Transcript Analysis of Two Spinach Cultivars Reveals the Complexity of Salt Tolerance Mechanisms

Increasing soil salinization threatens
global crop productivity.
An understanding of the genetic networks involved in salinity tolerance
mechanisms of high-value crops, such as spinach, is lacking. RNA-Seq
analysis of leaves and roots of two spinach genotypes, Monstrans Viroflag
and Palek, subjected to high-salinity irrigation, revealed that a
higher degree of differential gene expression was caused by salinity
rather than by genotype. Genotypic comparisons suggested that the
low salt tolerance index for root and shoot biomass of Palek, compared
to Monstrans Viroflag, was due to the differential expression of genes
involved in water/nutrient uptake rather than tissue salt accumulation.
Montrans Viroflag displayed a better Cl- exclusion than
Palek and was more efficient in restricting Na+ from entering
its roots, thus protecting leaves from ion toxicity. In addition,
differentially expressed genes (DEGs) involved in MAPK signaling,
hormonal signaling, and transport revealed salinity- and genotype-specific
differences and resulted in the identification of candidate genes
that may function to mediate ion influx across cell membranes to maintain
osmotic homeostasis when plants are under salt stress. The quantitative
reverse transcription assay validated the overall expression trends
of the selected RNA-Seq-based DEGs among different spinach samples.
Collectively, the assays used in this study highlighted the complexity
of the salinity tolerance mechanism and isolated several putative
genes with the potential to improve salinity tolerance in spinach.