Distinct Metabolome Changes during Seed Germination of Lettuce (Lactuca sativa L.) in Response to Thermal Stress as Revealed by Untargeted Metabolomics Analysis

Abstract

Temperature strongly influences lettuce (Lactuca sativa L.) seed germination. Different lettuce genotypes respond differently to higher temperatures or thermal stress. In this study, we evaluated the germination performance of 304 lettuce accessions incubated at three temperature settings, 21 °C, 28 °C and 35 °C, respectively, for 40 h. At 21 °C, seeds of all 304 accessions germinated with very well an average germination percentage of 87.72%; at 28 °C, the average germination percentage dropped to 42.84% and at 35 °C, the germination decreased to 1.01%. Then, we investigated changes in metabolic profiles of lettuce seed response to thermal stress using an untargeted metabolomics approach. Results suggested that seeds of thermal-sensitive and thermal-tolerant cultivars employed different metabolic strategies in response to thermal stress during germination. Thermal-sensitive buds accumulated more significant amounts of organic acids, amino acids, sugars, sterols, phenolic compounds and terpenoids compared to thermal-tolerant buds at 21 °C. Thermal-tolerant lettuce cultivar accumulated higher concentrations of amino acids, organic acids, sugars, sesquiterpene lactones, sterols, and fatty acids derivatives during the germination at 35 °C compared to germinated at 21 °C. This investigation paves the way to link the metabolomics to other external and internal factors affecting lettuce seed germination under thermal stress.

Intraspecific Variability Largely Affects the Leaf Metabolomics Response to Isosmotic Macrocation Variations in Two Divergent Lettuce (Lactuca sativa L.) Varieties

“…Our current understanding of how the controlled manipulation of multiple mineral elements interacts on a pre-existing phytochemical diversity in plants is very limited, also because, for instance, different studies have been carried out in relation to an exposure to abiotic stress conditions [51][52][53][54]. The analysis of the effects on the NS in relation to the different colored genotypes provided interesting insights.…”

Metabolomics: a systems biology approach for enhancing heat stress tolerance in plants

“…N106 accumulated higher levels of amino and organic acids, sugars, sesquiterpene lactones, sterols, and fatty acids derivatives throughout the germination at 35 °C. These findings cover how to connect the metabolomics to additional external and interior influences, disturbing lettuce seed germination under HS (Wei et al 2020). Numerous untargeted metabolomics researches reported that salicylic acid, ascorbic acid, phenolic secondary metabolites, and almost all antioxidant defense enzymes could lessen HS indicators in several plant species (Zhang et al 2017;Mobin et al 2017;Muhlemann et al 2018;Salvi et al 2018).…”

“…Recently, Wei et al (2020) investigated the metabolic response of lettuce (Lactuca sativa L.) seed under HS via an untargeted metabolome profiling. The results showed that seeds of heat-tolerant (N106) and heat-sensitive (N62) cultivars employed diverse metabolic stratagems in response to HS throughout germination.…”

“…Conclusively, several DPMs have been identified that are unique to only heat-tolerant cultivar in several plant species. For example, in rice, the polyols, Myo-inositol, putrescine and glycerol (Lawas et al 2019); cysteine, serine, and threonine, cytokinin, uridine diphosphate glucose, coumarylalcohol, and α-l-rhamnose (Wada et al 2020); in lettuce, amino and organic acids, sugars, sesquiterpene lactones, sterols, and fatty acids derivatives (Wei et al 2020), in pepper, citrulline, serine, cysteine, glutamine, homocitrulline, alanine, and ornithine (Wang et al 2019) were significantly up-regulated and/or accumulated in heat-tolerant cultivars. Additionally, some examples have also been documented in Table 2.…”

A comparative UHPLC-Q/TOF–MS-based eco-metabolomics approach reveals temperature adaptation of four Nepenthes species

“…Metabolomics can contribute significantly to our understanding of stress responses in plants by identifying the involved metabolites in response to endogenous and exogenous stressor 21 – 24 . Applying a nontargeted metabolome approach, combined with high-resolution Mass Spectrometry (MS) and high-resolution chromatography, we can discover true dynamics of biological systems in response to specific perturbations 25 .…”