Steady-State Levels of Cytokinins and Their Derivatives May Serve as a Unique Classifier of Arabidopsis Ecotypes

Abstract

We determined steady-state (basal) endogenous levels of three plant hormones (abscisic acid, cytokinins and indole-3-acetic acid) in a collection of thirty different ecotypes of Arabidopsis that represent a broad genetic variability within this species. Hormone contents were analysed separately in plant shoots and roots after 21 days of cultivation on agar plates in a climate-controlled chamber. Using advanced statistical and machine learning methods, we tested if basal hormonal levels can be considered a unique ecotype-specific classifier. We also explored possible relationships between hormone levels and the prevalent environmental conditions in the site of origin for each ecotype. We found significant variations in basal hormonal levels and their ratios in both root and shoot among the ecotypes. We showed the prominent position of cytokinins (CK) among the other hormones. We found the content of CK and CK metabolites to be a reliable ecotype-specific identifier. Correlation with the mean temperature at the site of origin and the large variation in basal hormonal levels suggest that the high variability may potentially be in response to environmental factors. This study provides a starting point for ecotype-specific genetic maps of the CK metabolic and signalling network to explore its contribution to the adaptation of plants to local environmental conditions.

Signal Integration in Plant Abiotic Stress Responses via Multistep Phosphorelay Signaling

“…In the light of several recent findings, implicating cytokinin-regulated MSP signaling (through type-B ARRs) in the control over context-dependent chromatin accessibility ( Potter et al, 2018 ), the well-documented (cytokinin-modulated) role of ethylene in histone acetylation and ABA-dependent regulation of chromatin-remodeling complexes (see above), we can venture to say that epigenetic regulations form part of the repertoire of transcription regulatory tools available to MSP (and interconnected signaling pathways), possibly mediating environmental “memory” used by the plants in their adaptation to short- and medium-term environmental fluctuations. In line with this, Samsonová et al (2020) showed that cytokinins occupy a prominent position among other hormones as unique ecotype identifiers. A positive correlation between mean ABA content and ABA/cytokinin ratio in the shoots with mean temperature at the site of origin is in line with existing data on the involvement of cytokinin signaling in the cold response (see above).…”

“…This then means that control over cytokinin metabolism is one of the mechanisms involved in long-term adaptation. Also, the large variability in the ABA/cytokinin ratios observed among the ecotypes in both shoots and roots suggests hormonal plasticity, which might contribute to and/or determine stress responses in particular geographical regions ( Samsonová et al, 2020 ).…”

Cytokinin glucosyl transferases, key regulators of cytokinin homeostasis, have potential value for wheat improvement

“…Unfortunately, many researchers choose to ignore the cytokinin glucosides altogether. While it could be the case that relatively few research groups have the knowledge and/or capability to analyse multiple cytokinin forms, these forms should not be ignored (Samsonová et al ., 2020). This is because strong homeostatic mechanisms operate (e.g.…”