Abstract
The plant cuticle, composed of cutin and waxes, is a hydrophobic layer coating the aerial organs of terrestrial plants and playing a critical role in limiting water loss. While melatonin has been recently demonstrated to be involved in responses to drought stress in plants, its relationship with cuticle formation is not known. In the present work, we report the effects of melatonin on the formation of cuticle in tomato leaves subjected to water deficit. Preliminary analysis by light microscope showed that tomato leaves pretreated with exogenous melatonin might have thicker cutin than tomato leaves without melatonin pretreatment under water deficit condition. Chemical characterization showed that exogenous application of melatonin increased the level of cuticular waxes in tomato leaves under water deficit. Consistent with the change in cuticular waxes was the increased abundance of wax-associated gene transcripts. Further, assessment of water loss and chlorophyll leaching in tomato leaves revealed the association of cuticle deposition with reduced leaf permeability, which is important in restricting water loss in water deficit-stressed tomato plants. These results suggest a role for melatonin in regulating leaf cuticle formation and non-stomatal water loss in leaves.
Highlights
The plant cuticle is a hydrophobic layer covering the outermost surfaces of terrestrial plants.The cuticle consists of cutin and cuticular waxes
The plant cuticle is a ubiquitous layer of land plants, which plays a crucial role in restricting non-stomatal water evaporation
Studies have demonstrated that the increase in cuticles, consisting of cutin and cuticular wax, reduces water loss in leaf [12,13]
Summary
The plant cuticle is a hydrophobic layer covering the outermost surfaces of terrestrial plants. Cutin is a polymer of ester-linked ω-hydroxylated fatty acids, while cuticular wax is a complex mixture of very-long-chain fatty acids (VLCFAs), VLCFA derivatives and secondary metabolites, such as triterpenoids and flavonoids [1,2,3] As it represents the interface with plants and the surrounding environment, the cuticle plays a wide range of roles in plant development and physiological responses to biotic and abiotic stresses. To multiple stresses plants, including cold, heat, salinity, heavy metal and melatonin has been found to play a role in the delay of senescence in plants [24,25].
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