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.
Highlights
Phenotypic plasticity is an important property that allows plants to respond to a wide range of different environments
In our study we showed that the decrease in size of the root apical meristem (RAM) is related to a premature transit in two points: the proliferation domain to the transition domain, as the number of cells in the proliferation domain changes under osmotic stress treatments as compared to our control treatment; and the transition domain to the elongation zone, as the cell size in the former is shorter in almost all the accessions tested
In this study we showed that, in all the Arabidopsis accessions used, the primary root growth diminished under stress conditions
Summary
Phenotypic plasticity is an important property that allows plants to respond to a wide range of different environments. 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]. 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])
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