Melatonin-governed growth and metabolome divergence: Circadian and stress responses in key plant species
Soundaryaa Bargunam, Riyan Roy, Devika Shetty, Amisha S. H, V Shukla, Vidhu Sankar Babu
Abstract
Melatonin, a versatile biomolecule, profoundly influences plant growth and resilience through its intricate regulation of metabolic pathways, circadian rhythms, and cellular processes. The current study elucidates melatonin's concentration-dependent biphasic effects on growth dynamics in Arabidopsis thaliana and Brassica nigra . While 50 μM melatonin optimized biomass accumulation and root elongation, higher concentrations (100 μM) elicited stress responses, underscoring its dual role as a growth promoter and stress modulator. Melatonin extended photosynthetic efficiency by modulating chlorophyll and carotenoid synthesis diurnally, offering protection against photodamage. Divergent responses between the two species, driven by species-specific metabolic reprogramming, were evident in pigment biosynthesis and antioxidant pathways. B. nigra displayed robust activation of flavonoid and phenylpropanoid pathways, cytokinin signaling, and enhanced oxidative defenses, contrasting with A. thaliana , where melatonin suppressed pigment precursors and antioxidant activation. Metabolomic analysis revealed melatonin's orchestration of hormonal crosstalk, involving auxins, gibberellins, and jasmonates, to fine-tune growth and stress adaptation. Stomatal dynamics and cell wall fortification in B. nigra highlighted melatonin's role in optimizing water-use efficiency and structural resilience under abiotic stress. Cytogenetic studies confirmed melatonin's role in safeguarding genomic integrity, regulating chromatin remodeling, and promoting DNA repair mechanisms, with B. nigra demonstrating adaptive genomic strategies under stress. Moreover, melatonin influenced critical metabolic pathways, including polyamine biosynthesis, sulfur metabolism, and nucleotide regulation, emphasizing its multifaceted impact on cellular homeostasis. These findings position melatonin as a cornerstone molecule in plant biotechnology, with potential applications in enhancing crop resilience and productivity under fluctuating environmental conditions. Elucidating the multifaceted modulatory impacts of exogenous melatonin applications on plant physiological and biochemical pathways: Melatonin-treated plants exhibit diminished anthocyanin synthesis and augmented pigment fidelity. Stomatal mechanics are optimized, alongside equilibrated osmoregulatory capacity. The genomic architecture is refined, characterized by a reduction in nucleotide proliferation which expedites transcriptional and replicative processes. Concurrently, phytodefence pathways are fortified, and mitotic rates are elevated. Collectively, these changes facilitate accelerated phenotypic development and enhance resilience to environmental stressors. • Melatonin orchestrates resilience across metabolic and circadian modulation. • It catalyzes auxin-enhanced root and cellular proliferation in A. thaliana . • It strengthens B. nigra's antioxidant capacity and stomatal responses to stress. • It boosts photosynthesis and pigment synthesis, minimizing photodamage. • It safeguards genomic stability through DNA repair and chromatin restructuring.