Effects of SvAPETALA1-5 gene on floral organ development in Senecio vulgaris.

Asteraceae is a large class of eudicots with complex capitulum, and little is known regarding the molecular regulation mechanism of flower development. APETALA1(AP1) belongs to the MADS-box gene family and plays a key role in plant floral induction and floral organ development. In this study, the bioinformatics and tissue-specific expression of AP1 homologous gene SvAP1-5 in Senecio vulgaris were analyzed. Based on VIGS technology, SvAP1-5 gene silencing plants were created, and SvAP1-5 was overexpressed in Solanum nigrum. The results of bioinformatics analysis showed that SvAP1-5 gene had typical MADS-box and K-box structure, and contains FUL motif and paleoAP1 motif at the C-terminal. SvAP1-5 belongs to the euFUL branch of AP1 gene. qRT-PCR results showed that SvAP1-5 was expressed in bracts, petals and carpels, and was highly expressed in carpels. Compared with the control group, SvAP1-5 gene silencing resulted in irregular petal dehiscence, increased stigma division, and carpel dysplasia. The fruit development of SvAP1-5 overexpressing S.nigrum plants was abnormal, and the hyperplastic tissue similar to fruit appeared. In summary, SvAP1-5 gene may be involved in the development of petals and carpels and plays an important role during the development of S.vulgaris.

Establishment of a high-efficiency transformation and genome editing method for an essential vegetable and medicine Solanum nigrum.

Solanum nigrum, which belongs to the Solanaceae family, is an essential plant for food and medicine. It has many important secondary compounds, including glycoproteins, glycoalkaloids, polyphenolics, and anthocyanin-rich purple berries, as well as many ideal characteristics such as self-fertilization, a short life cycle and a small genome size that make it a potential model plant for the study of secondary metabolism and fruit development. In this study, we report a highly efficient and convenient tissue culture, transformation and genome editing method for S. nigrum using leaf segments after 8 weeks of tissue culture, with a required period from transformation initiation to harvest of about 3.5 months. Our results also show multi-shoot regeneration per leaf segment and a 100% shoot regeneration efficiency in a shoot regeneration medium. Moreover, over 82% of kanamycin-resistant plants exhibited strong green fluorescence marker protein expression, with genetic integration confirmed by PCR results and green fluorescence protein expression in their T1 progeny. Furthermore, we successfully applied this transformation method to achieve an average of 83% genome editing efficiency of SnMYB1, a gene involved in regulating the anthocyanin biosynthetic pathway of S. nigrum in response to missing nutrients. Taken together, the combination of highly efficient tissue culture, transformation and genome editing systems can provide a powerful platform for supporting fundamental research on the molecular mechanisms of secondary metabolism, fruit development, and production of important compounds by biotechnology.

Cloning and functional analysis of RADIALIS-like 1 gene from Antirrhinum majus.

MYB is one of the largest transcription factor families in plants. Among them, the R3-MYB transcription factor RADIALIS (RAD) plays a very important role in the flowers development in Antirrhinum majus. In this study, a R3-MYB gene similar to RAD was found by analyzing the genome of A. majus, which was named AmRADIALIS-like 1 (AmRADL1). The gene function was predicted through bioinformatics. The relative expression levels in different tissues and organs of wild-type A. majus were analyzed by qRT-PCR. AmRADL1 was overexpressed in A. majus, and the transgenic plants were analyzed by morphological observation and histological staining. The results showed that the open reading frame (ORF) of AmRADL1 gene was 306 bp in length, encoding 101 amino acids. It has typical SANT domain, and the C-terminal contains a CREB motif, which was highly homologous to tomato SlFSM1. The results of qRT-PCR showed that AmRADL1 was expressed in roots, stems, leaves and flowers, and the expression level was higher in flowers. Further analysis of its expression in different floral organs showed that AmRADL1 had the highest expression in carpel. The results of histological staining analysis of the transgenic plants showed that compared with the wild type, although the size of the carpel cells of the transgenic plants did not change significantly, the placenta area in the carpel became smaller and the number of cell decreased. In summary, AmRADL1 may be involved in the regulation of carpel development, but the specific mechanism of action in carpel remains to be further studied.

Shaping of a three-dimensional carnivorous trap through modulation of a planar growth mechanism.

Leaves display a remarkable range of forms, from flat sheets with simple outlines to cup-shaped traps. Although much progress has been made in understanding the mechanisms of planar leaf development, it is unclear whether similar or distinctive mechanisms underlie shape transformations during development of more complex curved forms. Here, we use 3D imaging and cellular and clonal analysis, combined with computational modelling, to analyse the development of cup-shaped traps of the carnivorous plant Utricularia gibba. We show that the transformation from a near-spherical form at early developmental stages to an oblate spheroid with a straightened ventral midline in the mature form can be accounted for by spatial variations in rates and orientations of growth. Different hypotheses regarding spatiotemporal control predict distinct patterns of cell shape and size, which were tested experimentally by quantifying cellular and clonal anisotropy. We propose that orientations of growth are specified by a proximodistal polarity field, similar to that hypothesised to account for Arabidopsis leaf development, except that in Utricularia, the field propagates through a highly curved tissue sheet. Independent evidence for the polarity field is provided by the orientation of glandular hairs on the inner surface of the trap. Taken together, our results show that morphogenesis of complex 3D leaf shapes can be accounted for by similar mechanisms to those for planar leaves, suggesting that simple modulations of a common growth framework underlie the shaping of a diverse range of morphologies.

Functional analysis of flower development related gene SvGLOBOSA from Senecio vulgaris.

The unique capitulum of Asteraceae has important ornamental and research value. Few studies have described the complex molecular mechanism of flower development. In this study, SvGLOBOSA(SvGLO), the MADS-box gene of Senecio vulgaris, was identified by screening the transcriptome data, and its function was examined. The gene structure was analyzed and its function was predicted through bioinformatics. The relative expression levels in different tissues of wild-type S. vulgaris were analyzed by qRT-PCR. SvGLO was overexpressed in Solanum nigrum and morphological observations were made. Histological staining was used in analyzing the histological changes in the ovary of transgenic S. nigrum. The results showed that the open reading frame of SvGLO was 591 bp long, encoding 196 amino acids. It has typical MADS-box and K-box domains and contains a PI motif at the C-terminal. SvGLO belongs to the PI/GLO subfamily of class B MADS-box genes. qRT-PCR results showed that SvGLO was highly expressed in inflorescence tissues but not in vegetative organs. In SvGLO-overexpressed S. nigrum, the sepals showed some characteristics of petals, carpels transformed into stamen-like organs, and fruit development was abnormal. Histological staining revealed that the morphology of ovary wall cells of transgenic S. nigrum was similar to that of anther wall cells of the stamen of wild-type S. vulgaris. Therefore, SvGLO may be involved in the regulation of petal and stamen development in S. vulgaris.

Quantitative control of organ shape by combinatorial gene activity.

The development of organs with particular shapes, like wings or flowers, depends on regional activity of transcription factors and signalling molecules. However, the mechanisms that link these molecular activities to the morphogenetic events underlying shape are poorly understood. Here we describe a combination of experimental and computational approaches that address this problem, applying them to a group of genes controlling flower shape in the Snapdragon (Antirrhinum). Four transcription factors are known to play a key role in the control of floral shape and asymmetry in Snapdragon. We use quantitative shape analysis of mutants for these factors to define principal components underlying flower shape variation. We show that each transcription factor has a specific effect on the shape and size of regions within the flower, shifting the position of the flower in shape space. These shifts are further analysed by generating double mutants and lines that express some of the genes ectopically. By integrating these observations with known gene expression patterns and interactions, we arrive at a combinatorial scheme for how regional effects on shape are genetically controlled. We evaluate our scheme by incorporating the proposed interactions into a generative model, where the developing flower is treated as a material sheet that grows according to how genes modify local polarities and growth rates. The petal shapes generated by the model show a good quantitative match with those observed experimentally for each petal in numerous genotypes, thus validating the hypothesised scheme. This article therefore shows how complex shapes can be accounted for by combinatorial effects of transcription factors on regional growth properties. This finding has implications not only for how shapes develop but also for how they may have evolved through tinkering with transcription factors and their targets.

The R2R3-MYB gene CgMYB4 is involved in the regulation of cell differentiation and fiber development in the stamens of Chelone glabra L.

A Plantaginaceae flowering plant, Chelone glabra, is different from Arabidopsis thaliana and cotton (Gossypium hirsutum), as it produces fibers on the anther surface. However, the evolutionary molecular mechanism of how fiber development is controlled in the stamen is unclear. MYB genes are essential transcription factors for trichome and fiber development in plants. In this study, we isolated 29 MYB domain-containing sequences using early-stage anthers and several sets of degenerated primers conserved in the R2R3 domain of the MYB transcription factor. Among them, CgMYB4 is an R2R3-MYB gene encoding 281 amino acids. Phylogenetic analysis showed that CgMYB4 is closely related to GhMYB25L/AmMIXTA, which controls fiber initiation and development in cotton and epidermal cell differentiation in the petals of Antirrhinum. Semiquantitative RT-PCR analysis showed that CgMYB4 is strongly expressed at the stamens and carpels. Overexpression of CgMYB4 significantly enhanced root hair formation in transformed hairy roots, contrary to the root hair numbers, which were reduced in silenced CgMYB4 hairy roots. Moreover, overexpression of CgMYB4 also evidently promoted fiber development at filaments and conical cell-like epidermal cell increases at the anther wall. Our results showed that CgMYB4 is an R2R3-MYB gene and is positively involved in regulating cell division and fiber differentiation in the early stages of stamen development in C. glabra.

The combination of R2R3-MYB gene AmRosea1 and hairy root culture is a useful tool for rapidly induction and production of anthocyanins in Antirrhinum majus L.

Anthocyanins are the largest group of water-soluble pigments and beneficial for human health. Although most plants roots have the potential to express natural biosynthesis pathways required to produce specialized metabolites such as anthocyanins, the anthocyanin synthesis is specifically silenced in roots. To explore the molecular mechanism of absence and production ability of anthocyanin in the roots, investigated the effect of a bHLH gene AmDelila, and an R2R3-MYB gene AmRosea1, which are the master regulators of anthocyanin biosynthesis in Antirrhinum majus flowers, by expressing these genes in transformed hairy roots of A. majus. Co-ectopic expression of both AmDelila and AmRosea1 significantly upregulated the expression of the key target structural genes in the anthocyanin biosynthesis pathway. Furthermore, this resulted in strongly enhanced anthocyanin accumulation in transformed hairy roots. Ectopic expression of AmDelila alone did not gives rise to any significant anthocyanin accumulation, however, ectopic expression of AmRosea1 alone clearly upregulated expression of the main structural genes as well as greatly promoted anthocyanin accumulation in transformed hairy roots, where the contents reached 0.773-2.064 mg/g fresh weight. These results suggest that AmRosea1 plays a key role in the regulatory network in controlling the initiation of anthocyanin biosynthesis in roots, and the combination of AmRosea1 and hairy root culture is a powerful tool to study and production of anthocyanins in the roots of A. majus.

A Stable Agrobacterium rhizogenes-Mediated Transformation of Cotton (Gossypium hirsutum L.) and Plant Regeneration From Transformed Hairy Root via Embryogenesis.

Genetic transformation is a powerful tool to study gene function, secondary metabolism pathways, and molecular breeding in crops. Cotton (Gossypium hirsutum L.) is one of the most important economic crops in the world. Current cotton transformation methods take at least seven to culture and are labor-intensive and limited to some cultivars. In this study, we first time achieved plantlet regeneration of cotton via embryogenesis from transformed hairy roots. We inoculated the cotyledon explants of a commercial cultivar Zhongmian-24 with Agrobacterium rhizogenes strain AR1193, harboring a binary vector pBI-35S::GFP that contained the NPT II (neomycin phosphotransferase) gene and the GFP (green fluorescent protein) gene as a fluorescent marker in the T-DNA region. 82.6% explants produced adventitious roots, of which 53% showed GFP expression after transformation. 82% of transformed hairy roots produced embryonic calli, 12% of which regenerated into stable transformed cotton plants after 7 months of culture. The integration of GFP in the transformed cotton genomes were confirmed by PCR (Polymerase chain reaction) and Southern blot analysis as well as the stable expression of GFP were also detected by semi-quantitative RT-PCR analysis. The resultant transformed plantlets were phenotypically, thus avoiding Ri syndrome. Here we report a stable and reproducible method for A. rhizogenes-mediated transformation of cotton using cotyledon as explants, which provides a useful and reliable platform for gene function analysis of cotton.

Evolution of carnivorous traps from planar leaves through simple shifts in gene expression.

Leaves vary from planar sheets and needle-like structures to elaborate cup-shaped traps. Here, we show that in the carnivorous plant Utricularia gibba, the upper leaf (adaxial) domain is restricted to a small region of the primordium that gives rise to the trap's inner layer. This restriction is necessary for trap formation, because ectopic adaxial activity at early stages gives radialized leaves and no traps. We present a model that accounts for the formation of both planar and nonplanar leaves through adaxial-abaxial domains of gene activity establishing a polarity field that orients growth. In combination with an orthogonal proximodistal polarity field, this system can generate diverse leaf forms and account for the multiple evolutionary origins of cup-shaped leaves through simple shifts in gene expression.

Functional expression of the taste-modifying protein, miraculin, in transgenic lettuce.

Taste-modifying proteins are a natural alternative to artificial sweeteners and flavor enhancers and have been used in some cultures for centuries. The taste-modifying protein, miraculin, has the unusual property of being able to modify a sour taste into a sweet taste. Here, we report the use of a plant expression system for the production of miraculin. A synthetic gene encoding miraculin was placed under the control of constitutive promoters and transferred to lettuce. Expression of this gene in transgenic lettuce resulted in the accumulation of significant amounts of miraculin protein in the leaves. The miraculin expressed in transgenic lettuce possessed sweetness-inducing activity. These results demonstrate that the production of miraculin in edible plants can be a good alternative strategy to enhance the availability of this protein.

A rapid and stable Agrobacterium-mediated transformation method of a medicinal plant Chelone glabra L.

Transformation approach is a useful tool for the study of gene function, the mechanism of molecular regulation, and increase usefulness of components by reverse genetic approach in plants. In this study, we developed a stable and rapid method for Agrobacterium-mediated transformation of a medicinal plant Chelone glabra L. using leaf explants. Stable transformants were obtained using Agrobacterium tumefaciens strains GV2260 and GV3101 that harbored the binary vector pBI121 and contained the neomycin phosphotransferase gene (NPT II) as a selectable marker and a reporter gene ß-glucuronidase (GUS). Putative transformants were identified by kanamycin selection and a histochemical assay. PCR and Southern blot analysis confirmed the integration of the GUS gene into transformed genomes as well as detected stable expression of the ß-glucuronidase gene (GUS) by RT-PCR. Resulting transformed plants had morphologically normal phenotypes. This method requires two changes of medium and few leaf explants as well as the transformation efficiency of 2-8 % after 2-3 months of inoculation. This method can provide a quick and economical transformation method for reverse genetic approach to change the secondary metabolic pathway to increase useful components in C. glabra.

A stable and efficient Agrobacterium tumefaciens-mediated genetic transformation of the medicinal plant Digitalis purpurea L.

In this study, we developed a rapid and efficient method for in vitro propagation and Agrobacterium tumefaciens-mediated transformation of Digitalis purpurea L. (syn. foxglove), an important medicinal plant. Mature leaf explants of D. purpurea were used for 100 % adventitious shoot regeneration on Murashige and Skoog (MS) medium supplemented with 1 mg L(-1) thidiazuron (TDZ) (a cytokine) and 0.1 mg L(-1) 1-naphthaleneacetic acid (NAA) (an auxin). Transformation was achieved by inoculating leaf explants with the A. tumefaciens strains GV2260/pBI121 or GV3101/pBI121. The binary vector pBI121 contained the reporter ß-glucuronidase gene (GUS) and kanamycin selection marker nptII. Kanamycin-resistant shoots were regenerated directly on the selection medium 4-6 weeks after co-cultivation. Approximately, 52.2 and 60 % of kanamycin-resistant shoots transformed with Agrobacterium strains GV2260 and GV3101, respectively, showed strong GUS staining by histochemical assay. Furthermore, PCR and Southern blot analysis confirmed the presence of nptII and GUS on the chromosome of the transformed D. purpurea plants, and stable GUS expression was detected in the transformants by RT-PCR analysis. This efficient method of shoot regeneration and genetic transformation of D. purpurea will provide a powerful tool to increase and produce valuable components such as digitoxin, digoxin, and digoxigenin in D. purpurea through improved secondary metabolic pathways via a biotechnological approach.

The promoter structure differentiation of a MYB transcription factor RLC1 causes red leaf coloration in Empire Red Leaf Cotton under light.

The red leaf coloration of Empire Red Leaf Cotton (ERLC) (Gossypium hirsutum L.), resulted from anthocyanin accumulation in light, is a well known dominant agricultural trait. However, the underpin molecular mechanism remains elusive. To explore this, we compared the molecular biological basis of anthocyanin accumulation in both ERLC and the green leaf cotton variety CCRI 24 (Gossypium hirsutum L.). Introduction of R2R3-MYB transcription factor Rosea1, the master regulator anthocyanin biosynthesis in Antirrhinum majus, into CCRI 24 induced anthocyanin accumulation, indicating structural genes for anthocyanin biosynthesis are not defected and the leaf coloration might be caused by variation of regulatory genes expression. Expression analysis found that a transcription factor RLC1 (Red Leaf Cotton 1) which encodes the ortholog of PAP1/Rosea1 was highly expressed in leaves of ERLC but barely expressed in CCRI 24 in light. Ectopic expression of RLC1 from ERLC and CCRI 24 in hairy roots of Antirrhinum majus and CCRI 24 significantly enhanced anthocyanin accumulation. Comparison of RLC1 promoter sequences between ERLC and CCRI 24 revealed two 228-bp tandem repeats presented in ERLC with only one repeat in CCRI 24. Transient assays in cotton leave tissue evidenced that the tandem repeats in ERLC is responsible for light-induced RLC1 expression and therefore anthocyanin accumulation. Taken together, our results in this article strongly support an important step toward understanding the role of R2R3-MYB transcription factors in the regulatory menchanisms of anthocyanin accumulation in red leaf cotton under light.

Regulatory genes control a key morphological and ecological trait transferred between species.

Hybridization between species can lead to introgression of genes from one species to another, providing a potential mechanism for preserving and recombining key traits during evolution. To determine the molecular basis of such transfers, we analyzed a natural polymorphism for flower-head development in Senecio. We show that the polymorphism arose by introgression of a cluster of regulatory genes, the RAY locus, from the diploid species S. squalidus into the tetraploid S. vulgaris. The RAY genes are expressed in the peripheral regions of the inflorescence meristem, where they promote flower asymmetry and lead to an increase in the rate of outcrossing. Our results highlight how key morphological and ecological traits controlled by regulatory genes may be gained, lost, and regained during evolution.

Subcellular localization and membrane topology of the melon ethylene receptor CmERS1.

Ethylene receptors are multispanning membrane proteins that negatively regulate ethylene responses via the formation of a signaling complex with downstream elements. To better understand their biochemical functions, we investigated the membrane topology and subcellular localization of CmERS1, a melon (Cucumis melo) ethylene receptor that has three putative transmembrane domains at the N terminus. Analyses using membrane fractionation and green fluorescent protein imaging approaches indicate that CmERS1 is predominantly associated with the endoplasmic reticulum (ER) membrane. Detergent treatments of melon microsomes showed that the receptor protein is integrally bound to the ER membrane. A protease protection assay and N-glycosylation analysis were used to determine membrane topology. The results indicate that CmERS1 spans the membrane three times, with its N terminus facing the luminal space and the large C-terminal portion lying on the cytosolic side of the ER membrane. This orientation provides a platform for interaction with the cytosolic signaling elements. The three N-terminal transmembrane segments were found to function as topogenic sequences to determine the final topology. High conservation of these topogenic sequences in all ethylene receptor homologs identified thus far suggests that these proteins may share the same membrane topology.