Altered Root Growth, Auxin Metabolism and Distribution in Arabidopsis thaliana Exposed to Salt and Osmotic Stress

Abstract

Salt and osmotic stress are the main abiotic stress factors affecting plant root growth and architecture. We investigated the effect of salt (100 mM NaCl) and osmotic (200 mM mannitol) stress on the auxin metabolome by UHPLC-MS/MS, auxin distribution by confocal microscopy, and transcript levels of selected genes by qRT-PCR in Arabidopsis thaliana ecotype Columbia-0 (Col-0) and DR5rev::GFP (DR5) line. During long-term stress (13 days), a stability of the auxin metabolome and a tendency to increase indole-3-acetic acid (IAA) were observed, especially during salt stress. Short-term stress (3 h) caused significant changes in the auxin metabolome, especially NaCl treatment resulted in a significant reduction of IAA. The data derived from auxin profiling were consistent with gene expressions showing the most striking changes in the transcripts of YUC, GH3, and UGT transcripts, suggesting disruption of auxin biosynthesis, but especially in the processes of amide and ester conjugation. These data were consistent with the auxin distribution observed in the DR5 line. Moreover, NaCl treatment caused a redistribution of auxin signals from the quiescent center and the inner layers of the root cap to the epidermal and cortical cells of the root elongation zone. The distribution of PIN proteins was also disrupted by salt stress; in particular, PIN2 was suppressed, even after 5 min of treatment. Based on our results, the DR5 line was more sensitive to the applied stresses than Col-0, although both lines showed similar trends in root morphology, as well as transcriptome and metabolome parameters under stress conditions.

Inactivation of the entire Arabidopsis group II GH3s confers tolerance to salinity and water deficit

“…Salinity is well known to cause general arrest in plant growth (Zhao et al ., 2020), and a decreased length of the primary root in salt‐stressed Arabidopsis plants is documented (Smolko et al ., 2021). Thus, we used the growth of the primary root as an indicator of the tolerance to salinity stress.…”

Beneficial Microbes and Molecules for Mitigation of Soil Salinity in Brassica Species: A Review

“…The plant hormone auxin, which controls root development and architecture, plays an important role in root response to salt stress. Root growth inhibited by salt has been shown to be associated with a significant reduction in IAA during short-term stress [58]. The auxin metabolome was consistent with gene expressions, with the most striking changes observed in the transcripts of YUC (YUCCA flavin monooxygenases), GH3 (auxin amidosynthetases), and UGT (uridine diphosphate glycosyltransferase) genes, suggesting a disruption of auxin biosynthesis, but particularly in the processes of amide and ester conjugation.…”

“…The auxin metabolome was consistent with gene expressions, with the most striking changes observed in the transcripts of YUC (YUCCA flavin monooxygenases), GH3 (auxin amidosynthetases), and UGT (uridine diphosphate glycosyltransferase) genes, suggesting a disruption of auxin biosynthesis, but particularly in the processes of amide and ester conjugation. In addition to metabolism, polar auxin transport has also been shown to be involved in reduced auxin accumulation in the root during salt stress [58][59][60]. Under salt stress, IAA showed a tendency to increase in B. rapa seedlings [61].…”

New Insights Into the Activity of Apple Dihydrochalcone Phloretin: Disturbance of Auxin Homeostasis as Physiological Basis of Phloretin Phytotoxic Action

“…Some studies have reported that environmental factors, such as salt and osmotic stresses, affect not only IAA levels, but even more the quantities of its precursors, conjugates and degradation products ( Pavlović et al, 2018 ; Smolko et al, 2021 ). Our results indicated a decrease in the content of all auxin precursors except IAM in the root and particularly pronounced reduction in IAN levels shortly after phloretin treatment.…”