Abstract
Leaf senescence represents the last stage of leaf development and is highly regulated by plant hormones and environmental factors. Leaf senescence limits growth and yields in crops, leading to a significant portion of agricultural loss. It is thus crucial to develop strategies to delay this physiological process. Melatonin, an extensively studied molecule, has been demonstrated to play a role in the regulation of leaf senescence in plants. Here, we report the role of exogenous melatonin in the alleviation of methyl jasmonate (MeJA)-induced senescence in tomato (Solanum lycopersicum) leaves. The application of melatonin led to slower degradation of chlorophyll, reduced electrolyte leakage, decreased malondialdehyde (MDA) content, and reduced reactive oxygen species (ROS) levels in tomato leaves incubated with MeJA. In addition, melatonin repressed the upregulation of senescence-related genes (SAG and SEN) and chlorophyll degradation genes (SGR1 and PAO) in tomato leaves exposed to MeJA. Furthermore, melatonin stimulated the activity of a Calvin-Benson Cycle enzyme sedoheptulose-1,7-bisphosphatase (SBPase) and alleviated the inhibition of SlSBPASE (tomato SBPase gene) expression and in MeJA-treated tomato leaves, suggesting an action of melatonin on the capacity for carbon fixation during senescence. Collectively, these results support a role for melatonin in the alleviation of MeJA-induced senescence in tomato leaves. This work also presents a case study that melatonin may be a useful agent in the delay of crop senescence in agricultural practice.
Highlights
Senescence is the final stage of leaf development and is highly regulated by internal factors, such as developmental age and hormone level, and environmental factors, including drought, heat, dark, nutrient deficiency, and UV-B irradiation [1]
Melatonin repressed the upregulation of senescence-related genes (SAG and SEN) and chlorophyll degradation genes (SGR1 and PAO) in tomato leaves exposed to methyl jasmonate (MeJA)
We found that exogenous melatonin slowed down chlorophyll degradation, reduced electrolyte leakage, and decreased the inhibition of photosynthetic capacity in MeJA-treated tomato leaves
Summary
Senescence is the final stage of leaf development and is highly regulated by internal factors, such as developmental age and hormone level, and environmental factors, including drought, heat, dark, nutrient deficiency, and UV-B irradiation [1]. During senescence, the expression of senescence-associated genes is largely boosted, while the expression of photosynthesis-related genes is dramatically down regulated [2,3,4,5] Another important characteristic of leaf senescence is the excessive accumulation of reactive oxygen species (ROS) caused by an imbalance between production and scavenging of ROS [6,7]. It is an evolutionarily developmental process important for optimal production of offspring and survival of plants under some unfavorable environmental conditions, leaf senescence limits growth and yields in crops, leading to a significant portion of agricultural loss. It is crucial to understand this physiological process so as to develop strategies to control and delay this process
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