Physiological and Molecular Aspects of Two Thymus Species Differently Sensitive to Drought Stress

Abstract

Drought is one of the most important threats to plants and agriculture. Here, the effects of four drought levels (90%, 55%, 40%, and 25% field capacity) on the relative water content (RWC), chlorophyll and carotenoids levels, and mRNA gene expression of metabolic enzymes in Thymus vulgaris (as sensitive to drought) and Thymus kotschyanus (as a drought-tolerant species) were evaluated. The physiological results showed that the treatment predominantly affected the RWC, chlorophyll, and carotenoids content. The gene expression analysis demonstrated that moderate and severe drought stress had greater effects on the expression of histone deacetylase-6 (HDA-6) and acetyl-CoA synthetase in both Thymus species. Pyruvate decarboxylase-1 (PDC-1) was upregulated in Thymus vulgaris at high drought levels. Finally, succinyl CoA ligase was not affected by drought stress in either species. Data confirmed water stress is able to alter the gene expression of specific enzymes. Furthermore, our results suggest that PDC-1 expression is independent from HDA-6 and the increased expression of ACS can be due to the activation of new pathways involved in carbohydrate production.

Plants’ Physio-Biochemical and Phyto-Hormonal Responses to Alleviate the Adverse Effects of Drought Stress: A Comprehensive Review

“…In wheat (Triticum aestivum), the state of reduced leaf turgor pressure disrupts plant metabolic functions. Under drought conditions, crop development is impeded by a lower soil water potential, and the resulting lowered plant osmotic potential leads to low nutrient absorption [72].…”

“…However, a protracted period of high-intensity limited water conditions might slow plant development, alter the morphological structure and biomass distribution pattern in tomato crops (Solanum lycopersicum L.), or cause mortality [15,85]. Drought stress significantly influences the photosynthetic system and its pigments, such as chlorophyll a, b, and carotenoids [72,86,87]. Drought stress also impacts complex systems such as photosystems I and II.…”

Salicylic Acid Stimulates Defense Systems in Allium hirtifolium Grown under Water Deficit Stress

“…Thus, under SA treatment, glutamic-γ -semi-aldehyde (GSA) converted to pyrroline-5- carboxylate (P5C) in cytosol and chloroplasts and so increased the proline transport [ 28 ]. Mohammadi et al found that SA application caused a significant increase in osmolytes (total carbohydrates and proline) in Thymus kotschyanus and Thymus vulgaris under drought stress conditions [ 10 , 29 , 30 ]. These results agree with our present results, especially soluble sugars (data are not shown).…”

“…Drought is the most common and important environmental stress limiting the yield of many crops and medicinals, especially in arid and semi-arid regions [ 8 , 9 ], which reduces plants yield by more than 50% on average. Drought stress causes a broad range of physiological changes and impairments of metabolic processes, which result in the accumulation of reactive oxygen species (ROS) [ 10 , 11 ].…”

The Therapeutic Potential of Ethnomedicinally Important Anatolian Thyme Species: A Phytochemical and Biological Assessment

“…Owing to their unique leave shapes with dense hairs on them, thymes are known to be quite resistant, and they can survive cold temperatures and aridness ( Morales, 2002 ). Even when they have to face challenging environmental conditions such as drought stress, they were shown to have the ability to develop adaptation to these conditions by activating their stress response and evolving their phytochemistry accordingly ( Mahdavi et al, 2020 ; Ashrafi et al, 2022 ). Over and above, the members of the genus Thymus have significant variations in their morphological characteristics that lead them to be evaluated under a great number of species mostly distributed in the Mediterranean region.…”