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1‐Deoxy‐ d ‐xylulose 5‐phosphate reductoisomerase and plastid isoprenoid biosynthesis during tomato fruit ripening
Author(s) -
RodríguezConcepción Manuel,
Ahumada Iván,
DiezJuez Ester,
SauretGüeto Susanna,
Lois Luisa María,
Gallego Francesca,
CarreteroPaulet Lorenzo,
Campos Narciso,
Boronat Albert
Publication year - 2001
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2001.01089.x
Subject(s) - plastid , carotenoid , ripening , biosynthesis , biochemistry , chromoplast , phytoene , terpenoid , biology , atp synthase , phytoene synthase , enzyme , mutant , botany , chloroplast , gene
Summary The recently discovered 2‐ C ‐methyl‐ d ‐erythritol 4‐phosphate (MEP) pathway for the biosynthesis of plastid isoprenoids (including carotenoids) is not fully elucidated yet despite its central importance for plant life. It is known, however, that the first reaction completely specific to the pathway is the conversion of 1‐deoxy‐ d ‐xylulose 5‐phosphate (DXP) into MEP by the enzyme DXP reductoisomerase (DXR). We have identified a tomato cDNA encoding a protein with homology to DXR and in vivo activity, and show that the levels of the corresponding DXR mRNA and encoded protein in fruit tissues are similar before and during the massive accumulation of carotenoids characteristic of fruit ripening. The results are consistent with a non‐limiting role of DXR, and support previous work proposing DXP synthase (DXS) as the first regulatory enzyme for plastid isoprenoid biosynthesis in tomato fruit. Inhibition of DXR activity by fosmidomycin showed that plastid isoprenoid biosynthesis is required for tomato fruit carotenogenesis but not for other ripening processes. In addition, dormancy was reduced in seeds from fosmidomycin‐treated fruit but not in seeds from the tomato yellow ripe mutant (defective in phytoene synthase‐1, PSY1), suggesting that the isoform PSY2 might channel the production of carotenoids for abscisic acid biosynthesis. Furthermore, the complete arrest of tomato seedling development using fosmidomycin confirms a key role of the MEP pathway in plant development.