Climate change reshapes the physiology and development of organisms through phenotypic plasticity, epigenetic modifications, and genetic adaptation. Under evolutionary pressures of the sessile lifestyle, plants possess efficient systems of phenotypic plasticity and acclimation to environmental conditions. Molecular analysis, especially through omics approaches, of these primary lines of environmental adjustment in the context of climate change has revealed the underlying biochemical and physiological mechanisms, thus characterizing the links between phenotypic plasticity and climate change responses. The efficiency of adaptive plasticity under climate change indeed depends on the realization of such biochemical and physiological mechanisms, but the importance of sensing and signaling mechanisms that can integrate perception of environmental cues and transduction into physiological responses is often overlooked. Recent progress opens the possibility of considering plant phenotypic plasticity and responses to climate change through the perspective of environmental sensing and signaling. This review aims to analyze present knowledge on plant sensing and signaling mechanisms and discuss how their structural and functional characteristics lead to resilience or hypersensitivity under conditions of climate change. Plant cells are endowed with arrays of environmental and stress sensors and with internal signals that act as molecular integrators of the multiple constraints of climate change, thus giving rise to potential mechanisms of climate change sensing. Moreover, mechanisms of stress-related information propagation lead to stress memory and acquired stress tolerance that could withstand different scenarios of modifications of stress frequency and intensity. However, optimal functioning of existing sensors, optimal integration of additive constraints and signals, or memory processes can be hampered by conflicting interferences between novel combinations and novel changes in intensity and duration of climate change-related factors. Analysis of these contrasted situations emphasizes the need for future research on the diversity and robustness of plant signaling mechanisms under climate change conditions.

SUMMARY Jasmonate signaling for adaptative or developmental responses generally relies on an increased synthesis of the bioactive hormone jasmonoyl‐isoleucine (JA‐Ile), triggered by environmental or internal cues. JA‐Ile is embedded in a complex metabolic network whose upstream and downstream components strongly contribute to hormone homeostasis and activity. We previously showed that JAO2, an isoform of four Arabidopsis JASMONIC ACID OXIDASES, diverts the precursor jasmonic acid (JA) to its hydroxylated form HO‐JA to attenuate JA‐Ile formation and signaling. Consequently, JAO2‐deficient lines have elevated defenses and display improved tolerance to biotic stress. Here we further explored the organization and regulatory functions of the JAO pathway. Suppression of JAO2 enhances the basal expression of nearly 400 JA‐regulated genes in unstimulated leaves, many of which being related to biotic and abiotic stress responses. Consistently, non‐targeted metabolomic analysis revealed the constitutive accumulation of several classes of defensive compounds in jao2‐1 mutant, including indole glucosinolates and breakdown products. The most differential compounds were agmatine phenolamides, but their genetic suppression did not alleviate the strong resistance of jao2‐1 to Botrytis infection. Furthermore, jao2 alleles and a triple jao mutant exhibit elevated survival capacity upon severe drought stress. This latter phenotype occurs without recruiting stronger abscisic acid responses, but relies on enhanced JA‐Ile signaling directing a distinct survival pathway with MYB47 transcription factor as a candidate mediator. Our findings reveal the selected spectrum of JA responses controlled by the JAO2 regulatory node and highlight the potential of modulating basal JA turnover to pre‐activate mild transcriptional programs for multiple stress resilience.

Gibberellic acid (GA) is a major plant hormone involved in several biological processes from the flowering to the symbiosis with microorganisms. Thus, the GA regulation is crucial for plant biology. This regulation occurs via the DELLA proteins that belong to the GRAS transcription factor family. DELLA proteins are characterised by a DELLA N-terminal and a GRAS C-terminal domains. It is well known that DELLA activity appears after the bryophytes divergence and then evolved in the vascular plant lineages. Here we present the phylogeny of DELLA across 75 species belonging to various lineages from algae, liverworts and angiosperms. Our study confirmed two main duplication events, the first occurring before the angiosperms divergence and the other specific to the eudicots lineage. Comparative analysis of DELLA subclades in angiosperms revealed the loss in Poaceae and strong alteration in other species of the DELLA functional domain in the DELLA2 clade. In addition, molecular evolution analysis suggests that each of the clades (named DELLA1.1, DELLA1.2 and DELLA2) evolved differently but copies of each subclade are under strong purifying selection. This also suggests that, although the DELLA functional domain is altered in DELLA2, DELLA2 orthologs are still functional and operate in a different way compared to DELLA1 copies. In angiosperms, additional duplication events occurred and led to duplicate copies in species, genus or family such as in the Fabaceae subfamily Papilionoideae. This duplication led to the formation of additional paralogs in the DELLA1.2 subclade (DELLA1.2.1 and DELLA1.2.2). Interestingly, both copies appeared to be under relaxing selection revealing different evolutionary fate of the DELLA duplicated copies.