Treatment Analogous to Seasonal Change Demonstrates the Integration of Cold Responses in Brachypodium distachyon

Anthropogenic climate change precipitates the need to understand plant adaptation. Crucial in temperate climates, adaptation to winter is characterized by cold acclimation and vernalization, which respectively lead to freezing tolerance and flowering competence. However, the progression of these responses during fall and their interaction with plant development are not completely understood. By identifying key seasonal cues found in the native range of the cereal model Brachypodium distachyon, we designed a diurnal-freezing treatment (DF) that emulates summer-to-winter change. DF induced unique cold acclimation and vernalization responses characterized by low VERNALIZATION1 (VRN1) expression. Flowering under DF is characterized by an up-regulation of FLOWERING LOCUS T (FT) postvernalization independent of VRN1 expression. DF, while conferring flowering competence, favors a high tolerance to freezing and the development of a winter-hardy plant structure. The findings of this study highlight the contribution of phenotypic plasticity to freezing tolerance and demonstrate the integration of key morphological, physiological, and molecular responses in cold adaptation. The results suggest a fundamental role for VRN1 in regulating cold acclimation, vernalization, and morphological development in B. distachyon This study also establishes the usefulness of reproducing natural cues in laboratory settings.