Natural Root Cellular Variation in Responses to Osmotic Stress in Arabidopsis thaliana Accessions

Abstract

Arabidopsis naturally occurring populations have allowed for the identification of considerable genetic variation remodeled by adaptation to different environments and stress conditions. Water is a key resource that limits plant growth, and its availability is initially sensed by root tissues. The root's ability to adjust its physiology and morphology under water deficit makes this organ a useful model to understand how plants respond to water stress. Here, we used hyperosmotic shock stress treatments in different Arabidopsis accessions to analyze the root cell morphological responses. We found that osmotic stress conditions reduced root growth and root apical meristem (RAM) size, promoting premature cell differentiation without affecting the stem cell niche morphology. This phenotype was accompanied by a cluster of small epidermal and cortex cells with radial expansion and root hairs at the transition to the elongation zone. We also found this radial expansion with root hairs when plants are grown under hypoosmotic conditions. Finally, root growth was less affected by osmotic stress in the Sg-2 accession followed by Ws, Cvi-0, and Col-0; however, after a strong osmotic stress, Sg-2 and Cvi-0 were the most resilience accessions. The sensitivity differences among these accessions were not explained by stress-related gene expression. This work provides new cellular insights on the Arabidopsis root phenotypic variability and plasticity to osmotic stress.Genes 2019, 10, 983 2 of 23 northern hemisphere and consequently is subjected to diverse environmental conditions, generating different natural variants called accessions [1]. The Arabidopsis accessions are an important genetic resource to identify mechanisms underlying plant development and stress tolerance as plant genotypes are constantly shaped by biotic and abiotic factors [2]. These phenotypic and genetic variations have enabled the characterization of responses in Arabidopsis natural variants using a range of different approaches [3][4][5][6][7][8].Water deficit is an abiotic stress that affects plant development and productivity. Water availability can be altered by changes in solute concentration (i.e., sugars, salt, inorganic cations and anions) during drought, cold stress, and freezing [9,10]. Some phenotypic and genetic analyses have identified tolerant accessions that can be useful to study the traits related to water deficit tolerance [11,12] (for a review see [13]).Although stress affects the whole organism [14-17], leaves and roots display different responses in order to reduce water loss and promote water foraging for survival [18]. Accordingly, plant roots act on the frontlines by sensing the water deficit, adjusting osmotic homeostasis, forcing water entrance, and avoiding water loss through the accumulation of compatible solutes inside the tissues [19,20]. This rapid root response allows increased water uptake to maintain cellular turgor and reduce the negative effects in the leaves; however, when the stress becomes more severe, the growth in all ...

Root vacuolar sequestration and suberization contribute to salinity tolerance in Pistacia spp. rootstocks

“…The development of the apoplastic barriers is highly responsive to abiotic stress (Enstone et al, 2003;Barberon, 2017;Byrt et al, 2018;Chen et al, 2018;Kreszies et al, 2019;Wang et al, 2020), and contributes in salinity tolerance (Chen et al, 2018;Wang et al, 2020). The root meristematic zone, in particular, represents a region with the highest plasticity (Rost, 2011) that differentiates earlier under abiotic stress (Ji et al, 2014;Cajero-Sanchez et al, 2019). Our result suggests that both the timing of apoplastic barrier differentiation and the increase of suberin deposition contributed to the increase in suberization under salt stress.…”

“…In order to investigate the mechanism of salt tolerance, we visualized the cellular localization of sodium ions in live root sections with CoroNa Green, an indicator that exhibits an increase in green fluorescence emission intensity upon Na+ binding (Park et al, 2009;Gonzalez et al, 2012). Root developmental signals have several control points, and biotic stress has been shown to induce root differentiation closer to the apical meristem (Rost, 2011;Cajero-Sanchez et al, 2019). To assess the relationship between root maturity and salinity tolerance responses, Na + localization was analyzed across a root developmental gradient, staged by type and extent of xylem formation (Fig 3a, b, Supp.…”

The Arabidopsis TETRATRICOPEPTIDE THIOREDOXIN-LIKE 1 Gene Is Involved in Anisotropic Root Growth during Osmotic Stress Adaptation

“…At the cellular level, growth is regulated by turgor pressure and the rate of cell wall loosening. Under hyperosmotic stress, root epidermal and cortex cells swell [23] similar to that observed with genetic or chemical disruption of cell wall organization [24][25][26][27][28]. Likewise, mutants impaired in cell wall organization/integrity are hypersensitive to osmotic/ionic stress [22,29,30].…”

“…Likewise, mutants impaired in cell wall organization/integrity are hypersensitive to osmotic/ionic stress [22,29,30]. At the organ level, hyperosmotic stress inhibits root cell proliferation and elongation [23].…”

Interplay between Hormones and Several Abiotic Stress Conditions on Arabidopsis thaliana Primary Root Development

“…Under salt stress conditions, the PR initial growth reduction is due to the osmotic pressure of the salt and later is caused by the inability of the roots to contend with the toxic effect of the ions [103]. Under both osmotic and salt stress conditions, the meristem cell number and the length of the completely elongated cells are affected [95,104,105]. In addition, many studies have shown that ABA concentration increases during drought stress and helps to withstand PR growth under low water availability conditions [95,[105][106][107][108].…”