Comparative metabolomic analysis highlights the involvement of sugars and glycerol in melatonin-mediated innate immunity against bacterial pathogen in Arabidopsis

Abstract

Melatonin is an important secondary messenger in plant innate immunity against the bacterial pathogen Pseudomonas syringe pv. tomato (Pst) DC3000 in the salicylic acid (SA)- and nitric oxide (NO)-dependent pathway. However, the metabolic homeostasis in melatonin-mediated innate immunity is unknown. In this study, comparative metabolomic analysis found that the endogenous levels of both soluble sugars (fructose, glucose, melibose, sucrose, maltose, galatose, tagatofuranose and turanose) and glycerol were commonly increased after both melatonin treatment and Pst DC3000 infection in Arabidopsis. Further studies showed that exogenous pre-treatment with fructose, glucose, sucrose, or glycerol increased innate immunity against Pst DC3000 infection in wild type (Col-0) Arabidopsis plants, but largely alleviated their effects on the innate immunity in SA-deficient NahG plants and NO-deficient mutants. This indicated that SA and NO are also essential for sugars and glycerol-mediated disease resistance. Moreover, exogenous fructose, glucose, sucrose and glycerol pre-treatments remarkably increased endogenous NO level, but had no significant effect on the endogenous melatonin level. Taken together, this study highlights the involvement of sugars and glycerol in melatonin-mediated innate immunity against bacterial pathogen in SA and NO-dependent pathway in Arabidopsis.

Melatonin mediates the stabilization of DELLA proteins to repress the floral transition in Arabidopsis

“…Total RNA and first‐strand cDNA were extracted and synthesized as previously described. Then quantitative real‐time PCR was performed and analyzed as previously described . The primers for real‐time PCR were shown in Table S1 (Supporting information).…”

“…With the first identification of melatonin ( N ‐acetyl‐5‐methoxytryptamine) in plants in 1995 , melatonin has been widely found to be involved in seed germination, root morphology, rhythm, senescence, crop yield, fruit ripening, stress responses including salt, drought, cold, heat, heavy metal, oxidative stress, and plant – pathogen interaction . As a crucial messenger in plants, the possible involvement of melatonin in flowering and underlying molecular mechanism are unknown in Arabidopsis .…”

Differential roles of melatonin in plant‐host resistance and pathogen suppression in cucurbits

“…In plants, melatonin reprograms cellular functions by activating expression of defense‐related genes against diverse biotic and abiotic stresses. For example, recent studies on melatonin’s role in triggering plant immunity against the bacterial pathogen Pseudomonas syringae pv tomato ( pst ) DC3000 in Arabidopsis plants provided evidence of its role in salicylic acid‐mediated plant defense signaling . Characterization of Arabidopsis serotonin N‐acetyltransferase knockout (At SNAT KO ) mutant plants exhibits decreased melatonin and salicylic acid levels resulting in susceptibility to an avirulent bacterial pathogen .…”

Overexpression of rice serotonin N‐acetyltransferase 1 in transgenic rice plants confers resistance to cadmium and senescence and increases grain yield

“…Since the first discovery of melatonin in plants in 1995, many pharmacological studies have been performed to investigate its functional and physiological significance . Large numbers of experiments involving exogenous application of melatonin to a series of plant species indicated that melatonin acts as a biostimulator in plants by enhancing a myriad of defense responses against abiotic stresses, including oxidative stress, high temperature, cold, senescence, drought, and salt, as well as biotic stress such as pathogen attacks . In addition to the defense responses, melatonin has also been implicated in promoting plant growth processes, such as seedling growth, flowering, nutrient absorption, and fruit ripening, suggesting a potential role of melatonin as a plant growth factor .…”