Effective root responses to salinity stress include maintained cell expansion and carbon allocation

Abstract

Acclimation of root growth is vital for plants to survive salt stress. Halophytes are great examples of plants that thrive under high salt concentrations but their salt tolerance mechanisms, especially those mediated by root responses, are still largely unknown. We compared root growth responses of the halophyte Schrenkiella parvula with its glycophytic relative species Arabidopsis thaliana under salt stress, and performed root transcriptomic analysis to identify differences in gene regulatory networks underlying their physiological responses. Primary root growth of S. parvula is less sensitive to salt compared with Arabidopsis. The root transcriptomic analysis of S. parvula revealed the induction of sugar transporters and genes regulating cell expansion and suberization under salt stress. 14C-labelled carbon partitioning analyses consistently showed that S. parvula had a higher incorporation rate of soluble sugars in roots under salt stress compared to Arabidopsis. Further physiological investigation revealed that S. parvula roots do not show a halotropic response and maintain root cell expansion and enhanced suberization even under severe salt stress. In summary, our study demonstrates that roots of S. parvula deploy multiple physiological and developmental adjustments under salt stress to maintain growth, providing new avenues to improve salt tolerance of plants using root-specific strategies.

Genome-wide analysis of annexin gene family in Schrenkiella parvula and Eutrema salsugineum suggests their roles in salt stress response

“…Analysis of candidate gene expression ( SpAnn 1, 2, and 6) in root of S . parvula was retrieved from Li et al [ 39 ] ( S7 Table ) research. Based on the results, SpAnn6 showed the greatest difference in 3 h after salt treatment.…”

“…salsugineum seedlings which were treated with 300 mM NaCl and collected after 24 h [ 38 ] while in S . parvula’ s seedlings treated with 175 mM NaCl and collected after 3 h, 24 h, 48 h [ 39 ], candidate genes (Ann1,2 and 6) showed weak expression changes (range from -0.447 to +0.496). These differences in expressions could be attributed to the difference in NaCl concentration (175mM vs 300mM) and different seedling growth phase (4 days vs 30days after germination) in two halophytes.…”

“…The expression data for candidate Ann genes in S . parvula ’s root were acquired from Li et al study [ 39 ]. The heatmap was performed using the GraphPad Prism v9.…”

“…The expression data for Ann genes in E. salsugineum was retrieved from the public Short Read Archive (SRA) (SRP323931 and SRP135727) of NCBI to explore their levels of expression [38]. The expression data for candidate Ann genes in S. parvula's root were acquired from Li et al study [39]. The heatmap was performed using the GraphPad Prism v9.…”

“…SpAnn6 gene expression was significantly increased 3 h after salt stress (with 2.13 relative expression level) compared to 6 h and 12 h (Fig 8). Analysis of candidate gene expression (SpAnn1, 2, and 6) in root of S. parvula was retrieved from Li et al [39] (S7 Table ) research. Based on the results, SpAnn6 showed the greatest difference in 3 h after salt treatment.…”