Abstract
Abiotic stress, such as drought and salinity, severely affect the growth and yield of many plants. Oenanthe javanica (commonly known as water dropwort) is an important vegetable that is grown in the saline-alkali soils of East Asia, where salinity is the limiting environmental factor. To study the defense mechanism of salt stress responses in water dropwort, we studied two water dropwort cultivars, V11E0022 and V11E0135, based on phenotypic and physiological indexes. We found that V11E0022 were tolerant to salt stress, as a result of good antioxidant defense system in the form of osmolyte (proline), antioxidants (polyphenols and flavonoids), and antioxidant enzymes (APX and CAT), which provided novel insights for salt-tolerant mechanisms. Then, a comparative transcriptomic analysis was conducted, and Gene Ontology (GO) analysis revealed that differentially expressed genes (DEGs) involved in the carbohydrate metabolic process could reduce oxidative stress and enhance energy production that can help in adaptation against salt stress. Similarly, lipid metabolic processes can also enhance tolerance against salt stress by reducing the transpiration rate, H2O2, and oxidative stress. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that DEGs involved in hormone signals transduction pathway promoted the activities of antioxidant enzymes and reduced oxidative stress; likewise, arginine and proline metabolism, and flavonoid pathways also stimulated the biosynthesis of proline and flavonoids, respectively, in response to salt stress. Moreover, transcription factors (TFs) were also identified, which play an important role in salt stress tolerance of water dropwort. The finding of this study will be helpful for crop improvement under salt stress.
Highlights
Salinity, an abiotic stressor, has a significant impact on plant productivity [1]
To detect whether plant growth properties were affected by salinity in both treated cultivars, we compared vegetative parameters of two water dropwort cultivars and found that plant height, stem length, root length, number of branches, number of leaves, and shoot and root fresh biomass in the treatments were significantly lower than the control (Figure 1)
It was suggested that proline, flavonoids, ascorbate peroxidase (APX), and CAT could play an efficient role in the tolerance of water dropwort against salt stress in comparison to other studied parameters
Summary
An abiotic stressor, has a significant impact on plant productivity [1]. A high concentration of salt leads to osmotic stress and ionic imbalance in plants, which in turn affect plant physiology, decreased biomass and biochemical processes, and lead to plant injury or death [2,3]. Previous physiological studies mentioned that salt stress induces oxidative stress through the formation of reactive oxygen species (ROS) in the form of superoxide (O2 − ), hydrogen peroxide (H2 O2 ), and hydroxyl radicals ( OH), which affects the cellular structures and metabolism of the plants as a result [7,8]. Proline is produced from either ornithine or glutamate in osmotically stressed cells. It possesses ROS scavenging activity and enhances the activity of antioxidant enzymes [11,12]. Antioxidant molecules including polyphenols and flavonoids help to minimize the negative effects of salt stress by removing free radicals, which enhances the tolerance against salt stress [13]
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