Tiantian Ye

Gibberellins (GAs) play a pivotal role in modulating plant growth and development. Glucose–conjugated gibberellins (Glc–GAs), a prevalent conjugated form of GAs, regulate intracellular GA levels by the coupling and decoupling of glucose groups. However, the diversity of Glc–GAs identified within individual species remains limited, hinting at a multitude of yet undiscovered gibberellin metabolites. This lacuna poses considerable impediments to research efforts dedicated to comprehensively delineating the GA metabolic pathway. In this study, we developed a structure–oriented screening and identification method for Glc–GAs in plant species by employing LC–MS/MS coupled with chemical derivatization. Through the application of chemical derivatization technique, carboxyl groups on Glc–GAs were labeled which effectively enhanced the sensitivity and selectivity of mass spectrometry detection for these compounds. Concurrently, the integration of mass spectrometry fragmentation and chromatographic retention behavior facilitated the efficient screening and identification of potential Glc–GAs. With this strategy, we screened and identified 12 potential Glc–GAs from six plant species. These findings expand the Glc–GA diversity in plants and contribute to understanding GA metabolic pathways.

Phaseic acid (PA), a main catabolite of abscisic acid (ABA), is structurally related to ABA and possesses ABA-like hormonal activity. However, the comprehensive metabolism pathway and roles of PA are not well understood. Here, using homologous alignment and expression pattern analysis, we identified in Arabidopsis the previously named CRL1 (Cinnamoyl coA: NADP oxidoreductase-like 1) as a PA reductase that catalyses PA to dihydrophaseic acid. The function of CRL1 and the potential role of PA were studied in transgenic CRL1 plants. Overexpression of CRL1 resulted in decreased ABA sensitivity in seed germination and attenuated drought tolerance. In contrast, increased ABA sensitivity and elevated drought tolerance was observed in down-regulated and loss-of-function crl1 mutants. Tyr162 in the conserved motif is the key residue in CRL1 to catalyse PA. Accelerated seed germination and earlier flowering phenotype were also observed in overexpressing lines, while retarded seed germination and delayed flowering occurred in crl1 mutants which accumulated more PA, but less dihydrophaseic acid than the wild type. This study demonstrates that PA plays diverse functions in drought tolerance, seed germination and flowering in an ABA-like manner, which may increase the adaptive plasticity of plants.