Diversity in nonlinear responses to soil moisture shapes evolutionary constraints in Brachypodium

Abstract

Water availability is perhaps the greatest environmental determinant of plant yield and fitness. However, our understanding of plant-water relations is limited because—like many studies of organism-environment interaction—it is primarily informed by experiments considering performance at two discrete levels—wet and dry—rather than as a continuously varying environmental gradient. Here we used experimental and statistical methods based on function-valued traits to explore genetic variation in responses to a continuous soil moisture gradient in physiological and morphological traits among ten genotypes across two species of the model grass genus Brachypodium. We find that most traits exhibit significant genetic variation and non-linear responses to soil moisture variability. We also observe differences in the shape of these non-linear responses between traits and genotypes. Emergent phenomena arise from this variation including changes in trait correlations and evolutionary constraints as a function of soil moisture. Our results point to the importance of considering diversity in non-linear organism-environment relationships to understand plastic and evolutionary responses to changing climates.

Revisiting regulatory decoherence and phenotypic integration: accounting for temporal bias in co-expression analyses

“…The degree of stress imposed on the system may dictate whether coherence (or integration) as opposed to decoherence is observed. A possible reconciliation between our results and the decoherence reported by Lea et al, may be that the monocytes studied by Lea et al experienced a relatively more stressful environment than the rice plants studied by Wilkins et al Indeed, we recently showed that trait co-variances vary considerably along a single environmental index (Monroe et al 2021), suggesting that genome-scale regulatory interactions likely transition from coherent to decoherent along such axes. Such gradients of response should be carefully considered during the design of experiments (Poorter et al 2016).…”

Brachypodium: 20 years as a grass biology model system; the way forward?

“…Although the literature describing drought responses in plants is extensive, Brachypodium-based research has made a contribution. At its most basic, an examination of Brachypodium inbred lines grown under range of soil % moisture contents indicated a nonlinear relationship, so simple pairwise comparisons between droughted and fully watered plants could be insufficient [75]. The variation in responses to drought in Brachypodium accessions has been assessed [34,76,77] and, in one case, the degree of drought tolerance related to rainfall in the original sampling sites [78].…”

Growth-limiting drought stress induces time-of-day-dependent transcriptome and physiological responses in hybrid poplar

“…This observation may be related to exponential decreases in soil water potential at low SWCg ( Dowd et al 2019 ), whereby a small change in water volume leads to a large change in water availability. Moreover, physiological and growth traits, including specific leaf area and leaf carbon content, are affected non-linearly by soil water availability ( Monroe et al 2021 ) highlighting the importance of studying these responses under a limited number of discrete soil moisture conditions. To fully characterize plant responses to drought stress, it will be necessary to incorporate intermediate water-limiting conditions to understand how the degree of water stress impacts plant status, rather than an ‘all-or-nothing’ approach.…”

“…Experiments that have directly compared drought-stress responses in controlled and field environments have reported significant differences in physiological responses and gene expression profiles depending on the type of environments where plants were grown ( Lovell et al 2016 ; Wilkins et al 2016 ). Some of these differences can be attributed to the degree or duration of the drought ( Monroe et al 2021 ), or to the underlying complexity of the environment ( Mittler 2006 ; Plessis et al 2015 ). In nature, the onset of drought is often gradual, and plants adjust their physiology and development to minimize damage and optimize growth ( Sohn et al 2013 ).…”