Sweet Basil Has Distinct Synthases for Eugenol Biosynthesis in Glandular Trichomes and Roots with Different Regulatory Mechanisms

• Published in: International journal of molecular sciences Vol. 22; no. 2; p. 681
• Main Authors: Reddy, Vaishnavi Amarr, Li, Chunhong, Nadimuthu, Kumar, Tjhang, Jessica Gambino, Jang, In-Cheol, Rajani, Sarojam
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 12-01-2021; MDPI
• Subjects: Alcohol; Amino Acid Sequence; Binding sites; Bioinformatics; Biosynthesis; Enzymes; Eugenol; Eugenol - chemistry; Eugenol - metabolism; eugenol synthase; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Immunohistochemistry; Metabolites; Nicotiana - physiology; Ocimum basilicum; Ocimum basilicum - chemistry; Ocimum basilicum - physiology; Oxidoreductases Acting on CH-CH Group Donors - chemistry; Oxidoreductases Acting on CH-CH Group Donors - genetics; Oxidoreductases Acting on CH-CH Group Donors - metabolism; phenylpropene; Phosphorylation; Plant Leaves - chemistry; Plant Leaves - enzymology; Plant Leaves - metabolism; Plant Physiological Phenomena; Plant Roots - enzymology; Post-translation; post-translational modifications; Promoter Regions, Genetic; Reductases; Regulatory Sequences, Nucleic Acid; Roots; secondary metabolism; sweet basil; Transcription; Trichomes; Trichomes - enzymology; sweet basil; eugenol synthase; post-translational modifications; phenylpropene; phosphorylation; secondary metabolism
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms22020681

Production of a volatile phenylpropene; eugenol in sweet basil is mostly associated with peltate glandular trichomes (PGTs) found aerially. Currently only one eugenol synthase (EGS), ObEGS1 which belongs to PIP family is identified from sweet basil PGTs. Reports of the presence of eugenol in roots led us to analyse other EGSs in roots. We screened for all the PIP family reductase transcripts from the RNA-Seq data. In vivo functional characterization of all the genes in
showed their ability to produce eugenol and were termed as
. Among all,
displayed highest expression in PGTs and
in roots. Further, eugenol was produced only in the roots of soil-grown plants, but not in roots of aseptically-grown plants. Interestingly, eugenol production could be induced in roots of aseptically-grown plants under elicitation suggesting that eugenol production might occur as a result of environmental cues in roots. The presence of
transcript and protein in aseptically-grown plants indicated towards post-translational modifications (PTMs) of ObEGS4. Bioinformatics analysis showed possibility of phosphorylation in ObEGS4 which was further confirmed by in vitro experiment. Our study reveals the presence of multiple eugenol synthases in sweet basil and provides new insights into their diversity and tissue specific regulation.