Ty3/gypsy-like retrotransposon knockout of a 2-methyl-6-phytyl-1,4-benzoquinone methyltransferase is non-lethal, uncovers a cryptic paralogous mutation, and produces novel tocopherol (vitamin E) profiles in sunflower
Sunflower (Helianthus annuus L.) seeds have a tocopherol profile dominated by alpha-tocopherol. The objective of this research was to study the dynamics of tocopherol accumulation in sunflower lines with altered total tocopherol content or tocopherol profile. Developing seeds were sampled at regular intervals in two lines with reduced and increased total tocopherol content, respectively, and six lines with modified tocopherol profiles. The line with reduced tocopherol content showed a tocopherol accumulation rate reduced by half, whereas the line with increased tocopherol content showed a tocopherol accumulation rate twofold higher than the control. In the three cases, alpha-tocopherol followed a sigmoid accumulation pattern. Modified tocopherol profiles were expressed at early stages of tocopherol accumulation. In most lines with modified profiles, tocopherol accumulation pattern differed from the alpha-tocopherol lines, with maximum tocopherol content at 18 or 21 days after flowering (DAF) that was reduced to reach a plateau from 33 or 36 DAF onward. Such a reduction was caused by continued dry matter accumulation after tocopherol accumulation ceased or slowed down. In lines with increased levels of beta-tocopherol or both gamma- and delta-tocopherol, the synthesis of beta- and delta-tocopherol started and stopped earlier than the synthesis of alpha- and gamma-tocopherol, respectively.