The role of cytokinin receptors in Arabidopsis thaliana seed development and how they affect the metabolomic profile.

Main conclusion: Based on expression, functional, and metabolomic analyses in the seeds of the single-receptor mutants, each receptor has a specific function during seed development. Their redundant roles during this process are difficult to assess; moreover, the impact they have on plant development must also be taken into account. In this study, we investigated the role of cytokinin receptors in Arabidopsis thaliana seed development and their impact on the metabolomic profile. Our findings reveal distinct expression patterns among them in the seed: AHK2 expression is not detected in seed tissues, AHK3 is expressed in embryo, endosperm, and peripheral endosperm, while AHK4/CRE1 expression is restricted to a few embryo cells. These patterns are consistent with the observed phenotypes where ahk3 exhibits more severe seed phenotypes such as delayed embryo development and increased seed and endosperm size. Metabolomic analyses showed that the receptors impact the abundance of metabolites, with a remarkably high concentration of tannins in ahk2 with respect to wild type seeds, while ahk3 mutant seeds have a very low amount of tannins but elevated levels of other compounds such as sinapoylated glucosinolates (GSLs), important for plant defense. The metabolic profile performed further supports a link between cytokinin and the regulation of secondary metabolites such as flavonoids and glucosinolates. Our results suggest that each cytokinin receptor independently contributes to this regulation, reflected in the distinct metabolic profiles of each mutant.