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Review
. 2022 Apr 28:13:883363.
doi: 10.3389/fpls.2022.883363. eCollection 2022.

Cytoplasmic Linker Protein-Associating Protein at the Nexus of Hormone Signaling, Microtubule Organization, and the Transition From Division to Differentiation in Primary Roots

Laryssa Sophia Halat  1 , Breanne Bali  1 , Geoffrey Wasteneys  1
Affiliations
Review

Cytoplasmic Linker Protein-Associating Protein at the Nexus of Hormone Signaling, Microtubule Organization, and the Transition From Division to Differentiation in Primary Roots

Laryssa Sophia Halat et al. Front Plant Sci. .

Abstract

The transition from cell division to differentiation in primary roots is dependent on precise gradients of phytohormones, including auxin, cytokinins and brassinosteroids. The reorganization of microtubules also plays a key role in determining whether a cell will enter another round of mitosis or begin to rapidly elongate as the first step in terminal differentiation. In the last few years, progress has been made to establish connections between signaling pathways at distinct locations within the root. This review focuses on the different factors that influence whether a root cell remains in the division zone or transitions to elongation and differentiation using Arabidopsis thaliana as a model system. We highlight the role of the microtubule-associated protein CLASP as an intermediary between sustaining hormone signaling and controlling microtubule organization. We discuss new, innovative tools and methods, such as hormone sensors and computer modeling, that are allowing researchers to more accurately visualize the belowground growth dynamics of plants.

Keywords: Arabidopis thaliana; CLIP-associating protein (CLASP); PIN2; auxin; brassinosteroid (BR) signaling; cytokinin (CK); root apical meristem; sorting nexin 1 (SNX1).

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Hormone gradients define the developmental zones of the Arabidopsis root apical meristem. (A) Developmental zones of the root indicated in different colors. (B) The auxin signaling gradient in the root meristem. Auxin levels drop substantially at the beginning of the transition zone, forming an auxin minimum before increasing again toward the elongation zone. (C) The BR signaling gradient increases at the transition zone in the root meristem. The heatmaps in B) and C) denote levels of hormone (auxin) and signaling (BR).
FIGURE 2
FIGURE 2
CLASP localization and microtubule organization in interphase cells in the root meristem. In the division zone of wild-type (WT) RAMs (lower left), CLASP (green) distributes to the sharp transverse edges (blue) formed from recent cell divisions. This promotes the formation of TFBs, allowing microtubules (pink) to grow around these edges. In the elongation zone of WT roots (upper left), CLASP localizes to the longitudinal edges (purple) and a primarily transverse array of microtubules forms respective to the axis of growth. In the division zone of plants with CLASP downregulated (WT + BR, bzr1-1d) or absent (clasp-1) (right), the lack of CLASP causes microtubules to adopt a primarily transverse array, which is associated with precocious cell cycle exit. This leads to a smaller meristem as marked by an earlier transition zone (dotted line on root) when compared to the WT.
FIGURE 3
FIGURE 3
Signaling pathways that converge in the regulation of root apical meristem growth.
See this image and copyright information in PMC

References

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