Open AccessCharacterization of a sweet basil acyltransferase involved in eugenol biosynthesis
Author(s) -
Niha Dhar,
Sreelatha Sarangapani,
Vaishnavi Amarr Reddy,
Nitin Kumar,
Deepa Panicker,
Jingjing Jin,
NamHai Chua,
Rajani Sarojam
Publication year - 2020
Publication title -
journal of experimental botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.616
H-Index - 242
eISSN - 1460-2431
pISSN - 0022-0957
DOI - 10.1093/jxb/eraa142
Subject(s) - eugenol , coniferyl alcohol , sweet basil , monolignol , chemistry , cinnamyl alcohol , biosynthesis , phenylpropanoid , methyl jasmonate , methyl eugenol , biochemistry , botany , ocimum , biology , basilicum , cinnamaldehyde , enzyme , organic chemistry , gene , catalysis , pest analysis , tephritidae
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.