Melatonin interaction with abscisic acid in the regulation of abiotic stress in Solanaceae family plants

Abstract

Solanaceous vegetable crops are cultivated and consumed worldwide. However, they often confront diverse abiotic stresses that significantly impair their growth, yield, and overall quality. This review delves into melatonin and abscisic acid (ABA) biosynthesis and their roles in abiotic stress responses. It closely examines the intricate interplay between melatonin and ABA in managing stress within plants, revealing both collaborative and antagonistic effects and elucidating the underlying molecular mechanisms. Melatonin and ABA mutually influence each other's synthesis, metabolism and that of other plant hormones, a key focus of this study. The study highlights melatonin's role in aiding stress management through ABA-dependent pathways and key genes in the melatonin-ABA interaction. Specifically, melatonin downregulates ABA synthesis genes and upregulates catabolism genes, leading to reduced ABA levels. It also directly scavenges H₂O₂, enhancing antioxidant enzyme activities, thereby underscoring their collaborative role in mediating stress responses. Moreover, the interplay between melatonin and ABA plays an essential role in multiple physiological processes of plants, including stomatal behaviors, wax accumulation, delay leaf senescence, seed germination, and seedlings growth, among others. Recognizing these relationships in Solanaceae vegetable crops holds great importance for improving agricultural practices and crop quality. In summary, this review offers a comprehensive overview of recent studies on the melatonin and ABA interplay, serving as a valuable resource for researchers and breeders dedicated to fortifying crop resilience and productivity within challenging environments.

Keywords: Solanaceae plants; abiotic stress responses; abscisic acid; crop improvement; hormonal interplay; horticultural practices; melatonin; molecular mechanisms.

Figure 1

Melatonin biosynthesis pathway through tryptophan metabolism in plants. Tryptophan Decarboxylase (Enzyme); N-Acetyl Transferase (Enzyme); N-Acetyl Serotonin O-Methyl Transferase (Enzyme); Tryptophan (Hormone Precursor); Serotonin (Hormone); Melatonin (Hormone); N-Acetyl Serotonin (Hormone Precursor).

Figure 2

ABA biosynthesis and signaling pathway. Zeaxanthin – ABA Precursor; Violaxanthin - Intermediate output in ABA biosynthesis; Neoxanthin - Intermediate output in ABA biosynthesis; Xanthoxin - Intermediate output in ABA biosynthesis; Abscisic Aldehyde – Intermediate output in ABA biosynthesis; Abscisic Acid - Output.

Figure 3

Interplay of melatonin and ABA in the plant systems under various abiotic stress signal perceptions. Upon exposure of plants to different abiotic stresses, their receptors initiate stress signal transduction, triggering subsequent melatonin production and absorption. Elevated melatonin levels enhance antioxidant activity, facilitating the scavenging of reactive oxygen species (ROS). This defensive mechanism shields plants systems against oxidative damage, and retarding leaf senescence. The response varies based on the specific abiotic stressor; stress-related gene modulation occurs, involving genes such as ABA synthesis-related NCED, ABA catabolism-associated CYP7A, and RBOHD genes, among others. Melatonin plays a pivotal role in phytohormone regulation, influencing the secretion of various plant hormones, including ABA (Abscisic Acid), Ethylene, and GA (Gibberellin). This multifaceted hormone orchestrates processes such as stomatal closure in response to drought, enhancement of heat stress tolerance, promoting seed germination and seedling growth by balancing ABA and GA, and promotion of fruit ripening via upregulating of ABA, H₂O_2, and Ethylene signaling pathways.