Comparative Physiological and Transcriptomic Analyses of Two Contrasting Pepper Genotypes under Salt Stress Reveal Complex Salt Tolerance Mechanisms in Seedlings

Abstract

As a glycophyte plant, pepper (Capsicum annuum L.) is widely cultivated worldwide, but its growth is susceptible to salinity damage, especially at the seedling stage. Here, we conducted a study to determine the physiological and transcriptional differences between two genotype seedlings (P300 and 323F3) with contrasting tolerance under salt stress. The P300 seedlings were more salt-tolerant and had higher K+ contents, higher antioxidase activities, higher compatible solutes, and lower Na+ contents in both their roots and their leaves than the 323F3 seedlings. During RNA-seq analysis of the roots, more up-regulated genes and fewer down-regulated genes were identified between salt-treated P300 seedlings and the controls than between salt-treated 323F3 and the controls. Many ROS-scavenging genes and several SOS pathway genes were significantly induced by salt stress and exhibited higher expressions in the salt-treated roots of the P300 seedlings than those of 323F3 seedlings. Moreover, biosynthesis of the unsaturated fatty acids pathway and protein processing in the endoplasmic reticulum pathway were deeply involved in the responses of P300 to salt stress, and most of the differentially expressed genes involved in the two pathways, including the genes that encode mega-6 fatty acid desaturases and heat-shock proteins, were up-regulated. We also found differences in the hormone synthesis and signaling pathway genes in both the P300 and 323F3 varieties under salt stress. Overall, our results provide valuable insights into the physiological and molecular mechanisms that affect the salt tolerance of pepper seedlings, and present some candidate genes for improving salt tolerance in pepper.

Comparative Analysis of Antioxidant System and Salt-Stress Tolerance in Two Hibiscus Cultivars Exposed to NaCl Toxicity

“…Therefore, it is speculated that the old leaves of BS will fall off due to the accumulation of too much Na + under high NaCl conditions. The excess accumulation of Na + in plant cells will induce cytosolic K + efflux and then lead to an imbalance in cellular homeostasis [ 46 , 47 ]. In this study, the K + content in the leaves of the two hibiscus cultivars decreased with the increase in NaCl concentration, which is in contrast to that of intracellular Na + , implying that high NaCl concentration on the outside leads to an increase in Na + content in cells, which in turn causes cytosolic K + efflux in hibiscus leaves.…”

Prosystemin N-terminal protein fragments mitigate salt stress damages in tomato plants

“…These results correlate with the improved performance of salinized plants showing an increased value in their shoot and in their stomatal density. It was demonstrated that a salt tolerant pepper genotype showed a much higher level of transcripts of CAT2, APX2 and other antioxidant genes in respect to susceptible genotype when subjected to salt stress (Zhang et al, 2022) suggesting a correlation between ROS scavenger and plant performance in salt stress conditions. Moreover, increased root biomass is often associated with an enhanced tolerance to salinity and drought stresses and in this context an important role is played by HSP90 (Yadav et al, 2021), also upregulated following plant treatments with speci c EFs.…”