Physiological and molecular insights into the effect of a seaweed biostimulant on enhancing fruit yield and drought tolerance in tomato

Tomato is one of the most widely grown vegetable crops in Europe. This study describes an approach for treating
tomato plants with an extract of Ascophyllum nodosum (ANF) prior to a stress event, which prepares the plants at
the molecular level to respond more effectively to stress conditions, through a process known as molecular
priming. Solanum lycopersicum L. cv. Micro-Tom, a dwarf tomato variety, was pre-treated with ANF via foliar
spray during the flowering phase and subsequently subjected to drought conditions. ANF-treated plants exhibited
enhanced growth, fruit yield, and stress tolerance under both moderate and severe drought conditions compared
to untreated plants. Transcriptomic studies in leaves revealed that the priming treatment preserved the photosynthetic
machinery, inducing stress-protective genes involved in ascorbate, peroxidase, GABA, glutathione, and
flavanol biosynthesis. Simultaneously, the treatment repressed key senescence-related genes associated with
ethylene biosynthesis, as well as several WRKY and NAC transcription factors. Metabolome analysis demonstrated
that ANF induces drought tolerance by promoting the accumulation of stress-protective primary and
secondary metabolites, such as GABA, proline, maltose, ascorbic acid, quercetin, and biotin, which can act as
osmoprotectants and free radical scavengers during drought. Combined transcriptome and metabolome analyses
suggest that ANF treatment represses the senescence process, maintains photosynthetic activity, and induces the
accumulation of protective metabolites and amino acids, promoting plant survival and growth under drought.
Overall, this research provides new insights into the molecular mechanisms underlying biostimulant-based
molecular priming and offers a knowledge-based approach for the accurate application of this ANF molecular
priming agent to increase crop productivity and mitigate yield loss during drought, contributing to food security
in the era of climate change.