Constitutive Expression of AtVTE2 in Flax Is Associated with Changes in Isoprenoid Metabolism and Stem Cell-Wall Composition.

Tocopherols are essential lipid-soluble antioxidants that play important roles in plant protection against oxidative stress and are closely connected with isoprenoid metabolism. To the best of our knowledge, this is the first report of stable constitutive expression of Arabidopsis thaliana VTE2 (AtVTE2) in flax (Linum usitatissimum L.) and its effects on plant metabolism and development. As a dual-purpose oil and fibre crop, flax combines PUFA-rich seeds with industrially important fibre-rich stems, providing a useful system for assessing the broader consequences of antioxidant-pathway engineering. Three independent transgenic lines were characterized by RT-qPCR analysis of genes associated with tocopherol, MEP, MVA, and carotenoid biosynthesis, targeted metabolite profiling, antioxidant-capacity assays, field phenotyping, and biochemical and spectroscopic analyses of mature straw. Three independent transgenic lines were characterized using gene-expression analyses, metabolic profiling, antioxidant assays, phenotypic evaluation, and biochemical analyses of mature stems. Constitutive AtVTE2 expression was associated with α-tocopherol accumulation and was accompanied by coordinated transcriptional changes in genes associated with the plastidial methylerythritol phosphate and cytosolic mevalonate pathways. These changes were associated with modifications in isoprenoid and phenylpropanoid metabolism, enhanced antioxidant capacity in selected transgenic lines, and altered plant architecture under field conditions. In mature straw, transgenic plants exhibited changes in phytosterol composition, lignin accumulation, and pectin distribution, whereas cellulose content remained unchanged. FT-IR spectra retained the same principal bands but showed differences in the relative intensities of selected cell-wall-associated bands. Collectively, these findings demonstrate that constitutive AtVTE2 expression is associated with tissue-dependent metabolic responses extending beyond vitamin E accumulation and affecting interconnected pathways involved in secondary metabolism, antioxidant capacity, and cell-wall organization.