Page 274 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

enzymes were also detected in the cytoplasmic fraction. A model for the cellular localization of mescaline
biosynthesis in peyote will be presented.

[P141] A UNIQUE PATHOGEN-INDUCIBLE STILBENE O-METHYLTRANSFERASE IN SORGHUM.
Nan Lin , Andy CW Lui , Lydia PY Lam , Yuki Tobimatsu , Guoquan Liu , Ian Godwin , Lanxiang
3
1
1,2
5
5
4
1 1
6
Wang , and Clive Lo . School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong
Kong, China; Present address: Plant Breeding and Genetics Section, School of Integrative Plant
2
3
Science, Cornell University, Ithaca, NY14853, USA; Center for Crossover Education, Graduate School of
Engineering Science, Akita University, Tegata Gakuen-machi 1-1, Akita City, Akita 010-8502, Japan;
4 Research Institute for SustainableHumanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011,
Japan; Queensland Alliance for Agriculture and Food Innovation, The University of Queensland,
5
Brisbane, QLD 4072, Australia; and CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen
6
Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of
Sciences, Shenzhen 518055, China.
Correspondence to: nanlin98@connect.hku.hk

Stilbenes are characterized by the 1,2 -diphenylethylene nucleus. They belong to a small family of plant-
specialized metabolites which have been extensively investigated for their valuable pharmaceutical
effects and antimicrobial activities. Simple stilbenes can be glycosylated, methylated, or oligomerized by
specific enzymes, giving rise to different structural derivatives. Notably, O-methylated stilbenes produced
by methylation of a hydroxyl group are prominent nutraceuticals but rarely produced by crop plants.

In this study, several stilbene compounds including resveratrol, piceid (resveratrol 3-O-glucoside), and O-
methylated resveratrol derivatives, i.e. pinostilbene (3-O-methylated stilbene) and pterostilbene (3,5-bis-
O-methylated resveratrol), were detected in sorghum seedlings following infection by the anthracnose
pathogen Colletotrichum sublineola. In particular, the resistant genotype SC748-5 accumulated 9 times
more pterostilbene than the susceptible genotype BTx623. In vitro spore germination and mycelial growth
assays further demonstrated the superior inhibitory effects of pterostilbene over pinostilbene and
resveratrol towards C. sublineolum, highlighting the importance of stilbene O-methylations during defense
responses in sorghum.

In silico expression dataset for Bipolaris sorghicola-infected sorghum leaves and our in-house
transcriptome dataset for C. sublineola-infected sorghum seedlings were analyzed. Two pathogen-
inducible O-methyltransferase (OMT) genes, SbSOMT (Sb07g004710) and SbOMT4 (Sb07g004590),
potentially involved in stilbene O-methylation were identified. In recombinant enzyme assays, SbSOMT
converted resveratrol to pinostilbene and pterostilbene successively while SbOMT4 showed minimal
SOMT activity. Transient co-expression of SbSOMT with sorghum stilbene synthase (SbSTS1) genes in
Nicotiana benthamiana resulted in the production of pterostilbene in the agro-infiltrated leaves. To
investigate the in planta role of SbSOMT in planta, sbsomt mutants were generated via CRISPR/CAS 9-
mediated genome editing in sorghum genotype TX430. Following C. sublienola infection, sbsomt mutants
accumulate resveratrol and piceid but not pinostilbene or pterostilbene while wild-type plants accumulate
different both stilbene O-methylated derivatives, hence establishing the indispensable role of SbSOMT in
the O-methylation of resveratrol to form pinostilbene and pterostilbene.

Phylogenetic analysis further revealed that SbSOMT homologs are restricted to Sorghum spp. including
S. bicolor and S. halapense (Johnson grass). Apparently, the genus-specific stilbene O-
methyltransferases were recruited from canonical caffeic acid O-methyltransferases (COMTs) after the
divergence of Sorghum spp. from Saccharum spp.

Overall, our work presents SbSOMT as a unique SOMT that may be exploited for bioengineering of
bioactive O-methylated stilbenes. presents SbOMT as a novel target for bioengineering of stilbene O-
methylation via transgenic technology or synthetic biology.

273