Abiotic Stress/Whole Plant Bio
Plant roots are the first organ to perceive water-deficit stress, but how the root system adapts to the unfavorable environment is still unclear. In rice, an intrinsically disordered protein with nearly 40% proline, REPETITIVE PROLINE-RICH PROTEIN (RePRP), is induced by water-deficit stress and abscisic acid (ABA) preferentially in the root elongation zone. Overexpression of RePRP confers a ‘short but heavy’ root phenotype, resembling the effect of water-deficit stress or ABA treatment; this phenotype is reduced in RePRP RNA-interference knockdown transgenic rice, which suggests that RePRP is sufficient and necessary for water-deficit stress- or ABA-repressed root development. Here we show that RePRP interacts with the highly ordered cytoskeleton components, actin and tubulin both in vivo and in vitro. The binding of RePRP reduces the abundance of actin filaments and impairs non-cellulosic polysaccharide transport to the cell wall. RePRP also reorients the microtubule network, which leads to disordered cellulose microfibril organization in the cell wall. The cell wall modification inhibits the elongation of root cells and promotes biomass accumulation in the ‘heavy’ root, which facilitates plant survival under adverse conditions. We demonstrate a novel role of intrinsically disordered proteins controlling cell expansion via an order-by-disorder mechanism for development of ‘short-but-heavy’ roots as an adaptive response to water deficit in rice.
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