Abstract
Plant roots fulfill important functions as they serve in water and nutrient uptake, provide anchorage of the plant body in the soil and in some species form the site of symbiotic interactions with soil-living biota. Root hairs, tubular-shaped outgrowths of specific epidermal cells, significantly increase the root’s surface area and aid in these processes. In this review we focus on the molecular mechanisms that determine the hair and non-hair cell fate of epidermal cells and that define the site on the epidermal cell where the root hair will be initiated (=planar polarity determination). In the model plant Arabidopsis, trichoblast and atrichoblast cell fate results from intra- and intercellular position-dependent signaling and from complex feedback loops that ultimately regulate GL2 expressing and non-expressing cells. When epidermal cells reach the end of the root expansion zone, root hair promoting transcription factors dictate the establishment of polarity within epidermal cells followed by the selection of the root hair initiation site at the more basal part of the trichoblast. Molecular players in the abovementioned processes as well as the role of phytohormones are discussed, and open areas for future experiments are identified.
Highlights
Reviewed by: Rishi Bhalerao, Sveriges Lantbruksuniversitet, Sweden Myeong Min Lee, Yonsei University, South Korea Su-Hwan Kwak, Long Island University, USA
In this review we focus on the molecular mechanisms that determine the hair and non-hair cell fate of epidermal cells and that define the site on the epidermal cell where the root hair will be initiated (=planar polarity determination)
When epidermal cells reach the end of the root expansion zone, root hair promoting transcription factors dictate the establishment of polarity within epidermal cells followed by the selection of the root hair initiation site at the more basal part of the trichoblast
Summary
Plant roots fulfill important functions and help to maximize survival and adaptation of plants to continuously changing environments. They serve in water and nutrient uptake, provide anchorage of the plant body in the soil and in some species form the site of symbiotic interactions with soilliving biota. The root body consists of many different cell types that all originate from the meristem and that all pass through consecutive phases of cellular activities before developing specialized functions and reaching maturity. In the meristematic zone cells undergo mitotic divisions. As such, this zone mainly determines the root’s cell number. Parallel deposition of cellulose microfibrils, transverse to the future long axis of the cell creates anisotropic cell wall mechanics that accommodate longitudinal cell expansion (Anderson et al, 2010)
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