Melatonin alleviates drought stress in linseed (Linum usitatissimum L.) by regulating antioxidants and LusCYP450 encoding genes

• The chlorophyll content and chlorophyll fluorescence was recorded as increased by MT application under both non-stress and drought stress conditions. • MT was able to mitigate the harmful effect of drought by inhibiting the access reactive oxygen species (ROS) production and activating antioxidant defense system. • 57 CYP-450 encoding genes have been identified in linseed genome and well characterized. • LusCYP450-25 and LusCYP450-38 was found most regulated and highly expressed candidate genes which showed MT induced response under drought stress. Linseed is an important minor oilseed crop. It is grown in rainfed and irrigated ecologies. Drought is a major concern in rainfed cultivation which leads to severe yield penalty depending on duration and severity of stress especially at seedling establishment stage. Melatonin (MT) has emerged as a non toxic signaling molecule, which regulates plant growth and improves stress tolerance. The present study was carried out to examine the protective role of MT on physiological, biochemical and molecular processes under drought stress. The results indicated that drought stress strongly suppressed the growth and other physiological traits like chlorophyll content, membrane stability index (MSI), relative water content (RWC), etc. MT was able to mitigate the harmful effect of drought by inhibiting the excess reactive oxygen species (ROS) production and activating antioxidant defense system. Identification and characterization of CYP450 candidate genes in linseed showed significant diversity in its structure and possible function. The gene expression profile of key candidates under drought stress demonstrated the induction of gene expression by MT which alleviates the drought stress.