A Genetic Regulatory Network in the Development of Trichomes and Root Hairs

Abstract

Trichomes and root hairs differentiate from epidermal cells in the aerial tissues and roots, respectively. Because trichomes and root hairs are easily accessible, particularly in the model plant Arabidopsis, their development has become a well-studied model of cell differentiation and growth. Molecular genetic analyses using Arabidopsis mutants have demonstrated that the differentiation of trichomes and root hair/hairless cells is regulated by similar molecular mechanisms. Transcriptional complexes regulate differentiation into trichome cells and root hairless cells, and formation of the transcriptional complexes is inhibited in neighboring cells. Control of cell growth after fate determination has also been analyzed using Arabidopsis mutants. The progression of endoreduplication cycles, reorientation of microtubules, and organization of the actin cytoskeleton play important roles in trichome growth. Various cellular components such as ion channels, the actin cytoskeleton, microtubules and cell wall materials, and intracellular signal transduction act to establish and maintain root hair tip growth.

Disruption of the 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) gene results in albino, dwarf and defects in trichome initiation and stomata closure in Arabidopsis

“…When 10 µM GA 3 was applied, the transcript levels of GL1, TTG1, and SPY significantly increased or decreased, in a tendency opposite to that in dxr mutant (Figure 7). This result is consistent with the important role of GAs in trichome formation and development [43][44][45].…”

“…In addition to the albino phenotype, we also found trichome initiation and stomata closure defects as a result of DXR disruption. It was previously reported that GAs play important roles in trichome development by regulating trichome-associated genes including GL1, GL3, and SPY [41][42][43][44][45]. As GAs are a class of important products derived from MEP-related isoprenoid biosynthetic pathways, it is reasonable to link DXR disruption to the observed trichome developmental defects.…”

Haustorial Hairs Are Specialized Root Hairs That Support Parasitism in the Facultative Parasitic Plant Phtheirospermum japonicum

“…Root hairs are tubular outgrowths of epidermis cells. They absorb water and nutrients, interact with microorganisms, and anchor the plant to the soil (Ishida et al, 2008). Using Arabidopsis (Arabidopsis thaliana) as a model, the genetics and molecular mechanisms of root hair formation have been studied extensively.…”

“…The root hairs develop in the differentiation zone of the root (Petricka et al, 2012). In Arabidopsis, the root epidermis layer consists of nonhair and hair cells, and their differentiation is tightly controlled by defined transcriptional complexes (Ishida et al, 2008). The polar growth of root hairs involves Ca 2+ and ROS signals, which are required for the maintenance of cell wall integrity at the tip of growing root hairs (Datta et al, 2011).…”

Root hair formation at the root-hypocotyl junction in CPC-LIKE MYB double and triple mutants ofArabidopsis

“…1,4,9,11,25 The TTG1-GL3/ EGL3-WER transcriptional complex promotes GL2 expression to induce a hairless cell differentiation. 26,27 CPC disrupts this transcriptional complex by competing with WER, thus negatively regulating the expression of GL2 and resulting in root hair formation. 28 In addition to the root hair formation in the major portion of the root, CPC family genes are also involved in root hair formation at the root-hypocotyl junction.…”