Abstract
The arabinogalactan proteins (AGPs) are involved in a range of plant processes, including cell differentiation and expansion. Here, barley root hair mutants and their wild-type parent cultivars were used, as a model system, to reveal the role of AGPs in root hair development. The treatment of roots with different concentrations of βGlcY (a reagent which binds to all classes of AGPs) inhibited or totally suppressed the development of root hairs in all of the cultivars. Three groups of AGP (recognized by the monoclonal antibodies LM2, LM14, and MAC207) were diversely localized in trichoblasts and atrichoblasts of root hair-producing plants. The relevant epitopes were present in wild-type trichoblast cell walls and cytoplasm, whereas in wild-type atrichoblasts and in all epidermal cells of a root hairless mutant, they were only present in the cytoplasm. In all of cultivars the higher expression of LM2, LM14, and MAC207 was observed in trichoblasts at an early stage of development. Additionally, the LM2 epitope was detected on the surface of primordia and root hair tubes in plants able to generate root hairs. The major conclusion was that the AGPs recognized by LM2, LM14, and MAC207 are involved in the differentiation of barley root epidermal cells, thereby implying a requirement for these AGPs for root hair development in barley.
Highlights
The arabinogalactan proteins (AGPs) are a large heterogeneous family of hydroxyproline-rich glycoproteins found both within and on the surface of plant cells (Fincher et al, 1983; Nguema-Ona et al, 2012), and in representatives of the entire plant kingdom, including mosses (Lee et al, 2005)
The relevant epitopes were present in wild-type trichoblast cell walls and cytoplasm, whereas in wild-type atrichoblasts and in all epidermal cells of a root hairless mutant, they were only present in the cytoplasm
The major conclusion was that the AGPs recognized by LM2, LM14, and MAC207 are involved in the differentiation of barley root epidermal cells, thereby implying a requirement for these AGPs for root hair development in barley
Summary
The arabinogalactan proteins (AGPs) are a large heterogeneous family of hydroxyproline-rich glycoproteins found both within and on the surface of plant cells (Fincher et al, 1983; Nguema-Ona et al, 2012), and in representatives of the entire plant kingdom, including mosses (Lee et al, 2005). Other AGPs are secreted into either the intercellular space (Samaj et al, 2000) or to the plant’s exterior in the form of mucilage (Moody et al, 1988) Their molecular size can vary from 60 to 300 kDa, they all consist of a short peptide core surrounded by carbohydrate moieties which comprise at least 90% of the molecule’s mass (Serpe and Nothnagel, 1999). The glycan part consists of sugars (arabinose, galactose, rhamnose, fucose, glucuronic acid, and xylose) (Nothnagel, 1997; Showalter, 2001) generating a carbohydrate moiety which varies greatly both between species, and even between organs of a given
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