A protocol combining multiphoton microscopy and propidium iodide for deep 3D root meristem imaging in rice: application for the screening and identification of tissue-specific enhancer trap lines

Root Hair Imaging Using Confocal Microscopy

Plant genetics plays a key role in determining root hair initiation and development. A complex network of genetic interactions therefore closely monitors and influences root hair phenotype and morphology. The significance of these genes can be studied by employing, for instance, loss-of-function mutants, overexpression plant lines, and fluorescently labeled constructs. Confocal laser scanning microscopy is a great tool to visually observe and document these morphological features. This chapter elaborates the techniques involved in handling of microscopic setup to acquire images displaying root hair distribution along the fully elongated zone of Arabidopsis thaliana roots. Additionally, we illustrate an approach to visualize early fate determination of epidermal cells in the root apical meristem, by describing a method for imaging YFP tagged transgenic plant lines.

Quantitative Live Confocal Imaging in AquilegiaFloral Meristems

In this study, we present a detailed protocol for live imaging and quantitative analysis of floral meristem development in Aquilegia coerulea, a member of the buttercup family (Ranunculaceae). Using confocal microscopy and the image analysis software MorphoGraphX, we were able to examine the cellular growth dynamics during floral organ primordia initiation, and the transition from floral meristem proliferation to termination. This protocol provides a powerful tool to study the development of the meristem and floral organ primordia, and should be easily adaptable to many plant lineages, including other emerging model systems. It will allow researchers to explore questions outside the scope of common model systems.

Synthesis, toxicity evaluation and determination of possible mechanisms of antimicrobial effect of arabinogalactane-capped selenium nanoparticles

BACKGROUND

The elemental selenium nanoparticles (Se⁰NPs) find application in biology and medicine due to wide spectrum of their biological activity combined with low toxicity. For instance, Se⁰NPs are promising antimicrobial agents for plant treatment against the bacterial phytopathogen Clavibacter michiganensis sepedonicus (Cms). Careful characterization of possible mechanisms of antimicrobial action of Se⁰NPs as well as the assessment of their biosafety for plant and animal organisms represents urgent challenge.

METHODS

AG-stabilized Se⁰NPs (AG/Se⁰NPs) were synthesized by oxidation of selenide-anions by molecular oxygen dissolved in the reaction medium in the presence of AG macromolecules. The antimicrobial activity of AG/Se⁰NPs against Cms was investigated both by observing the change in optical density of bacterial suspension and directly evaluating the cell death using fluorescent microscopy with propidium iodide staining. The effect of AG/Se⁰NPs on the dehydrogenase activity was studied by determination of Cms enzymes ability to reduce colorless TTC to formazan. The effect of AG/Se⁰NPs nanocomposite on the respiration rate of Cms cells was examined by polarographic method. For qualitative visualization of the potential on the inner membrane of Cms mesosomes, the potential-dependent TMRM dye and fluorescence microscopy were used. The toxicity of the AG/Se⁰NPs was investigated on white mice by the Litchfield-Wilcoxon method. The effect of AG/Se⁰NPs on plant organisms (potato plants) was studied on healthy and Cms-infected plants by determining the level of chlorophyll and lipid peroxidation products (LPO) in their leaves when treated with nanoparticles.

RESULTS

Spherical Se° nanoparticles with an average size of 94 nm were obtained using the stabilizing potential of AG. It was found that these nanoparticles exhibited the pronounced (up to 60 %) bacteriostatic action (in 6.25 μg/mL concentration) against the bacterial phytopathogen Cms. It was shown and experimentally confirmed for the first time that the probable causes of the bacteriostatic action of AG/Se°NPs against Cms are non-reversible inhibition of Cms cell respiration, a decrease of the transmembrane potential with a change in the cell wall permeability for H⁺ protons and a decrease in their dehydrogenase activity. It was revealed that the treatment of healthy and Cms-infected potato plants with an aqueous solution of AG/Se°NPs involved no significant changes in the content of LPO and negative effect on the chlorophyll content, thus contributing to the saving of these values at the level of control intact plants.

CONCLUSION

Using a complex of complementary methods, we have found that antimicrobial activity of AG/Se⁰NPs is apparently due to their ability to inhibit the dehydrogenase activity of Cms cells, as well as to disrupt the integrity of the cell membrane, resulting in a decrease of transmembrane potential and reduction of cellular respiration. The antimicrobial and antibiofilm activity of AG/Se⁰NPs, together with their nontoxicity and safety for plant and animal organisms, determine the prospects for design of AG/Se⁰NPs-based drugs for the rehabilitation of plants from the Cms.

In situ laser manipulation of root tissues in transparent soil

AIMS

Laser micromanipulation such as dissection or optical trapping enables remote physical modification of the activity of tissues, cells and organelles. To date, applications of laser manipulation to plant roots grown in soil have been limited. Here, we show laser manipulation can be applied in situ when plant roots are grown in transparent soil.

METHODS

We have developed a Q-switched laser manipulation and imaging instrument to perform controlled dissection of roots and to study light-induced root growth responses. We performed a detailed characterisation of the properties of the cutting beams through the soil, studying dissection and optical ablation. Furthermore, we also studied the use of low light doses to control the root elongation rate of lettuce seedlings (Lactuca sativa) in air, agar, gel and transparent soil.

RESULTS

We show that whilst soil inhomogeneities affect the thickness and circularity of the beam, those distortions are not inherently limiting. The ability to induce changes in root elongation or complete dissection of microscopic regions of the root is robust to substrate heterogeneity and microscopy set up and is maintained following the limited distortions induced by the transparent soil environment.

CONCLUSIONS

Our findings show that controlled in situ laser dissection of root tissues is possible with a simple and low-cost optical set-up. We also show that, in the absence of dissection, a reduced laser light power density can provide reversible control of root growth, achieving a precise "point and shoot" method for root manipulation.