Enhanced fluorescence imaging in chlorophyll-suppressed tobacco tissues using virus-induced gene silencing of the phytoene desaturase gene

Bisphenol A affects the development and the onset of photosymbiosis in the acoel Symsagittiferaroscoffensis

Photosymbiosis indicates a long-term association between animals and photosynthetic organisms. It has been mainly investigated in photosymbiotic cnidarians, while other photosymbiotic associations have been largely neglected. The acoel Symsagittifera roscoffensis lives in obligatory symbiosis with the microalgal Tetraselmis convolutae and has recently emerged as alternative model to study photosymbiosis. Here, we investigated the effects of Bisphenol A, a common plastic additive, on two pivotal stages of its lifecycle: aposymbiotic juvenile development and photosymbiogenesis. Based on our results, this pollutant altered the development of the worms and their capacity to engulf algae from the environment at concentrations higher than the levels detected in seawater, yet aligning with those documented in sediments of populated areas. Data provide novel information about the effects of pollutants on photosymbiotic associations and prompt the necessity to monitor their concentrations in marine environmental matrices.

Fluorescent in vivo imaging of reactive oxygen species and redox potential in plants

Reactive oxygen species (ROS) are by-products of aerobic metabolism, and excessive production can result in oxidative stress and cell damage. In addition, ROS function as cellular messengers, working as redox regulators in a multitude of biological processes. Understanding ROS signalling and stress responses requires methods for precise imaging and quantification to monitor local, subcellular and global ROS dynamics with high selectivity, sensitivity and spatiotemporal resolution. In this review, we summarize the present knowledge for in vivo plant ROS imaging and detection, using both chemical probes and fluorescent protein-based biosensors. Certain characteristics of plant tissues, for example high background autofluorescence in photosynthetic organs and the multitude of endogenous antioxidants, can interfere with ROS and redox potential detection, making imaging extra challenging. Novel methods and techniques to measure in vivo plant ROS and redox changes with better selectivity, accuracy, and spatiotemporal resolution are therefore desirable to fully acknowledge the remarkably complex plant ROS signalling networks.

Nicotiana attenuata's capacity to interact with arbuscular mycorrhiza alters its competitive ability and elicits major changes in the leaf transcriptome

To study the local and systemic effects of arbuscular mycorrhizal fungal (AMF) colonization, Nicotiana attenuata plants impaired in their interactions with AMF due to silencing of a calcium- and calmodulin dependent protein kinase (inverted repreat (ir)CCaMK) were grown competitively in pairs with empty vector (EV) plants, with and without two different types of inoculum. When inoculated, EV plants strongly outperformed irCCaMK plants. Foliar transcript profiling revealed that AMF colonization significantly changed gene expression of P-starvation and -transporter genes in irCCaMK plants. The Pht1 family phosphate transporter NaPT5 was not only specifically induced in roots after AMF colonization, but also in leaves of AMF-colonized irCCaMK plants, and in plants grown under low Pi conditions in the absence of AMF. The P-starvation signature of inoculated irCCaMK plants corresponded with increases in selected amino acids and phenolic compounds in leaves. We also found a strong AMF-induced increase in amino acids and phenolic metabolites in roots. Plants impaired in their interactions with AMF clearly have a fitness disadvantage when competing for limited soil nutrients with a fully functional isogenic line. The additional role of the AMF-induced Pht1 family transporter NaPT5 in leaves under P-starvation conditions will require further experiments to fully resolve.

Time Gating of Chloroplast Autofluorescence Allows Clearer Fluorescence Imaging In Planta

Chloroplast, an organelle facilitating photosynthesis, exhibits strong autofluorescence, which is an undesired background signal that restricts imaging experiments with exogenous fluorophore in plants. In this study, the autofluorescence was characterized in planta under confocal laser microscopy, and it was found that the time-gated imaging technique completely eliminates the autofluorescence. As a demonstration of the technique, a clearer signal of fluorescent protein-tagged phototropin, a blue-light photoreceptor localized at the chloroplast periphery, was visualized in planta.

Fluorescence imaging for Fe3+ in Arabidopsis by using simple naphthalene-based ligands

Naphthalene-based probes 1 and 1A were found to dramatically decrease fluorescence upon addition of Fe³⁺, but not with other metal ions. Furthermore, 1 and 1A displayed high fluorescence quenched-imaging for Fe³⁺ in Arabidopsis as well as nanofibruous films.

In vivo detection of fluoride at trace levels and its removal from raw water at neutral pH utilizing a cyanobacterium pigment as a luminescent probe

A selective method has been developed for trace level (0.01 mg L⁻¹) fluoride detection in HEPES buffer in the presence of interfering ions (such as Cl⁻, I⁻, Br⁻, SO₄²⁻, ClO₄⁻, and CH₃COO⁻) using a cyanobacterium as a luminescent probe.

High selective fluorescence imaging of cesium distribution in Arabidopsis using a bis(trihydroxyphenyl)-appended fluorescent probe with a turn-on system

The bis(trihydroxyphenyl)-appended ligand 1 was found to display dramatically enhanced fluorescence upon the addition of Cs⁺, but not with any other metal ions.

Assessing the tobacco-rattle-virus-based vectors system as an efficient gene silencing technique in Datura stramonium (Solanaceae)

Datura stramonium is a well-known medicinal plant, which is important for its alkaloids. There are intrinsic limitations for the natural production of alkaloids in plants; metabolic engineering methods can be effectively used to conquer these limitations. In order for this the genes involved in corresponding pathways need to be studied. Virus-Induced Gene Silencing is known as a functional genomics technique to knock-down expression of endogenous genes. In this study, we silenced phytoene desaturase as a marker gene in D. stramonium in a heterologous and homologous manner by tobacco-rattle-virus-based VIGS vectors. Recombinant TRV vector containing pds gene from D. stramonium (pTRV2-Dspds) was constructed and injected into seedlings. The plants injected with pTRV2-Dspds showed photobleaching 2 weeks after infiltration. Spectrophotometric analysis demonstrated that the amount of chlorophylls and carotenoids in leaves of the bleached plants decreased considerably compared to that of the control plants. Semi-Quantitative RT-PCR results also confirmed that the expression of pds gene in the silenced plants was significantly reduced in comparison with the control plants. The results showed that the viral vector was able to influence the levels of total alkaloid content in D. stramonium. Our results illustrated that TRV-based VIGS vectors are able to induce effective and reliable functional gene silencing in D. stramonium as an alternative tool for studying the genes of interest in this plant, such as the targeted genes in tropane alkaloid biosynthetic pathway. The present work is the first report of establishing VIGS as an efficient method for transient silencing of any gene of interest in D. stramonium.

'Real time' genetic manipulation: a new tool for ecological field studies

Field experiments with transgenic plants often reveal the functional significance of genetic traits that are important for the performance of the plants in their natural environments. Until now, only constitutive overexpression, ectopic expression and gene silencing methods have been used to analyze gene-related phenotypes in natural habitats. These methods do not allow sufficient control over gene expression for the study of ecological interactions in real time, of genetic traits that play essential roles in development, or of dose-dependent effects. We applied the sensitive dexamethasone (DEX)-inducible pOp6/LhGR expression system to the ecological model plant Nicotiana attenuata and established a lanolin-based DEX application method to facilitate ectopic gene expression and RNA interference-mediated gene silencing in the field and under challenging conditions (e.g. high temperature, wind and UV radiation). Fully established field-grown plants were used to silence phytoene desaturase and thereby cause photobleaching only in specific plant sectors, and to activate expression of the cytokinin (CK) biosynthesis gene isopentenyl transferase (ipt). We used ipt expression to analyze the role of CKs in both the glasshouse and the field to understand resistance to the native herbivore Tupiocoris notatus, which attacks plants at small spatial scales. By spatially restricting ipt expression and elevating CK levels in single leaves, damage by T. notatus increased, demonstrating the role of CKs in this plant-herbivore interaction at a small scale. As the arena of most ecological interactions is highly constrained in time and space, these tools will advance the genetic analysis of dynamic traits that matter for plant performance in nature.

Overexpression of RoDELLA impacts the height, branching, and flowering behaviour of Pelargonium × domesticum transgenic plants

KEY MESSAGE : We reported the cloning of a rose DELLA gene. We obtained transgenic Pelargonium lines overexpressing this gene which presented several phenotypes in plant growth, root growth, flowering time and number of inflorescences. Control of development is an important issue for production of ornamental plant. The plant growth regulator, gibberellins (GAs), plays a pivotal role in regulating plant growth and development. DELLA proteins are nuclear negative regulator of GA signalling. Our objective was to study the role of GA in the plant architecture and in the blooming of ornamentals. We cloned a rose DELLA homologous gene, RoDELLA, and studied its function by genetic transformation of pelargonium. Several transgenic pelargonium (Pelargonium × domesticum 'Autum Haze') lines were produced that ectopically expressed RoDELLA under the control of the 35S promoter. These transgenic plants exhibited a range of phenotypes which could be related to the reduction in GA response. Most of transgenic plants showed reduced growth associated to an increase of the node and branch number. Moreover, overexpression of RoDELLA blocked or delayed flowering in transgenic pelargonium and exhibited defects in the root formation. We demonstrated that pelargonium could be used to validate ornamental gene as the rose DELLA gene. RoDELLA overexpression modified many aspects of plant developmental pathways, as the plant growth, the transition of vegetative to floral stage and the ability of rooting.

High level transgenic expression of soybean (Glycine max) GmERF and Gmubi gene promoters isolated by a novel promoter analysis pipeline

BACKGROUND

Although numerous factors can influence gene expression, promoters are perhaps the most important component of the regulatory control process. Promoter regions are often defined as a region upstream of the transcriptional start. They contain regulatory elements that interact with regulatory proteins to modulate gene expression. Most genes possess their own unique promoter and large numbers of promoters are therefore available for study. Unfortunately, relatively few promoters have been isolated and characterized; particularly from soybean (Glycine max).

RESULTS

In this research, a bioinformatics approach was first performed to identify members of the Gmubi (G.max ubiquitin) and the GmERF (G. max Ethylene Response Factor) gene families of soybean. Ten Gmubi and ten GmERF promoters from selected genes were cloned upstream of the gfp gene and successfully characterized using rapid validation tools developed for both transient and stable expression. Quantification of promoter strength using transient expression in lima bean (Phaseolus lunatus) cotyledonary tissue and stable expression in soybean hairy roots showed that the intensity of gfp gene expression was mostly conserved across the two expression systems. Seven of the ten Gmubi promoters yielded from 2- to 7-fold higher expression than a standard CaMV35S promoter while four of the ten GmERF promoters showed from 1.5- to 2.2-times higher GFP levels compared to the CaMV35S promoter. Quantification of GFP expression in stably-transformed hairy roots of soybean was variable among roots derived from different transformation events but consistent among secondary roots, derived from the same primary transformation events. Molecular analysis of hairy root events revealed a direct relationship between copy number and expression intensity; higher copy number events displayed higher GFP expression.

CONCLUSION

In this study, we present expression intensity data on 20 novel soybean promoters from two different gene families, ubiquitin and ERF. We also demonstrate the utility of lima bean cotyledons and soybean hairy roots for rapid promoter analyses and provide novel insights towards the utilization of these expression systems. The soybean promoters characterized here will be useful for production of transgenic soybean plants for both basic research and commercial plant improvement.