Abstract
The physiological functions of sphingolipids in animals have been intensively studied, while less attention has been paid to their roles in plants. Here, we reveal the involvement of sphingolipid delta8 desaturase (SlSLD) in the chilling resistance of tomato (Solanum lycopersicum cv. Micro-Tom). We used the virus-induced gene silencing (VIGS) approach to knock-down SlSLD expression in tomato leaves, and then evaluated chilling resistance. Changes in leaf cell structure under a chilling treatment were observed by transmission electron microscopy. In control plants, SlSLD was highly expressed in the fruit and leaves in response to a chilling treatment. The degree of chilling damage was greater in SlSLD-silenced plants than in control plants, indicating that SlSLD knock-down significantly reduced the chilling resistance of tomato. Compared with control plants, SlSLD-silenced plants showed higher relative electrolytic leakage and malondialdehyde content, and lower superoxide dismutase and peroxidase activities after a chilling treatment. Chilling severely damaged the chloroplasts in SlSLD-silenced plants, resulting in the disruption of chloroplast membranes, swelling of thylakoids, and reduced granal stacking. Together, these results show that SlSLD is crucial for chilling resistance in tomato.
Highlights
Besides playing structural roles in cellular membranes, sphingolipids function as bioactive signaling molecules in the regulation of cell growth, differentiation, senescence, and apoptosis in mammals[8]
To identify chilling stress-responsive genes related to sphingolipid metabolism, the transcript levels of SlSLD, long chain base hydroxylase, long chain base-1-phosphate lyase, sphingolipid delta-4 desaturase, neutral ceramidase, long chain base kinase, ceramide synthase, and glucosylceramide synthase were analyzed in tomato exposed to a 6-h chilling treatment
The transcript levels of SlSLD1 were increased 23.4-fold in leaves and 2.9-fold in fruit, and the transcript levels of SlSLD2 were increased 8.4-fold in leaves and 2.4-fold in fruit. These results suggested that SlSLD1 and 2 are important chilling stress-responsive genes involved in sphingolipid metabolism
Summary
Besides playing structural roles in cellular membranes, sphingolipids function as bioactive signaling molecules in the regulation of cell growth, differentiation, senescence, and apoptosis in mammals[8]. Sphingolipids have been proposed to play important roles in cell signaling[9], membrane homeostasis[10], pathogen resistance[11], and abiotic stress responses[1]. Sphingolipids and their related enzymes have been shown to play roles in aluminum tolerance[12], drought acclimation[13], and resistance to hypoxia[14]. Suppression of SlSLD by virus-induced gene silencing (VIGS) led to a marked decrease in chilling resistance and severe chilling damage to chloroplasts These findings suggested that SlSLD could be a potential target gene in the future to develop chilling-tolerant tomato and other economic crop plants
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