AUTHOR=Georgiadou Egli C. , Ntourou Thessaloniki , Goulas Vlasios , Manganaris George A. , Kalaitzis Panagiotis , Fotopoulos Vasileios 

TITLE=Temporal analysis reveals a key role for VTE5 in vitamin E biosynthesis in olive fruit during on-tree development

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00871

DOI=10.3389/fpls.2015.00871

ISSN=1664-462X

ABSTRACT=<p>The aim of this work was to generate a high resolution temporal mapping of the biosynthetic pathway of vitamin E in olive fruit (<italic>Olea europaea</italic> cv. “Koroneiki”) during 17 successive on-tree developmental stages. Fruit material was collected from the middle of June until the end of January, corresponding to 6–38 weeks after flowering (WAF). Results revealed a variable gene regulation pattern among 6–38 WAF studied and more pronounced levels of differential regulation of gene expression for the first and intermediate genes in the biosynthetic pathway (<italic>VTE5, geranylgeranyl reductase, HPPD, VTE2, HGGT</italic> and <italic>VTE3</italic>) compared with the downstream components of the pathway (<italic>VTE1</italic> and <italic>VTE4</italic>). Notably, expression of <italic>HGGT</italic> and <italic>VTE2</italic> genes were significantly suppressed throughout the developmental stages examined. Metabolite analysis indicated that the first and intermediate stages of development (6–22 WAF) have higher concentrations of tocochromanols compared with the last on-tree stages (starting from 24 WAF onwards). The concentration of α-tocopherol (16.15 ± 0.60−32.45 ± 0.54 mg/100 g F.W.) were substantially greater (up to 100-fold) than those of β-, γ-, and δ-tocopherols (0.13 ± 0.01−0.25 ± 0.03 mg/100 g F.W., 0.13 ± 0.01−0.33 ± 0.04 mg/100 g F.W., 0.14 ± 0.01−0.28 ± 0.01 mg/100 g F.W., respectively). In regard with tocotrienol content, only γ-tocotrienol was detected. Overall, olive fruits (cv. “Koroneiki”) exhibited higher concentrations of vitamin E until 22 WAF as compared with later WAF, concomitant with the expression profile of phytol kinase (<italic>VTE5</italic>), which could be used as a marker gene due to its importance in the biosynthesis of vitamin E. To the best of our knowledge, this is the first study that explores the complete biosynthetic pathway of vitamin E in a fruit tree crop of great horticultural importance such as olive, linking molecular gene expression analysis with tocochromanol content.</p>