Metabolic and histopathological alterations of Jatropha mosaic begomovirus-infected Jatropha curcas L. by HR-MAS NMR spectroscopy and magnetic resonance imaging

Alterations in the anatomical structures, sap translocation and metabolic profiles in Jatropha curcas L. (Euphorbiaceae), infected with Jatropha mosaic virus (JMV) have been investigated using MRI and HR-MAS NMR spectroscopy. The contrast of MRI images distinguishes abnormalities in anatomical structures of infected and healthy stem. The HR-MAS NMR spectroscopic analysis indicated that viral infection significantly affected the plant metabolism. Higher accumulation of TCA cycle intermediates, such as citrate and malate, in JMV-infected plants suggested a higher rate of respiration. The respiration rate was more than twofold as compared to healthy ones. The viral stress also significantly increases the concentrations of alanine, arginine, glutamine, valine, GABA and choline as compared to healthy ones. Microscopic examination revealed severe hyperplasia caused by JMV with a considerable reduction in the size of stem cells. Lower concentration of glucose and sucrose in viral-infected stem tissues indicates decreased translocation of photosynthates from leaves to stem due to hyperplasia caused by JMV. The MR images distinguished stele, cortical and pith regions of JMV-infected and healthy stems. Contrast of T1- and T2-weighted images showed significant differences in the spatial distribution of water, lipids and macromolecules in virus-infected and healthy stem tissues. The results demonstrated the value of MRI and HR-MAS NMR spectroscopy in studying viral infection and metabolic shift in plants. The present methodology may help in better understanding the metabolic alterations during biotic stress in other plant species of agricultural and commercial importance.