Linking Dynamic Phenotyping with Metabolite Analysis to Study Natural Variation in Drought Responses of Brachypodium distachyon

Abstract

Drought is an important environmental stress limiting the productivity of major crops worldwide. Understanding drought tolerance and possible mechanisms for improving drought resistance is therefore a prerequisite to develop drought-tolerant crops that produce significant yields with reduced amounts of water. Brachypodium distachyon (Brachypodium) is a key model species for cereals, forage grasses, and energy grasses. In this study, initial screening of a Brachypodium germplasm collection consisting of 138 different ecotypes exposed to progressive drought, highlighted the natural variation in morphology, biomass accumulation, and responses to drought stress. A core set of ten ecotypes, classified as being either tolerant, susceptible or intermediate, in response to drought stress, were exposed to mild or severe (respectively, 15 and 0% soil water content) drought stress and phenomic parameters linked to growth and color changes were assessed. When exposed to severe drought stress, phenotypic data and metabolite profiling combined with multivariate analysis revealed a remarkable consistency in separating the selected ecotypes into their different pre-defined drought tolerance groups. Increases in several metabolites, including for the phytohormones jasmonic acid and salicylic acid, and TCA-cycle intermediates, were positively correlated with biomass yield and with reduced yellow pixel counts; suggestive of delayed senescence, both key target traits for crop improvement to drought stress. While metabolite analysis also separated ecotypes into the distinct tolerance groupings after exposure to mild drought stress, similar analysis of the phenotypic data failed to do so, confirming the value of metabolomics to investigate early responses to drought stress. The results highlight the potential of combining the analyses of phenotypic and metabolic responses to identify key mechanisms and markers associated with drought tolerance in both the Brachypodium model plant as well as agronomically important crops.

Variation in functional responses to water stress and differentiation between natural allopolyploid populations in the Brachypodium distachyon species complex

“…Drought response has been investigated mainly in the diploid B. distachyon, given its emerging role as a plant model for temperate grasses (e.g. Luo et al, 2011;Verlest et al, 2013;Des Marais and Juenger, 2016;Fisher et al, 2016). However, the adaptive significance of natural variation observed in the drought physiology of this species complex is not well understood yet (but see Manzaneda et al, 2015;Des Marais et al, 2017).…”

“…While that previous study was limited to only two species of the complex, here we firstly deepen the study of the significance of trait divergence among the three species by analysing specific differentiation in leaf traits typically related to drought response (e.g. Fisher et al, 2016;Des Marais et al, 2017), such as water content, specific leaf area, electrolyte leakage, proline content and phytohormone content. Secondly, we analyse the differentiation of drought-tolerance-related traits between B. hybridum Iberian populations that are genetically distinct, and whether such phenotypic differentiation between B. hybridum populations is related to aridity.…”

Novel Digital Features Discriminate Between Drought Resistant and Drought Sensitive Rice Under Controlled and Field Conditions

“…Non-destructive imaging was shown to be an effective method for measuring drought response in plant. Plant area, estimated from images, is considered as a proxy for biomass and plant growth, and has been adopted to evaluate and quantify the plant response to drought stress (Honsdorf et al, 2014 ; Petrozza et al, 2014 ; Fisher et al, 2016 ; Malinowska et al, 2017 ). However, as organ occlusion becomes more pronounced (for instance, for many cereals including rice and wheat at the reproductive stages), the accuracy of projected plant area for estimating the biomass and plant growth decreases (Munns et al, 2010 ).…”

“…Optical imaging and computer-assisted feature extraction have the advantages of being non-destructive, potentially high-throughput and objective. They have been widely applied in phenotyping plant growth and development (Spalding and Miller, 2013 ; Duan et al, 2015 ; Montagnoli et al, 2016 ; Rebolledo et al, 2016 ), seeds (Duan et al, 2011 ), root systems (Lobet et al, 2017 ), plant disease symptoms (Mutka and Bart, 2014 ), and plant abiotic stress (Altamimi et al, 2016 ; Fisher et al, 2016 ; Malinowska et al, 2017 ).…”

Review: Omics and Strategic Yield Improvement in Oil Crops

“…Hence, lines with stable yield traits could be used in future rice breeding programs. Phenotyping drought tolerance characteristics and association with metabolomics coupled with multivariate analysis have provided leads into understanding plant early response to drought and plant adaptation [234][235][236]. Identification of key mechanisms such as mobilization of carbohydrates to support aerial growth at the expense of the roots indicated that growth and biomass production are key phenotypic traits to observe for drought tolerance screening.…”