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

Abstract

Since the 1950s, research on the animal neurohormone, melatonin, has focused on its multiregulatory effect on patients suffering from insomnia, cancer, and Alzheimer's disease. In plants, melatonin plays major role in plant growth and development, and is inducible in response to diverse biotic and abiotic stresses. However, studies on the direct role of melatonin in disease suppression and as a signaling molecule in host-pathogen defense mechanism are lacking. This study provides insight on the predicted biosynthetic pathway of melatonin in watermelon (Citrullus lanatus), and how application of melatonin, an environmental-friendly immune inducer, can boost plant immunity and suppress pathogen growth where fungicide resistance and lack of genetic resistance are major problems. We evaluated the effect of spray-applied melatonin and also transformed watermelon plants with the melatonin biosynthetic gene SNAT (serotonin N-acetyltransferase) to determine the role of melatonin in plant defense. Increased melatonin levels in plants were found to boost resistance against the foliar pathogen Podosphaera xanthii (powdery mildew), and the soil-borne oomycete Phytophthora capsici in watermelon and other cucurbits. Further, transcriptomic data on melatonin-sprayed (1 mmol/L) watermelon leaves suggest that melatonin alters the expression of genes involved in both PAMP-mediated (pathogen-associated molecular pattern) and ETI-mediated (effector-triggered immunity) defenses. Twenty-seven upregulated genes were associated with constitutive defense as well as initial priming of the melatonin-induced plant resistance response. Our results indicate that developing strategies to increase melatonin levels in specialty crops such as watermelon can lead to resistance against diverse filamentous pathogens.

PTEN inhibition attenuates endothelial cell apoptosis in coronary heart disease via modulating the AMPK–CREB–Mfn2‐mitophagy signaling pathway

“…Our current data update the role of PTEN in mitochondrial apoptosis and introduce the role of PTEN in mitophagy regulation for the first time (Mandal, Suren, Ward, Boroujerdi, & Kousik, 2018;Poreba et al, 2019). This finding provides insight into the mechanism by which PTEN deletion preserves mitochondrial function and structure.…”

“…PTEN modulates (Mukherjee et al, ; Owino et al, ) ROS production and regulates mitochondrial ATP production (Nicklas et al, ), affecting cell proliferation and the vulnerability of kidney tubules and myocytes to stress (Y. Wang, Chen, et al, ). Our current data update the role of PTEN in mitochondrial apoptosis and introduce the role of PTEN in mitophagy regulation for the first time (Mandal, Suren, Ward, Boroujerdi, & Kousik, ; Poreba et al, ). This finding provides insight into the mechanism by which PTEN deletion preserves mitochondrial function and structure.…”

Melatonin enhances cotton immunity to Verticillium wilt via manipulating lignin and gossypol biosynthesis

“…tomato ( Pst ) DC3000 (Shi et al ., ,c). Melatonin alters the expression of genes involved in both PAMP‐mediated and ETI‐mediated defense in watermelon leaves during Phytophthora capsici infection (Mandal et al ., ). Therefore, we propose that melatonin mediates broad‐spectrum pathogen resistance in plants via diverse mechanisms, possibly depending on the disease mechanism of the pathogen.…”

“…Plant melatonin also alleviates abiotic stresses from cold, heat, drought, salt, to heavy metals (Shi et al ., ,d; Wei et al ., ; Li et al ., ,c; Ding et al ., ). Studies have implicated melatonin in plant immunity (Yin et al ., ; Lee et al ., ; Shi et al ., ,d; Mandal et al ., ), but the underlying mechanisms remain unclear.…”

Melatonin and Its Protective Role against Biotic Stress Impacts on Plants

“…Also, Qian, et al [42] reported on the participation of sugar and glycerol in melatonin-associated protection against (Pst) DC3000 through SA-and NO-dependent pathways in Arabidopsis [42]. Recently, exogenous melatonin treatment was found to activate ETI-and PTI-associated genes in watermelon and Arabidopsis according to transcriptomic data [40,41]. All of the bactericidal activities of melatonin, the related mechanisms involved, and the resulting constructive effects in plants are summarized in Table 2 and Figure 1.…”