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Virus‐induced gene silencing identifies C atharanthus roseus 7‐deoxyloganic acid‐7‐hydroxylase, a step in iridoid and monoterpene indole alkaloid biosynthesis
Author(s) -
Salim Vonny,
Yu Fang,
Altarejos Joaquín,
Luca Vincenzo
Publication year - 2013
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 - 10.1111/tpj.12330
Subject(s) - iridoid , biology , biosynthesis , biochemistry , hydroxylation , gene silencing , catharanthus roseus , gene , enzyme , botany , glycoside
Summary Iridoids are a major group of biologically active molecules that are present in thousands of plant species, and one versatile iridoid, secologanin, is a precursor for the assembly of thousands of monoterpenoid indole alkaloids ( MIA s) as well as a number of quinoline alkaloids. This study uses bioinformatics to screen large databases of annotated transcripts from various MIA ‐producing plant species to select candidate genes that may be involved in iridoid biosynthesis. Virus‐induced gene silencing of the selected genes combined with metabolite analyses of silenced plants was then used to identify the 7‐deoxyloganic acid 7‐hydroxylase ( C r DL 7 H ) that is involved in the 3rd to last step in secologanin biosynthesis. Silencing of CrDL7H reduced secologanin levels by at least 70%, and increased the levels of 7‐deoxyloganic acid to over 4 mg g − 1 fresh leaf weight compared to control plants in which this iridoid is not detected. Functional expression of this CrDL7H in yeast confirmed its biochemical activity, and substrate specificity studies showed its preference for 7‐deoxyloganic acid over other closely related substrates. Together, these results suggest that hydroxylation precedes carboxy‐O‐methylation in the secologanin pathway in C atharanthus roseus .