Cellular requirements for PIN polar cargo clustering in Arabidopsis thaliana.

Cell and tissue polarization is fundamental for plant growth and morphogenesis. The polar, cellular localization of Arabidopsis PIN-FORMED (PIN) proteins is crucial for their function in directional auxin transport. The clustering of PIN polar cargoes within the plasma membrane has been proposed to be important for the maintenance of their polar distribution.

Early developmental plasticity of lateral roots in response to asymmetric water availability.

Root branching is influenced by the soil environment and exhibits a high level of plasticity. We report that the radial positioning of emerging lateral roots is influenced by their hydrological environment during early developmental stages. New lateral root primordia have both a high degree of flexibility in terms of initiation and development angle towards the available water.

Lateral Root Formation in Arabidopsis: A Well-Ordered LRexit.

Lateral roots (LRs) are crucial for increasing the surface area of root systems to explore heterogeneous soil environments. Major advances have recently been made in the model plant arabidopsis (Arabidopsis thaliana) to elucidate the cellular basis of LR development and the underlying gene regulatory networks (GRNs) that control the morphogenesis of the new root organ. This has provided a foundation for understanding the sophisticated adaptive mechanisms that regulate how plants pattern their root branching to match the spatial availability of resources such as water and nutrients in their external environment.

Root branching toward water involves posttranslational modification of transcription factor ARF7.

Plants adapt to heterogeneous soil conditions by altering their root architecture. For example, roots branch when in contact with water by using the hydropatterning response. We report that hydropatterning is dependent on auxin response factor ARF7.

Multiscale imaging of plant development by light-sheet fluorescence microscopy.

Light-sheet fluorescence microscopy (LSFM) methods collectively represent the major breakthrough in developmental bio-imaging of living multicellular organisms. They are becoming a mainstream approach through the development of both commercial and custom-made LSFM platforms that are adjusted to diverse biological applications. Based on high-speed acquisition rates under conditions of low light exposure and minimal photo-damage of the biological sample, these methods provide ideal means for long-term and in-depth data acquisition during organ imaging at single-cell resolution.

The dynamics of root cap sloughing in Arabidopsis is regulated by peptide signalling.

The root cap protects the stem cell niche of angiosperm roots from damage. In Arabidopsis, lateral root cap (LRC) cells covering the meristematic zone are regularly lost through programmed cell death, while the outermost layer of the root cap covering the tip is repeatedly sloughed. Efficient coordination with stem cells producing new layers is needed to maintain a constant size of the cap.

Cellular Patterning of Roots Under Low Phosphate Conditions.

Phosphorus is a crucial macronutrient for plants playing a critical role in many cellular signaling and energy cycling processes. In light of this, phosphorus acquisition efficiency is an important target trait for crop improvement, but it also provides an ecological adaptation for growth of plants in low nutrient environments. Increased root hair density has been shown to improve phosphorus uptake and plant health in a number of species.

Adding a Piece to the Leaf Epidermal Cell Shape Puzzle.

The jigsaw puzzle-shaped pavement cells in the leaf epidermis collectively function as a load-bearing tissue that controls organ growth. In this issue of Developmental Cell, Majda et al. (2017) shed light on how the jigsaw shape can arise from localized variations in wall stiffness between adjacent epidermal cells.

Shaping 3D Root System Architecture.

Plants are sessile organisms rooted in one place. The soil resources that plants require are often distributed in a highly heterogeneous pattern. To aid foraging, plants have evolved roots whose growth and development are highly responsive to soil signals.

Live tracking of moving samples in confocal microscopy for vertically grown roots.

Roots navigate through soil integrating environmental signals to orient their growth. The root is a widely used model for developmental, physiological and cell biological studies. Live imaging greatly aids these efforts, but the horizontal sample position and continuous root tip displacement present significant difficulties.

Plant Biology: Building Barriers… in Roots.

The Casparian strip is an important barrier regulating water and nutrient uptake into root tissues. New research reveals two peptide signals and their co-receptors play critical roles patterning and maintaining barrier integrity.

Light Sheet Fluorescence Microscopy of Plant Roots Growing on the Surface of a Gel.

One of the key questions in understanding plant development is how single cells behave in a larger context of the tissue. Therefore, it requires the observation of the whole organ with a high spatial- as well as temporal resolution over prolonged periods of time, which may cause photo-toxic effects. This protocol shows a plant sample preparation method for light-sheet microscopy, which is characterized by mounting the plant vertically on the surface of a gel.

Endosomal Interactions during Root Hair Growth.

The dynamic localization of endosomal compartments labeled with targeted fluorescent protein tags is routinely followed by time lapse fluorescence microscopy approaches and single particle tracking algorithms. In this way trajectories of individual endosomes can be mapped and linked to physiological processes as cell growth. However, other aspects of dynamic behavior including endosomal interactions are difficult to follow in this manner.

Rules and Self-Organizing Properties of Post-embryonic Plant Organ Cell Division Patterns.

Plants form new organs with patterned tissue organization throughout their lifespan. It is unknown whether this robust post-embryonic organ formation results from stereotypic dynamic processes, in which the arrangement of cells follows rigid rules. Here, we combine modeling with empirical observations of whole-organ development to identify the principles governing lateral root formation in Arabidopsis.

Trans-Golgi network localized small GTPase RabA1d is involved in cell plate formation and oscillatory root hair growth.

Background: Small Rab GTPases are important regulators of vesicular trafficking in plants. AtRabA1d, a member of the RabA1 subfamily of small GTPases, was previously found in the vesicle-rich apical dome of growing root hairs suggesting a role during tip growth; however, its specific intracellular localization and role in plants has not been well described.

Results: The transient expression of 35S::GFP:RabA1d construct in Allium porrum and Nicotiana benthamiana revealed vesicular structures, which were further corroborated in stable transformed Arabidopsis thaliana plants.

A spatial accommodation by neighboring cells is required for organ initiation in Arabidopsis.

Lateral root formation in plants can be studied as the process of interaction between chemical signals and physical forces during development. Lateral root primordia grow through overlying cell layers that must accommodate this incursion. Here, we analyze responses of the endodermis, the immediate neighbor to an initiating lateral root.

Live imaging of Arabidopsis development.

Live cell imaging is an essential methodology for studying the structure, dynamics, and functions of cells in a living plant under normal or stressed growth conditions. Arabidopsis thaliana is perfectly amenable to various live microscopy techniques. In this chapter, we provide guidelines to design live-imaging experiments.

An auxin transport mechanism restricts positive orthogravitropism in lateral roots.

As soon as a seed germinates, plant growth relates to gravity to ensure that the root penetrates the soil and the shoot expands aerially. Whereas mechanisms of positive and negative orthogravitropism of primary roots and shoots are relatively well understood, lateral organs often show more complex growth behavior. Lateral roots (LRs) seemingly suppress positive gravitropic growth and show a defined gravitropic set-point angle (GSA) that allows radial expansion of the root system (plagiotropism).

Lateral root morphogenesis is dependent on the mechanical properties of the overlaying tissues.

In Arabidopsis, lateral root primordia (LRPs) originate from pericycle cells located deep within the parental root and have to emerge through endodermal, cortical, and epidermal tissues. These overlaying tissues place biomechanical constraints on the LRPs that are likely to impact their morphogenesis. This study probes the interplay between the patterns of cell division, organ shape, and overlaying tissues on LRP morphogenesis by exploiting recent advances in live plant cell imaging and image analysis.

Probing and tracking organelles in living plant cells.

Intracellular organelle movements and positioning play pivotal roles in enabling plants to proliferate life efficiently and to survive diverse environmental stresses. The elaborate dissection of organelle dynamics and their underlying mechanisms (e.g.

High-resolution live imaging of plant growth in near physiological bright conditions using light sheet fluorescence microscopy.

Most plant growth occurs post-embryonically and is characterized by the constant and iterative formation of new organs. Non-invasive time-resolved imaging of intact, fully functional organisms allows studies of the dynamics involved in shaping complex organisms. Conventional and confocal fluorescence microscopy suffer from limitations when whole living organisms are imaged at single-cell resolution.