Metabolic signatures of germination triggered by kinetin in Medicago truncatula

Abstract

In the present work, non-targeted metabolomics was used to investigate the seed response to kinetin, a phytohormone with potential roles in seed germination, still poorly explored. The aim of this study was to elucidate the metabolic signatures of germination triggered by kinetin and explore changes in metabolome to identify novel vigor/stress hallmarks in Medicago truncatula . Exposure to 0.5 mM kinetin accelerated seed germination but impaired seedling growth. Metabolite composition was investigated in seeds imbibed with water or with 0.5 mM kinetin collected at 2 h and 8 h of imbibition, and at the radicle protrusion stage. According to Principal Component Analysis, inositol pentakisphosphate, agmatine, digalactosylglycerol, inositol hexakisphosphate, and oleoylcholine were the metabolites that mostly contributed to the separation between 2 h, 8 h and radicle protrusion stage, irrespective of the treatment applied. Overall, only 27 metabolites showed significant changes in mean relative contents triggered by kinetin, exclusively at the radicle protrusion stage. The observed metabolite depletion might associate with faster germination or regarded as a stress signature. Results from alkaline comet assay, highlighting the occurrence of DNA damage at this stage of germination, are consistent with the hypothesis that prolonged exposure to kinetin induces stress conditions leading to genotoxic injury.

Hydropriming and Biopriming Improve Medicago truncatula Seed Germination and Upregulate DNA Repair and Antioxidant Genes

“…The next step was to examine the expression patterns of genes that play roles in DNA repair and antioxidant defense, previously used as indicators of seed quality during the early stages of germination (namely seed imbibition) [5][6][7][8]. This is a rather important aspect because such molecular indicators allow the prediction of seed quality in a very short time, thus providing assistance to Seed Companies to design customized priming protocols [2,3,9,10].…”

“…In our previous works, we reported that genes playing roles in DNA repair and antioxidant responses can be used as indicators of seed quality and seeding growth [5][6][7][8]. Here we focused on the expression patters of OGG1 (8-Oxoguanine DNA glycosylase) and FPG (Formamidopyrimidine-DNA glycosylase), involved in Base Excision Repair (BER), APX (Ascorbate peroxidase) and SOD (Superoxide dismutase), encoding known ROS scavengers, and MT2 (Metallothionein type 2), proven to act both as ROS scavenger and repair enzyme [41].…”

“…This is characterized by rapid water uptake, which in turn activates a series of dynamic biochemical events such as the use of reserve storage compounds (lipids, carbohydrates, proteins), production of reactive oxygen species (ROS) and subsequent activation of antioxidant enzymes, DNA damage sensing and repair [3]. Indeed, intense DNA repair, essential for de novo DNA synthesis in embryo cells [4], and enhanced antioxidant functions are the prerequisites of a successful germination process and can be used as molecular markers of seed vigour [5][6][7][8][9].…”

“…The efficacy on the treatments was evaluated based on phenotypic (germination parameters and seedling biometric measurements) and molecular (expression profiles of genes involved in DNA repair and antioxidant response) aspects. Investigating the expression profiles of genes that can be used as indicators of seed quality and seeding growth [5][6][7][8] is intended to speed up the selection of high-quality seed lots. For instance, OGG1 (8-Oxoguanine glycosylase) and FPG (Formamidopyrimidine-DNA glycosylase) genes, playing similar roles within the BER (Base Excision Repair) pathway, were previously shown to be upregulated during seed imbibition in M. truncatula [29].…”

A Snapshot of the Trehalose Pathway During Seed Imbibition in Medicago truncatula Reveals Temporal- and Stress-Dependent Shifts in Gene Expression Patterns Associated With Metabolite Changes

“…As different metabolic pathways are being reactivated during seed imbibition, in previous works we monitored the changes in metabolite profiles using a non-targeted metabolomics approach (Pagano et al, 2019;Araújo et al, 2019). From the generated datasets, here we have extrapolated only the changes in the carbohydrate metabolic pathway since trehalose is included in this category (Figure 3).…”