Agriculture Reference
In-Depth Information
9
Lessons from leaf epidermal patterning in plants
Bhylahalli Purushottam Srinivas and Martin H ulskamp
9.1
Overview
The epidermis of mature leaves consists of three different types of cells. Most cells
differentiate into normal epidermal pavement cells. Additionally, trichomes and
stomata are found non-randomly distributed on the surface. The establishment of
such distribution patterns involves different kinds of cell-to-cell communication.
While trichome patterning appears to be primarily mediated by the movement of
transcription factors through plasmodesmata, stomatal patterning seems to involve
receptor-ligand-based cellular communication. This review compares the mecha-
nisms of the two patterning systems.
9.2
Introduction
During plant development, all cells become successively restricted in their devel-
opmental potential and eventually adopt a distinct cell fate and differentiate ac-
cordingly. The spatial coordination of cell fate determination is mostly based on
cell-to-cell communication, which may occur either over long distances (for exam-
ple by hormones) or locally between neighbouring cells.
Most of our current knowledge on the cellular communication occurring dur-
ing epidermal differentiation is derived from genetic analysis in the model plant
Arabidopsis
. Here, one of the best-studied models for analysing the mechanisms of
cellular communication in the context of developmental processes is the leaf epider-
mis. Several aspects facilitate its analysis. On the one hand, the epidermis is readily
accessible for visual inspection and experimental manipulations. On the other hand,
the epidermis consists of only a few cell types that show a certain spacing or dis-
tribution pattern. Both trichomes as well as stomata are distributed non-randomly
between epidermal pavement cells, suggesting the existence of mechanisms that reg-
ulate this pattern. The current data suggest that these mechanisms are fundamentally
different for trichomes and stomata. The goal of this review is to compare these two
patterning systems, with emphasis on the communication between epidermal cells.
9.3
Mechanisms of trichome patterning
Trichomes are found on the aerial surface of most higher plants and are important
for the protection of the plant against insects and UV radiation and the reduction
