Title : Hormonal dynamic during salt stress response of salt-sensitive Arabidopsis thaliana and salt-tolerant Thellungiella salsuginea.
Abstract:
Salinization represents a serious problem of modern agriculture. Elucidation of the tolerance mechanisms is highly desirable. Phytohormones play an important role in stress responses as well as in regulation of plant growth and development. In our study, we focused on the impact of salinity on hormonal dynamics. Salt stress responses of salt-sensitive Arabidopsis thaliana and its close relative, salt-tolerant Thellungiella salsuginea (Eutrema halophila) exposed one week to the concentration range 2 – 150 mM and 150 – 350 mM NaCl, respectively, were followed in hydroponics. Time course of the early response (15 min to 24 h) to severe salt stress was also studied. Responses were characterised by phytohormone contents, selected gene transcription, membrane stability, and Na+ and K+ levels.
Thellungiella exhibited higher basal levels of abscisic acid (ABA) and jasmonic acid (JA) in shoot apices in comparison with Arabidopsis. However, the levels of active cytokinins (CKs) were lower (except of cis-zeatin). The halophyte reacted faster and stronger to salt stress (increase of ABA level, and RD26 and COR47 transcription). According to salt stress intensity, four groups may be distinguished on the basis of hormonal and transcriptome changes. Very mild stress (2 – 25 mM NaCl in Arabidopsis) slightly changed transcription of genes involved in CK metabolism. Mild stress in Arabidopsis (50 mM NaCl) induced stress reaction only in apices, while in Thellungiella (150 mM) the hormonal response was detected in whole plant. Severe stress was defined above 75 mM NaCl in the case of Arabidopsis, and above 225 mM in the case of Thellungiella. Lethal stress caused death of Arabidopsis plants (150 mM NaCl).
Generally, JA levels were transiently elevated during the early response. By contrast, salicylic acid content stayed unchanged. Auxin (indole-3-acetic acid) and CKs (primarily trans-zeatin) decreased in roots of both genotypes. The low active CK, cis-zeatin, seems to play an important role during salt stress responses. The results demonstrated that in severe stress the halophyte preferentially protected apices, which died first in Arabidopsis.
This work was supported by MEYS CR, project no. LD 15093.
- Plants protect shoot apical meristem (apex) under salt stress.
- Wide phytohormone range was followed during salt stress response for the first time.
- Hormonome and transcriptome reflect the salt stress strength.
