Intercellular communication during plant development

Abstract

Multicellular organisms depend on cell-to-cell communication to coordinate both development and environmental responses across diverse cell types. Intercellular signaling is particularly critical in plants because development is primarily postembryonic and continuous over a plant's life span. Additionally, development is impacted by restrictions imposed by a sessile lifestyle and limitations on relative cell positions. Many non-cell-autonomous signaling mechanisms are known to function in plant development, including those involving receptor kinases, small peptides, and mobile transcription factors. In this review, we focus on recent findings that highlight novel mechanisms in intercellular signaling during development. New details of small RNA movement, including microRNA movement, are discussed, as well as protein movement and distribution of reactive oxygen species (ROS) in ROS signaling. Finally, a novel temporal mechanism for lateral root positioning and the implications for intercellular signaling are considered.

Figure 1.

Schematic of Cell Types in the Arabidopsis Root Tip. (A) Transverse section. (B) Median longitudinal section.

Figure 2.

Schematic of the Expression of miR165/166 and PHB mRNA and Their Activity Zone. (A) miR165/166 is expressed in the endodermis (dark blue) but moves outward to neighboring cell types (lighter blue). (B) PHB mRNA is highly expressed in the metaxylem (red) and inner vascular cells (orange) and has lower expression in the outer vascular cells and endodermis (dark and lighter yellow, respectively). (C) miR165/166 represses PHB mRNA in the activity zone (green), allowing PHB protein to specify metaxylem (dark pink). Note that PHB protein is found throughout the inner vascular cells (light pink) as well and presumably has other functions.

Figure 3.

Wave of Gene Expression in the Oscillation Zone Establishes the Prepattern for LR Formation. (A) Schematic of the Arabidopsis root tip, median longitudinal section in the xylem axis with each of the developmental zones: merstematic (MZ), elongation (EZ), and differentiation zones (DZ). (B) Schematic of a wave of gene expression in the oscillation zone over time. (C) The oscillation of DR5 is observed in the protoxylem; however, LRs develop from the pericycle. Thus, the outcome of the oscillation in the protoxylem (light purple with blue edge) may be signaled outward to the adjacent pericycle cells (blue-to-orange gradient).