Live Imaging of Arabidopsis Leaf and Vegetative Meristem Development

Live imaging of Arabidopsis shoot primordia via a confocal laser scanning microscope

Live imaging through confocal laser scanning microscopy enables the recording, analysis, and comparison of the dynamics of shapes and gene expression patterns of plant shoot apical meristems (SAMs) or primordia. Here, we provide a protocol to describe the preparation process of imaging Arabidopsis SAMs and primordia using a confocal microscope. We describe steps for dissection, visualization of meristems using dyes and fluorescent proteins, and gain 3D morphology of meristems. We then detail analysis of shoot meristems using time-lapse imaging. For complete details on the use and execution of this protocol, please refer to Peng et al. (2022).¹.

An optimized pipeline for live imaging whole Arabidopsis leaves at cellular resolution

BACKGROUND

Live imaging is the gold standard for determining how cells give rise to organs. However, tracking many cells across whole organs over large developmental time windows is extremely challenging. In this work, we provide a comparably simple method for confocal live imaging entire Arabidopsis thaliana first leaves across early development. Our imaging method works for both wild-type leaves and the complex curved leaves of the jaw-1D mutant.

RESULTS

We find that dissecting the cotyledons, affixing a coverslip above the samples and mounting samples with perfluorodecalin yields optimal imaging series for robust cellular and organ level analysis. We provide details of our complementary image processing steps in MorphoGraphX software for segmenting, tracking lineages, and measuring a suite of cellular properties. We also provide MorphoGraphX image processing scripts we developed to automate analysis of segmented images and data presentation.

CONCLUSIONS

Our imaging techniques and processing steps combine into a robust imaging pipeline. With this pipeline we are able to examine important nuances in the cellular growth and differentiation of jaw-D versus WT leaves that have not been demonstrated before. Our pipeline is approachable and easy to use for leaf development live imaging.

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.

Confocal Imaging of Developing Leaves

Questions in developmental biology are most frequently addressed by using fluorescent markers of otherwise invisible cell states. In plants, such questions can be addressed most conveniently in leaves. Indeed, from the formation of stomata and trichomes within the leaf epidermis to that of vein networks deep into the leaf inner tissue, leaf cells and tissues differentiate anew during the development of each leaf. Moreover, leaves are produced in abundance and are easily accessible to visualization and perturbation. Yet a detailed procedure for the perturbation, dissection, mounting, and imaging of developing leaves has not been described. Here we address this limitation (1) by providing robust, step-by-step protocols for the local application of the plant hormone auxin to developing leaves and for the routine dissection and mounting of leaves and leaf primordia, and (2) by offering practical guidelines for the optimization of imaging parameters for confocal microscopy. We describe the procedure for the first leaves of Arabidopsis, but the same approach can be easily applied to other leaves of Arabidopsis or to leaves of other plants. © 2022 Wiley Periodicals LLC. Support Protocol 1: Preparation of plant growth medium Support Protocol 2: Preparation of growth medium plates Basic Protocol 1: Seed sterilization, sowing, and germination, and seedling growth Support Protocol 3: Preparation of IAA-lanolin paste Basic Protocol 2: Application of IAA-lanolin paste to 3.5-DAG first leaves Basic Protocol 3: Dissection of 3- to 6-DAG first leaves and leaf primordia Basic Protocol 4: Dissection of 1- and 2-DAG first-leaf primordia Basic Protocol 5: Mounting of dissected leaves and leaf primordia Support Protocol 4: Quality check of mounted leaves and leaf primordia by fluorescence microscopy Basic Protocol 6: Imaging of mounted leaves and leaf primordia by confocal microscopy.