ABA promotes quiescence of the quiescent centre and suppresses stem cell differentiation in the Arabidopsis primary root meristem

Abstract

SUMMARYIt is well known that abscisic acid (ABA) can halt meristems for long periods without loss of meristem function, and can also promote root growth at low concentrations, but the mechanisms underlying such regulation are largely unknown. Here we show that ABA promotes stem cell maintenance in Arabidopsis root meristems by both promoting the quiescence of the quiescent centre (QC) and suppressing the differentiation of stem cells and their daughters. We demonstrate that these two mechanisms of regulation by ABA involve distinct pathways, and identify components in each pathway. Our findings demonstrate a cellular mechanism for a positive role for ABA in promoting root meristem maintenance and root growth in Arabidopsis.

Environmental Nitrate Stimulates Abscisic Acid Accumulation in Arabidopsis Root Tips by Releasing It from Inactive Stores

“…Immunofluorescence Reveals a Radial Pattern of ABA Localization in the Growing Root Tip ABA regulates root growth in response to environmental signals such as drought, salt stress, and nitrate, affecting meristem size and cell differentiation and triggering the induction of ABA-responsive gene expression (Signora et al, 2001;Sharp et al, 2004;Zhang et al, 2010;Duan et al, 2013;Geng et al, 2013). However, the spatial localization of ABA within the growing root tip is unknown.…”

Environmental nitrate signals through abscisic acid in the root tip

“…15,38,42,43 The internal location of ABA within the root may matter: nitrate-induced ABA accumulation occurs in the root tip, and intracellularly, rather than via the apoplast, as it is during exogenous ABA treatment. Although even exogenously added ABA ultimately accumulates in the endodermis, just as native ABA does, 33 it must pass through the epidermal and cortical cell layers to reach it.…”

“…Both ABA and nitrate control both cell division and cell elongation within the root tip. 14,15,[52][53][54] How do they intersect with these cellular controls? The GRAS transcription factor, SCARECROW (SCR), controls the stem cell niche in the root, thereby controlling the root's ability to produce new cells and drive further growth.…”

“…8 Although ABA is best known for controlling stomatal closure and seed dormancy, 13 it plays a major role in root development, regulating root elongation by modulating the major control points of root growth: cell division and cell elongation. 14,15 Additionally, ABA controls lateral root development by regulating initiation, emergence and meristem activation, as well as elongation (reviewed in 8 ). Because ABA mediates responses to many environmental signals, its ability to regulate lateral root formation provides the plant with the flexibility to modulate root architecture in response to a constantly varying environment.…”

The spatio-temporal specificity of PYR1/PYL/RCAR ABA receptors in response to developmental and environmental cues

“…17 Even in the belowground, ABA exerted a different role in regulating primary root growth and lateral root growth under osmotic stress conditions. [20][21][22] It is known ABA has a much stronger effect on lateral root than on the primary root, suggesting that different signaling mechanisms underlying regulating these two types of roots growth. 21 While PYL8 mediates the ability of ABA to inhibit primary root growth through the PP2C-SnRK2 pathway, 18 it together with PYL9 promotes lateral root growth recovery from inhibition independently of the core signaling pathway by enhancing MYB77-dependent transcription of auxin-responsive genes.…”