Reduction of the geomagnetic field to hypomagnetic field modulates tomato (Solanum lycopersicum L. cv Microtom) gene expression and metabolomics during plant development

An interesting aspect that links the geomagnetic field (GMF) to the evolution of life lies in how plants respond to the reduction of the GMF, also known as hypomagnetic field (HMF). In this work, tomato plants (Solanum lycopersicum cv Microtom) were exposed either to GMF or HMF and were studied during the development of leaves and fruit set. Changes of expression of genes encoding for primary and secondary metabolites, including Reactive Oxygen Species (ROS), proteins, fatty acids, polyphenols, chlorophylls, carotenoids and phytohormones were assessed by qRT-PCR, while the corresponding metabolite levels were quantified by GC-MS and HPLC-MS. Two tomato homologs of the fruit fly magnetoreceptor MagR, Isca-like 1 and erpA 2, were modulated by HMF, as were numerous tomato genes under investigation. In tomato leaves, positive correlations were observed with most of the genes associated with phytohormones production, ROS scavenging and production, and lipid metabolism, whereas an almost reversed trend was found in flowers and fruits. Interestingly, downregulation of Isca-like 1 and erpA 2 was found to correlate with an upregulation of most unripe fruit genes. Exposure to HMF reduced chlorophyll and carotenoid content, decreased photosynthetic efficiency and increased non-photochemical quenching. Auxins, gibberellins, cytokinins, abscisic acid, jasmonic acid and salicylic acid content and the expression of genes related to their metabolism correlated with tomato ISCA modulation. The results here reported suggest that Isca-like 1 and erpA 2 might be important players in tomato magnetoreception.