Normal Flowers Research Articles

Source parameters of the 2016 Menyuan earthquake in the northeastern Tibetan Plateau determined from regional seismic waveforms and InSAR measurements

On January 21st, 2016, a Ms 6.4 earthquake hit Menyuan County, Qinghai province, China. The nearest known fault is the Leng Long Ling (LLL) fault which is located approximately 7 km north of the epicenter. This fault has mainly shown sinistral strike-slip movement since the late Quaternary Period. However, the focal mechanism indicates that it is a thrust earthquake, which is different from the well-known strike-slip feature of the LLL fault. In this study, we determined the focal mechanism and primary nodal plane through multi-step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the China Digital Seismic Network (CDSN). Our results show that the rupture duration was short, within 0–2 s after the earthquake, and the rupture expanded upwards along the fault plane. Based on these fault parameters, we then solve for variable slip distribution on the fault plane using the InSAR data. We applied a three-segment fault model to simulate the arc-shaped structure of the northern LLL fault, and obtained a detailed slip distribution on the fault plane. The inversion results show that the maximum slip is 0.43 m, and the average slip angle is 78.8°, with a magnitude of Mw 6.0 and a focal depth of 9.38 km. With the geological structure and the inversion results taken into consideration, it can be suggested that this earthquake was caused by the arc-shaped secondary fault located at the north side of the LLL fault. The secondary fault, together with the LLL fault, forms a normal flower structure. The main LLL fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block. Therefore, we infer that this earthquake is the manifestation of a neotectonics movement, in which the bulging fault block is lifted further up under the compresso-shear action caused by the Tibetan Plateau pushing towards the northwest direction.

Development of technologies to extend the durian production period

To find alternative procedures for off-season durian production to extend the marketable period, methods of durian flower induction were researched in an experimental field at Chanthaburi Horticultural Research Center during producing years 2010-2013. The applied methods included induction of early flowering using 1) 1000 ppm paclobutrazol, 2) 1000 ppm mepiquat chloride and 3) foliar spray of 1000 ppm chlorate in the first year followed by 2.5 g L-1 0‑42-56 fertilizer in the second year. For induction of late flowering, the following treatments were applied: 4) applying 16-16-16 fertilizer in the dry period, continued watering over the in-season flowering period until physiological mature leaves were produced, which were foliar-sprayed with 1000 ppm PBZ, to induce flowering about 30 days after normal in-season flowering, compared with 5) normal in-season flowering (control). The results revealed that, with the application of 1000 ppm paclobutrazol, all treated trees flowered approximately 9-36 days earlier than the normal in-season flowering, with larger numbers of flowers (7808 flowers tree-1), fruit (31 fruits tree-1), yield (108.59 kg tree-1) and fruit weight (3.60 kg fruit-1). The control treatment had 4614 flowers tree-1, 26 fruits tree-1, 93.43 kg fruit tree-1 and fruit weight 3.86 kg fruit-1. The late flowering method delayed flowering by 28-43 days after the normal in-season flowering. These results indicated that the durian marketable period could be extended by 9-36 days earlier and 28-43 days later than the normal regular time of bearing by using these alternate flower induction methods.

Comparative transcriptomic analyses of normal and malformed flowers in sugar apple (Annona squamosa L.) to identify the differential expressed genes between normal and malformed flowers

BackgroundSugar apple (Annona squamosa L.), a popular fruit with high medicinal and nutritional properties, is widely cultivated in tropical South Asia and America. The malformed flower is a major cause for a reduction in production of sugar apple. However, little information is available on the differences between normal and malformed flowers of sugar apple.ResultsTo gain a comprehensive perspective on the differences between normal and malformed flowers of sugar apple, cDNA libraries from normal and malformation flowers were prepared independently for Illumina sequencing. The data generated a total of 70,189,896 reads that were integrated and assembled into 55,097 unigenes with a mean length of 783 bp. A large number of differentially expressed genes (DEGs) were identified. Among these DEGs, 701 flower development-associated transcript factor encoding genes were included. Furthermore, a large number of flowering- and hormone-related DEGs were also identified, and most of these genes were down-regulated expressed in the malformation flowers. The expression levels of 15 selected genes were validated using quantitative-PCR. The contents of several endogenous hormones were measured. The malformed flowers displayed lower endogenous hormone levels compared to the normal flowers.ConclusionsThe expression data as well as hormone levels in our study will serve as a comprehensive resource for investigating the regulation mechanism involved in floral organ development in sugar apple.

Temporal–spatial patterns of ABCDE model genes expressed in new flowers that emerge from the centres of existing flowers in Chinese cabbage

ABSTRACTWe examined the formation of flower buds and floral organs at five growth stages and compared between normal flowers and those that emerged from the centre of another flower (i.e. flowers-in-flower). Gene expression was analysed via qRT-PCR. When compared with normal flowers, expression of nine genes at corresponding time periods showed clearly different trends in the flowers-in-flower samples, depending upon whether those abnormal structures were of the first types (1–1 and 1–2) or the second types (2–1 and 2–2). For example, at each time point, expression of AP2, STK and SHP was notably higher in 2–1 flowers than in either 1–1 or 1–2 flowers. By contrast, AG expression was up-regulated more between Stages 4 and 5 for normal flowers than for the other types. Furthermore, when compared with normal floral organs, AP1 transcripts were barely detected in the stamens and pistils of mutant samples, and expression was lower in the flowers-in-flower sepals and petals. Except for 2–2 flowers at Stage 5, STK and SHP expression was higher in the mutant organs than in the normal organs. These results suggest that formation of the flowers-in-flower morphology is closely related to down-regulation of AP1 and AG and up-regulation of AP2, STK, and SHP.

Expression Analyses of ABCDE Model Genes and Changes in Levels of Endogenous Hormones in Chinese Cabbage Exhibiting Petal-Loss

Abnormal formation of floral organs affects plant reproduction and can directly interfere with the progress of breeding programs. Using PCR amplification, ABCDE model genes BraAP2, BraAP3, BraPI, BraAG, BraSHP, and BraSEP were isolated from Chinese cabbage (Brassica rapa L. ssp. pekinensis). We examined six development stages of floral buds collected from Chinese cabbage and compared between a line demonstrating normal flowering (A-8) and two mutated lines that exhibited plants having petal-loss (A-16 and A-17). The expression of ABCDE model genes has been analyzed by qRT-PCR. Compared with flower buds of petal-loss plants and normal plants, the expression of A-class gene BraAP2 was significantly decreased during the first to fourth stages, C-class gene BraAG expression was significantly decreased during the first to fifth stages, and D-class gene BraSHP expression was significantly decreased during the first to third stages. Furthermore, B-class gene BraAP3 and BraPI and E-class gene BraSEP expressions were significantly decreased during all six stages of petal-loss plants compared with normal plants. Enzyme-linked immunosorbent assays detected nine endogenous phytohormones during all stages examined here. Except for the second-stage and third-stage buds, levels of the auxin IAA and cytokinin dhZR were always higher in the petal-loss plants than the normal plants at corresponding time points. Meanwhile, concentrations of GA1+3 at the first, fourth, and fifth stages were higher in the petal-loss plants than in the normal plants. Our results provide a theoretical basis for future exploration of the molecular mechanism that determines petal loss and the effects that hormones have on such development in Chinese cabbage plants.

Isolation and functional characterization of a circadian-regulated CONSTANS homolog (GbCO) from Ginkgo biloba.

This is the first report to clone and functionally characterize a flowering time gene GbCO in perennial gymnosperm Ginkgo biloba. GbCO complements the co mutant of Arabidopsis, restoring normal early flowering. CONSTANS (CO) is a central regulator of photoperiod pathway, which channels inputs from light, day length, and circadian clock to promote the floral transition. In order to understand the role of CO in gymnosperm Ginkgo biloba, which has a long juvenile phase (15-20years), a CO homolog (GbCO) was isolated and characterized from G. biloba. GbCO encodes a 1741-bp gene with a predicted protein of 400 amino acids with two zinc finger domains (B-box I and B-box II) and a CCT domain. Phylogenic analysis classified GbCO into the group 1a clade of CO families in accordance with the grouping scheme for Arabidopsis CO (AtCO). Southern blot analysis indicated that GbCO belongs to a multigene family in G. biloba. Real-time PCR analysis showed that GbCO was expressed in aerial parts of Ginkgo, with the highest transcript level of GbCO being observed in shoot apexes. GbCO transcript level exhibited a strong diurnal rhythm under flowering-inductive long days and peaked during early morning, suggesting that GbCO is tightly coupled to the floral inductive long-day signal. In addition, an increasing trend of GbCO transcript level was observed both in shoot tips and leaves as the shoot growth under long-day condition, whereas GbCO transcript level decreased in both tissues under short-day condition prior to growth cessation of shoot in G. biloba. GbCO complemented the Arabidopsis co-2 mutant, restoring normal early flowering. All the evidence being taken together, our findings suggested that GbCO served as a potential inducer of flowering in G. biloba.

SVP-like MADS Box Genes Control Dormancy and Budbreak in Apple.

The annual growth cycle of trees is the result of seasonal cues. The onset of winter triggers an endodormant state preventing bud growth and, once a chilling requirement is satisfied, these buds enter an ecodormant state and resume growing. MADS-box genes with similarity to Arabidopsis SHORT VEGETATIVE PHASE (SVP) [the SVP-like and DORMANCY ASSOCIATED MADS-BOX (DAM) genes] have been implicated in regulating flowering and growth-dormancy cycles in perennials. Here, we identified and characterized three DAM-like (MdDAMs) and two SHORT VEGETATIVE PHASE-like (MdSVPs) genes from apple (Malus × domestica ‘Royal Gala’). The expression of MdDAMa and MdDAMc indicated they may play a role in triggering autumn growth cessation. In contrast, the expression of MdDAMb, MdSVPa and MdSVPb suggested a role in maintaining bud dormancy. Consistent with this, ectopic expression of MdDAMb and MdSVPa in ‘Royal Gala’ apple plants resulted in delayed budbreak and architecture change due to constrained lateral shoot outgrowth, but normal flower and fruit development. The association of MdSVPa and MdSVPb expression with floral bud development in the low fruiting ‘Off’ trees of a biennial bearing cultivar ‘Sciros’ suggested the SVP genes might also play a role in floral meristem identity.

Temporal Petal Closure Benefits Reproductive Development of Magnolia denudata (Magnoliaceae) in Early Spring.

The Magnoliaceae shows strong phylogenetic niche conservatism, in which temporal petal closure has been extensively reported. However, it is yet elusive whether temporal petal closure is an idle floral character inherited from their ancestors or an adaptive trait to their habitats. Here, we monitored the process of temporal floral closure and re-opening in a thermogenic plant, Magnolia denudata (Magnoliaceae). Furthermore, we artificially interrupted temporal petal closure and investigated its effects on development of female and male gametophytes. Intriguingly, we found considerable anatomical changes in the anthers shortly after temporal closure of petals: disintegration of tapeta, crack of anther walls, and release of matured pollens. In comparison with normal flowers, artificially interrupted flowers (no petal closure) showed delayed anther development and slower pollen germination on stigmas, while little difference in embryo morphology was observed during the early stage of embryo development. Moreover, seed set and quality were significantly decreased when petal closure was prevented. In addition, we found pollination accelerated floral closure in M. denudata. Taken together, temporal floral closure benefits reproduction of M. denudata in early spring by promoting anther development and pollen function, which suggests that it is an adaptive floral trait to its specific habitat.

Functional characterization of a novel Brassica LEAFY homolog from Indian mustard: Expression pattern and gain-of-function studies

LEAFY plays a central role in regulation of flowering time and floral meristem identity in plants. Unfortunately, LFY function remains uncharacterized in agronomicaly important Brassicas. Herein, we illustrate fine-mapping of expression domains of LFY in 15 cultivars of 6 Brassica species and describe gain-of-function phenotypes in Arabidopsis and Brassica. We depict early flowering and altered fatty-acid composition in transgenic seed. The cDNA encoding BjuLFY (417aa) shared only 85% identity with reported homolog of B.juncea implying distinctness. Quantitative RT-PCR based coarse expression mapping of BjuLFY in tissue samples representing 3 time points at specific days after sowing (DAS), pre-flowering (30 DAS), flowering (75 DAS) and post-flowering (110 DAS), depicted an intense pulse of BjuLFY expression restricted to primary floral buds (75 DAS) which subsided in secondary floral buds (110 DAS); expression in root samples was also recorded implying neo-functionalization. Fine-mapping of expression during flowering confirmed tightly regulated LFY expression during early stages of bud development in 15 cultivars of 6 Brassica species implying functional conservation. Ectopic expression of BjuLFY in A. thaliana and B. juncea caused floral meristem defects and precocious flowering. B. juncea transgenics (T1) over-expressing BjuLFY flowered 20days earlier produced normal flowers. GC–MS analysis of mature seed from Brassica transgenics showed an altered fatty-acid profile suggestive of seed maturation occurring at lower temperatures vis-à-vis control. Our findings implicate BjuLFY as a regulator of flowering in B. juncea and suggest its application in developing climate resilient crops.

Endoreduplication and gene expression in somaclonal variants of clonally propagated Phalaenopsis ‘Wedding Promenade’

In the current study, we studied somaclonal variants of Phalaenopsis ‘Wedding Promenade’ (WP) to identify the factors that determine variation in this ornamental orchid. We grouped somaclonal variants of Phalaenopsis ‘Wedding Promenade’ based on their flower morphology (WP-N, WP-V1, WP-V2, and WP-V3). Morphological characteristics and histological studies were conducted in addition to flow cytometry and gene expression analyses of the flowers, leaves, and flower stalks. Morphological changes were observed in all WP groups; particularly, the width of the flower and the thickness of each organ were significantly increased when compared with those of normal flowers. The ploidy level of WP-V2 and WP-V3 was doubled in all organs, resulting in hexaploidy, while WP-N and WP-V1 were triploids. A high level of endoreduplication (3C-48C) was detected in the petals, leaves, and flower stalks of the WP Phalaenopsis variants. The expression patterns of HIGH PLOIDY 2 (HPY2) and MADS box transcription factor (PMADS4) isolated from Phalaenopsis were analyzed by real time quantitative PCR. HPY2 expression was the highest in the leaves of WP-V1, whereas its expression in flowers was similar in WP-V1 and normal flowers. Among the various flower organs analyzed, HPY2 expression was the highest in petals and lips of WP-V2. PMADS4 expression was not affected in the floral organs of the Phalaenopsis WP variants. The data identify a simple way to detect somaclonal variation in the Phalaenopsis WP variants and also provide insight into the causes of these variations.

Phosphorylation of SPT5 by CDKD;2 Is Required for VIP5 Recruitment and Normal Flowering in Arabidopsis thaliana.

The elongation factor suppressor of Ty 5 homolog (Spt5) is a regulator of transcription and histone methylation. In humans, phosphorylation of SPT5 by P-TEFb, a protein kinase composed of Cyclin-dependent kinase 9 (CDK9) and cyclin T, interacts with the RNA polymerase II-associated factor1 (PAF1) complex. However, the mechanism of SPT5 phosphorylation is not well understood in plants. Here, we examine the function of SPT5 in Arabidopsis thaliana and find that spt5 mutant flowers early under long-day and short-day conditions. SPT5 interacts with the CDK-activating kinase 4 (CAK4; CDKD;2) and is specifically phosphorylated by CDKD;2 at threonines. The phosphorylated SPT5 binds VERNALIZATION INDEPENDENCE5 (VIP5), a subunit of the PAF1 complex. Genetic analysis showed that VIP5 acts downstream of SPT5 and CDKD;2 Loss of SPT5 or CDKD;2 function results in early flowering because of decreased amounts of FLOWERING LOCUS C (FLC) transcript. Importantly, CDKD;2 and SPT5 are required for the deposition of VIP5 and the enhancement of trimethylation of histone 3 lysine 4 in the chromatin of the FLC locus. Together, our results provide insight into the mechanism by which the Arabidopsis elongation factor SPT5 recruits the PAF1 complex via the posttranslational modification of proteins and suggest that the phosphorylation of SPT5 by CDKD;2 enables it to recruit VIP5 to regulate chromatin and transcription in Arabidopsis.

Life history of Stenopsylla nigricornis (Hemiptera: Psylloidea: Triozidae) and phytohormones involved in its gall induction

Many phytophagous insects have an ability to manipulate plant tissue and induce galls, but the mechanism is not yet fully understood. Some insects have multivoltine life cycles, and each generation induces galls on different plant species or different organs in the same host. Such host-use patterns are interesting study subjects to clarify the gall-inducing mechanisms of insects. We focused on a multivoltine and gall-inducing psyllid Stenopsylla nigricornis Kuwayama (Hemiptera: Psylloidea: Triozidae), which is associated with Symplocos lucida Sieb. (Symplocaceae). Based on periodic field surveys in Kyushu, Japan, S. nigricornis is revealed to have a bivoltine life history. Then, we revealed that the spring generation induces galls on leaves, while the autumn generation does so on flower buds and overwintering leaf buds. We also analyzed phytohormones in normal plant tissue, S. nigricornis nymphs, and their galls. As a result, nymphs were discovered to contain much higher concentrations of isopentenyladenosine and its possible precursor, isopentenyladenosine riboside than plant tissues, strongly suggesting that the phytohormone is involved in gall induction by S. nigricornis. Because flower bud galls contained significantly lower concentrations of abscisic acid (ABA) than normal flower bud, the autumn generation nymphs are considered to regulate the ABA level and to promote the earlier opening of host flower buds.

Refinement of the collection of wild peas (Pisum L.) and search for the area of pea domestication with a deletion in the plastidic psbA-trnH spacer

The plastidic psbA-trnH spacer was sequenced in 78 accessions representing the genus Pisum L. A nucleotide substitution C64T in the spacer was found to be specific for Pisum abyssinicum A. Br.; a substitution T75G occurred in five accessions of the wild pea [Pisum sativum L. subsp. elatius (Bieb.) Schmalh.], one from France, three from Greece and one from Turkey, and also in a primitive landrace from Afghanistan with signs of contamination. A 7-bp tandem duplication was found in two P. sativum subsp. elatius accessions, from Turkey and Georgia. All (except for the probably contaminated Afghan accession) of the cultivated subspecies P. sativum L. subsp. sativum had a deletion of one copy of a tandem 8-bp repeat. The same deletion was found in two wild pea (P. sativum subsp. elatius) accessions, from Bulgaria and Georgia, belonging to the same earlier defined lineage B as the cultivated pea. They are supposed to represent the ancestral evolutionary lineage of the cultivated pea. It is noteworthy that accessions from the proposed Core Area of the Near East founder crop domestication in south-eastern Turkey do not have the deletion. Most of wild representatives of lineage B have a scarcely pigmented flower with almost non-opening standard, but those from Transcaucasia have a normal flower. The revealed area of co-existence of the earlier defined wild pea lineages A and B (differing in alleles of three molecular markers from different cellular genomes) was extended from Turkey to include Georgia and probably North Africa. Accessions claimed to represent wild peas were tested for spontaneous pod dehiscing and 14 of them were disproved as such. They are enriched with ‘recombinant’ marker combinations and most probably resulted from hybridisation of wild and cultivated peas, either in nature or while reproducing in germplasm collections.

Transcriptome analysis of the male-to-hermaphrodite sex reversal induced by low temperature in papaya

Papaya (Carica papaya L.) is a trioecious plant species, producing three sex forms, male, female, and hermaphrodite. Although the major sex types are genetically determined, the phenotypic sex expression of papaya is influenced by environmental factors. We investigated differential gene expression analysis between the non-functional rudimentary pistils from normal male flowers and developed and functional pistils from the male-to-hermaphrodite sex reversal flowers induced by low temperature aiming to understanding the gene regulatory network that determinates the phenotypic sex expression in papaya. Our differential gene expression analysis revealed 1756 differentially expressed genes between normal male and male-to-hermaphrodite sex reversal flowers. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analysis showed transcription factors, flower development, histone H3-K9 methylation, and plant hormone signal transduction were among the most significantly enriched GO terms and KEGG pathways. Small RNA analysis was also performed on the pistils from normal male and the male-to-hermaphrodite sex reversal flowers. Our result showed the 24 nt small RNAs were the most abundant in the pistils from both normal and sex reversal flowers, followed by 21 nt small RNAs. We detected expression of 40 plant-conserved miRNAs and 14 papaya-specific miRNAs in the pistils from one or both normal and sex reversal flowers. Sixteen miRNAs exhibited high-expression level and ten of them showed differential expression between the normal male and the male-to-hermaphrodite sex reversal flowers. Our results suggested the male-to-hermaphrodite sex reversal was likely caused by silencing the gynoecium suppression function on the sex determination pathway through epigenetic modification.

Diageotropica and Lateral Rooting, the Rest of the Story

Diageotropica and Lateral Rooting, the Rest of the Story

The Rosa chinensis cv. Viridiflora Phyllody Phenotype Is Associated with Misexpression of Flower Organ Identity Genes.

Phyllody is a flower abnormality in which leaf-like structures replace flower organs in all whorls. Here, we investigated the origin and the molecular mechanism of phyllody phenotype in Rosa chinensis cv. Viridiflora, an ancient naturally occurring Chinese mutant cultivar. Reciprocal grafting experiments and microscopy analyses, demonstrated that the phyllody phenotype in Viridiflora is not associated with phytoplasmas infection. Transcriptome comparisons by the mean of RNA-Seq identified 672 up-regulated and 666 down-regulated genes in Viridiflora compared to its closely related genotype R. chinensis cv. Old Blush. A fraction of these genes are putative homologs of genes known to be involved in flower initiation and development. We show that in flower whorl 2 of Viridiflora, a down-regulation of the floral organ identity genes RcPISTILLATA (RcPI), RcAPETALA3 (RcAP3) and RcSEPALLATA3 (RcSEP3), together with an up-regulation of the putative homolog of the gene SUPPRESSOR of OVEREXPRESSION of CONSTANS1 (RcSOC1) are likely at the origin of the loss of petal identity and leaf-like structures formation. In whorl 3 of Viridiflora, ectopic expression of RcAPETALA2 (RcAP2) along with the down regulation of RcPI, RcAP3, and RcSEP3 is associated with loss of stamens identity and leaf-like structures formation. In whorl 4, the ectopic expression of RcAP2 associated with a down-regulation of RcSEP3 and of the C-class gene RcAGAMOUS correlate with loss of pistil identity. The latter also suggested the antagonist effect between the A and C class genes in the rose. Together, these data suggest that modified expression of the ABCE flower organ identity genes is associated with the phyllody phenotype in the rose Viridiflora and that these genes are important for normal flower organs development.

A Comparative study on pytoconstitutents of Punica granatum flowers of Normal and Ornamental variety using TLC/HPTLC methods

Punica granatum is a shrub that has a bushy appearance, have a good n umber of varieties, cultivated either as commercial crop for the production of pomegranates or as an ornamental crop for its beautiful flo wers. Among the ornamental crop of Punica granatum, the “Double flower” producing plant gains much significant value as it is used in Unani drug un der the name of Gulnar for treating many ailments. The present study was aimed to investigate and compare the phytoconstitutents present in both the flowers using TLC and HP TLC methods. The normal and double flo wers of P. granatum were extracted with chloroform and alcohol separately using soxhlet apparatus. The TLC and HPTLC finger print profile of the extracts with marker compounds were studied using HPTLC Instrument, CAMAG (Switzerland). The TLC and HPTLC profile of chloroform and alcohol extract of normal and double flowers of P. granatum were exploited. The compound gallic acid and ethyl gallate, chromatographed together served as marker compound. The results revealed th e similar and different phytoconstituents of both the flowers. The TLC and HPTLC finger print chromatograms not only demonstrates the similarities and differences bet ween the flowers but also sho ws the presence of tested marker compounds gallic acid and ethyl gallate in alcohol extracts of both the flower types apart from acting as a quality control tool.

Arabidopsis cryptochrome 1 functions in nitrogen regulation of flowering

The phenomenon of delayed flowering after the application of nitrogen (N) fertilizer has long been known in agriculture, but the detailed molecular basis for this phenomenon is largely unclear. Here we used a modified method of suppression-subtractive hybridization to identify two key factors involved in N-regulated flowering time control in Arabidopsis thaliana, namely ferredoxin-NADP(+)-oxidoreductase and the blue-light receptor cryptochrome 1 (CRY1). The expression of both genes is induced by low N levels, and their loss-of-function mutants are insensitive to altered N concentration. Low-N conditions increase both NADPH/NADP(+) and ATP/AMP ratios, which in turn affect adenosine monophosphate-activated protein kinase (AMPK) activity. Moreover, our results show that the AMPK activity and nuclear localization are rhythmic and inversely correlated with nuclear CRY1 protein abundance. Low-N conditions increase but high-N conditions decrease the expression of several key components of the central oscillator (e.g., CCA1, LHY, and TOC1) and the flowering output genes (e.g., GI and CO). Taken together, our results suggest that N signaling functions as a modulator of nuclear CRY1 protein abundance, as well as the input signal for the central circadian clock to interfere with the normal flowering process.

Gene Mapping of a Mutant Mungbean (Vigna radiata L.) Using New Molecular Markers Suggests a Gene Encoding a YUC4-like Protein Regulates the Chasmogamous Flower Trait

Mungbean (Vigna radiata L.) is a cleistogamous plant in which flowers are pollinated before they open, which prevents yield improvements through heterosis. We previously generated a chasmogamous mutant (CM) mungbean in which open flowers are pollinated. In this study, we developed insertion/deletion (indel) markers based on the transcriptome differences between CM and Sulu-1 (i.e., normal flowering) plants. An F2 population derived from a cross between CM and Sulu-1 was used for gene mapping. Segregation analyses revealed that a single recessive gene regulates the production of chasmogamous flowers. Using newly developed indel and simple sequence repeat markers, the cha gene responsible for the chasmogamous flower trait was mapped to a 277.1-kb segment on chromosome 6. Twelve candidate genes were detected in this segment, including Vradi06g12650, which encodes a YUCCA family protein associated with floral development. A single base pair deletion producing a frame-shift mutation and a premature stop codon in Vradi06g12650 was detected only in CM plants. This suggested that Vradi06g12650 is a cha candidate gene. Our results provide important information for the molecular breeding of chasmogamous mungbean lines, which may serve as new genetic resources for hybrid cultivar development.

Plant Regeneration from Leaf-derived Callus Cultures of Primrose (Primula vulgaris)

Efficient micropropagation of Primula species is important both for fundamental scientific studies and commercial applications. Primula vulgaris (Huds), along with other Primulaceae species, exhibits floral heteromorphy with two distinct forms of hermaphroditic flower. Studies to identify genes that control heteromorphic flower development require propagation of floral mutants, and efficient regeneration is a key requirement for plant transformation. Several species, including P. vulgaris cultivars and P. ×polyantha hybrids, are important horticultural crops in Europe, United States, and Japan and semidouble/double Primula varieties offer a high-end product. Vegetative propagation of sterile double forms, and as a means to increase numbers of inbred parent plants for F1 seed production is, however, slow. Micropropagation offers the most efficient way of increasing these varieties quickly and efficiently. To date, most Primula micropropagation protocols require explant material derived from in vitro grown seedlings or use floral parts as donor material with seasonal limitations. Therefore, an effective and efficient protocol was developed for in vitro regeneration of P. vulgaris via indirect organogenesis from adult leaf–derived explants. Exposure of leaf explants of P. vulgaris to media containing synthetic cytokinin, thidiazuron (TDZ), and auxin [1-naphthylacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D)] resulted in undifferentiated cell proliferation and followed by differentiated growth as shoot organogenesis. Silver nitrate improved in vitro callus growth and increased shoot regeneration further, with up to 72% of explants producing shoots. Regenerated plants developed normally and produced normal fertile flowers within 7 months. The system was also successfully applied for the micropropagation of sterile double-flowered P. vulgaris ‘Sue Jervis’. The protocol reported here enables propagation of P. vulgaris without seasonal limitation or destruction of valuable parent donor material. The protocol, with further development, has the potential to underpin development of a transformation system for Primula, which would be of value in studies on flower development and disease resistance in laboratory grown plants.