Characterization of a sweet basil acyltransferase involved in eugenol biosynthesis

The sweet basil glandular trichome-enriched BAHD acyltransferase CAAT1 involved in eugenol formation was characterized. RNAi of CAAT1 leads to a decrease in eugenol and accumulation of coniferyl alcohol and its derivatives.  Abstract Sweet basil (Ocimum basilicum) plants produce its characteristic p...

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Bibliographic Details
Published in:Journal of experimental botany 2020-06, Vol.71 (12), p.3638-3652
Main Authors: Dhar, Niha, Sarangapani, Sreelatha, Reddy, Vaishnavi Amarr, Kumar, Nadimuthu, Panicker, Deepa, Jin, Jingjing, Chua, Nam-Hai, Sarojam, Rajani
Format: Article
Language:English
Subjects:
Acyltransferases - genetics
Eugenol
Ocimum basilicum - genetics
Plant Leaves
Research Papers
Trichomes
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Summary:The sweet basil glandular trichome-enriched BAHD acyltransferase CAAT1 involved in eugenol formation was characterized. RNAi of CAAT1 leads to a decrease in eugenol and accumulation of coniferyl alcohol and its derivatives.  Abstract Sweet basil (Ocimum basilicum) plants produce its characteristic phenylpropene-rich essential oil in specialized structures known as peltate glandular trichomes (PGTs). Eugenol and chavicol are the major phenylpropenes produced by sweet basil varieties whose synthetic pathways are not fully elucidated. Eugenol is derived from coniferyl acetate by a reaction catalysed by eugenol synthase. An acyltransferase is proposed to convert coniferyl alcohol to coniferyl acetate which is the first committed step towards eugenol synthesis. Here, we perform a comparative next-generation transcriptome sequencing of different tissues of sweet basil, namely PGT, leaf, leaf stripped of PGTs (leaf–PGT), and roots, to identify differentially expressed transcripts specific to PGT. From these data, we identified a PGT-enriched BAHD acyltransferase gene ObCAAT1 and functionally characterized it. In vitro coupled reaction of ObCAAT1 with eugenol synthase in the presence of coniferyl alcohol resulted in eugenol production. Analysis of ObCAAT1-RNAi transgenic lines showed decreased levels of eugenol and accumulation of coniferyl alcohol and its derivatives. Coniferyl alcohol acts as a common substrate for phenylpropene and lignin biosynthesis. No differences were found in total lignin content of PGTs and leaves of transgenic lines, indicating that phenylpropene biosynthesis is not coupled to lignification in sweet basil.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/eraa142