mineral Nutrient in Leaves during Flower Bud Differentiation in Apple

Apple is one of the most important fruit crops in the worldwide. Although Drip irrigation fertilization has been widely promoted and applied in agricultural developed countries such as Europe and America, but the ratio, application amount and use period of fertilizers for drip irrigation are not clear in China. Here, taking the traditional fertilization as the control, the effects of different N, P, K application rates on the nutrient elements content and growth of trees were studied under the condition of drip fertilization, in order to clarify the best period and application rate of drip fertilization during flower bud differentiation. We found that the peak of nitrogen demand in late June, and the K, Ca and Zn was related with the early stage of flower bud differentiation. Low Controlling fertilizer was beneficial to regulating branch capping. In short, nitrogen fertilizer needs to be applied before June of apple tree.

The Effects of Endogenous Hormones on the Flowering and Fruiting of Glycyrrhiza uralensis.

Although endogenous hormones play an important role in flower bud differentiation and seed-filling, their effects on the flowering and fruiting of Glycyrrhiza uralensis Fisch. remain unknown. In the present study, we investigate the differences in the levels of endogenous hormones gibberellic acid (GA), abscisic acid (ABA), zeatin riboside (ZR), and indoleacetic acid (IAA) between the fruiting and seedless plants of G. uralensis Fisch. at different growth stages. We also determine the correlations of the endogenous hormone with the rates of flower and fruit falling, rate of empty seeds, rate of shrunken grains, and thousand kernel weight (TKW). The results demonstrate that the IAA and ZR levels of the flowering plants are significantly higher than those of the nonflowering plants at the flower bud differentiation stage. The GA and ABA levels of exfoliated inflorescence plants are considerably higher than those of the flowering and fruiting plants; the rates of falling flowers and fruit are negatively correlated with the IAA level and positively correlated with the ABA level. The ABA content of nonflowering plants is significantly higher than that of fruiting plants. The ZR:GA and IAA:ABA ratios are significantly positively correlated with TKW. The IAA:GA and IAA:ABA ratios are significantly negatively correlated with the rates of empty and shrunken seeds. Thus, we speculate that high IAA and ZR contents are good for flower bud differentiation and seed-filling, and low ABA and ZR contents are beneficial to flower bud development and seed-filling.

Isolation, functional characterization and evolutionary study of LFY1 gene in Prunus mume

The flowering transition is a qualitative change in the life cycle of higher plants and an important turning point in the transition from vegetative to reproductive growth. Despite the significant importance, the molecular regulation mechanism of the flowering transition of mei (Prunus mume) remains poorly defined. In this study, RT-PCR was used to clone a LFY (LEAFY)-like gene in P. mume ‘Changrui Lve’ and functional characterisation of the gene was carried out. The gene showed high homology to the homologous genes of other woody plants, suggesting that PmLFY-like gene exhibits relatively high conservation as flowering-related genes. Expression of PmLFY1 gene in different organs by real-time quantitative PCR showed that this gene was highly expressed in the late stage rather than early stages of flower bud differentiation in P. mume, thereby exhibiting an active regulatory role in flower organ differentiation. Overexpression of LFY1 in Arabidopsis exhibited phenomenal phenotypic changes in transgenic plants, wherein PmLFY-like gene demonstrated the ability to advance the flowering and promoted the transition of inflorescence meristem to floral meristem. Thus, the PmLFY-like gene was not only involved in regulating the duration of flowering and transition to flowering but also played a role during all stages of inflorescence and flower development. These results can be used to conduct a comprehensive and systematic study of the gene functions which can lay the foundation for the molecular research of flowering in mei.

Effect of exogenous GA₃ and DPC on active components of Lonicera japonica and its mechanism

To reveal the effect of plant growth regulator GA₃ and DPC on the active components and its possible mechanism of Lonicera japonica. GA and DPC were applied at the stage of flower bud differentiation, and the content of active ingredients was measured by LC-MS-MS, the content of endogenous hormones were measured by ELISA, and the expression of key enzyme enes expression was determined by qRT-PCR. The level of endogenous hormone GA₃, IAA, ZR, DHZR and iPA in the GA treatment group was significantly improved, the expression of C4H1, C4H2, 4CL1 and HQT2 were also significantly increased. The content of chlorogenic acid, luteolin, luteoloside, isoquercetin and caffeic acid increased significantly. Spraying DPC did not affect or inhibit the accumulation of active components of L. japonica. Spraying GA can increase the content of endogenous GA₃, thus enhance the expression of C4H1, C4H2, 4CL1 and HQT2, and then increase the content of chlorogenic acid and luteolin.

Cloning, sequence, and expression analyses of the Chrysanthemum morifolium flowering-related gene CmCOL (CONSTANS-like)

We cloned the CmCOL gene (GenBank accession: KC589293) from Chrysanthemum morifolium ‘Jinba’. The complete cDNA sequence is 1439 bp in length; the open reading frame is 1161 bp and encodes a polypeptide of 387 amino acids. Analysis of the amino acid sequence shows homology to the protein encoded by the plant flowering gene CO (CONSTANS). CmCOL contains a typical, functional CO domain at the N-terminus, two B box-type zinc finger domains, eight predicted zinc ion binding sites, one CCT(CO, CO-Like, TOC1) domain near the C-terminus and a specific six amino acid consensus sequence (G-I/V-V-P-S/T-F) at the C-terminus, and belongs to CONSTANS family Group I. A protein phylogenetic tree revealed 99% identity between CmCOL and Chrysanthemum seticuspe f. boreale CONSTANS-like1. We predict that CmCOL localizes to the nucleus, is not secreted and lacks a signal peptide. Relative fluorescence quantitative analysis showed that CmCOL mRNA is most highly expressed in the leaves and follows a diurnal expression pattern, with a maximum at 04:00, its lowest point at 16:00 and maintaining this low expression until 20:00. Short-day conditions elevated CmCOL mRNA expression in the leaves but did not significantly affect expression in the buds. The CmCOL mRNA level in the leaves varied significantly based on the flower bud differentiation stage. Further detailed study of this gene will help to elucidate the molecular mechanisms by which the photoperiod pathway regulates chrysanthemum flower formation. Further, this gene may represent a potential, future target for molecular breeding.

Cloning and expression analysis of F3'H and quantification of downstream products in Chrysanthemum morifolium under flooding stress

To investigate the effects of the expression of flavonoid 3' hydroxylase gene (F3'H) and active ingredients in Chrysanthemum morifolium under flooding stress, we cloned F3'H from Hangju (temporarily named CmF3'H) and conducted bioinformatics analysis. During the flower bud differentiation stage, we flooded the Ch. morifolium and then used the Real-time PCR to detect the relative expression of CmF3'H; Finally, active ingredients of the inflorescence were measured by HPLC.The sequencing results showed that 1 562 bp sequence was acquired with the largest open reading frame of 1 527 bp, which encoded 508 amino acids. The phylogenetic tree found that CmF3'H was highly homologous to other species of Compositae. Real-time PCR results showed that CmF3'H had a significant response to flooding stress and had the highest expression level after flooding for 24 h, which was about 9 times as that of the control group. The results of HPLC showed that luteolin and luteoloside, the downstream products catalyzed by the F3'H, were significantly higher than those in the control group. It was also found that the contents of chlorogenic acid and 3,5-O-di-caffeoylquinic acid were also significantly higher than those of the control group. Therefore, Ch. morifolium regulates the synthesis of downstream products by regulating the expression of CmF3'H in the flavonoid synthesis pathway under flooding stress, thereby responding to flooding stress. The flooding stress during flower bud differentiation can significantly enhance the accumulation of active ingredients.

Effects of nitrogen during nursery stage on flower bud differentiation and early harvest after transplanting in strawberry

Flowering is essential for fruit production. The effects of nitrogen (N) on flower bud differentiation and early harvest in strawberry are not clear. Experiments were conducted to investigate the most effective concentration of N treatment during the seedling stage and further elucidate the mechanism of flower bud differentiation in cultivated strawberry (Fragaria ananassa Duch.‘Benihoppe’). The results demonstrated that T2 (treatment 2) of 0.1 g/plant was the suitable concentration for flower bud differentiation in strawberry seedlings and then fruit early ripening. Further studies showed that the period of flower bud differentiation happened between August 19 and August 24. The total carbon (C) contents of all treatments except T3 displayed an increasing trend in seedlings before August 14. The C/N ratio (21.45–53.44) increased at the stage of flower bud differentiation in each treatment, which was promoted by an appropriate C/N ratio. Relatively higher ABA and CTKs levels but relatively lower GAs and IAA levels required during flower bud differentiation were detected. Further analysis of ABA/IAA ratio (0.53–0.76) suggested that it was also close to the flower bud differentiation in strawberry. N levels increased at phenological phases of each treatment. Different N levels during the seedling stage had little effect on fruit quality. It also exhibited the highest early harvest (183.0 g/plant) as well as the highest yield (380.3 g/plant) with T2. We found that a relatively high C/N ratio and an appropriate ABA/IAA positively initiate the flower bud differentiation, which suggested that ABA may play an important role in promoting flower bud differentiation in strawberry.

Cloning and expression analysis of SPL8 homolog from pak choi (Brassica rapa subsp. chinensis)

ABSTRACTSQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) transcription factor genes are functionally diverse; they control a number of fundamental aspects of plant growth and development, including vegetative phase change, flowering time, branching and leaf initiation rate. In our previous study, expression profiling showed that Bra033221, a transcript-derived fragment of an AtSPL8 ortholog, was up-regulated at flower bud differentiation stage 5. This result suggested that Bra033221 has a function similar to that of AtSPL8. In the present study, BrcSPL8, an AtSPL8 homolog, was cloned from pak choi (Brassica rapa subsp. chinensis) based on Bra033221 using reverse transcription-polymerase chain reaction (RT-PCR). The full-length cDNA was 1117 bp and contained a complete open reading frame (ORF) of 987 bp; this ORF encoded a predicted protein with 328 amino acid residues, a calculated molecular mass of 36.55 kDa and an isoelectric point of 8.85. BrcSPL8 was expressed in all analysed apices. Its expression levels before flower differentiation stage 1 were low and almost invariable, and the highest expression was detected in the apex at flower differentiation stage 5, suggesting that BrcSPL8 has a role during flower development in pak choi.