Myo-inositol Oxygenase Overexpression Rescues Vitamin C Deficient Arabidopsis (vtc) Mutants

Abstract Biosynthesis of l -ascorbate (AsA) in plants is carried out by a complex metabolic network, which involves d -mannose/ l -galactose, d -galacturonate, l -gulose, and myo -inositol as main precursors. Arabidopsis lines over-expressing enzymes in the myo -inositol pathway have elevated AsA, accumulate more biomass of both aerial and root tissues, and are tolerant to abiotic stresses as shown by manual and digital phenotyping. We crossed myo -inositol oxygenase ( MIOX4 ) over-expressers with two low-vitamin C mutants ( vtc 1-1 and vtc 2-1) encoding enzymes involved in d -mannose/ l -galactose route. The purpose of developing these crosses was to test MIOX4’s ability to restore the low AsA phenotype in mutants, and to assess the contribution of individual biosynthetic pathways to abiotic stress tolerance. We used a powerful high-throughput phenotyping platform for detailed phenotypic characterization of the Arabidopsis crosses with visible, fluorescence, near-infrared and infrared sensors. We combined digital phenotyping with photosynthetic parameters and soil water potential measurements. Our results show that MIOX4 is able to restore the AsA content of the mutants and the restored lines (vtc+MIOX4) show high AsA, enhanced growth rate, accumulate more biomass, and display healthier chlorophyll fluorescence and water content profiles compared to controls. Highlights Constitutive expression of a myo -inositol oxygenase restored vitamin C deficient ( vtc mutants). The restored lines have elevated ascorbate content and are tolerant to abiotic stresses. Under normal and abiotic stress conditions, the restored lines have enhanced biomass and increased water retention.