Page 132 - PC2019 Program & Proceedings

PLANT CANADA 2019

S49. Comparative study of grapevine red blotch virus (GRBV) pcr detection methods and their
application to a general lab practice
Kim, W-S.
Norgen Biotek Corp.

Grapevine Red Blotch Virus (GRBV) is a devastating DNA virus causing significant economic impacts
on grape industries. GRBV infected vines result in reduction of sugar accumulation, uneven ripening and
red color development. Only PCR based detection methods have been adapted as primary detection
methods since no antibody has been available for ELISA detection. A comparative study between end-
point PCR and Real-Time PCR (TaqMan®) methods indicated that Real-Time PCR could detect GRBV
at a higher sensitivity level from different grape varieties. Along with the Real-Time PCR method,
practical lab techniques for PCR control, robust and consistent GRBV isolation, sample collection
strategy and quantification of GRBV infection were established. We also discovered a Real-Time PCR
method as a screening tool for GRBV genetic variance found in Ontario.

Won-Sik Kim (wonsik.kim@norgenbiotek.com)

S50. Improvement of biomass digestibility through the manipulation of tricin biosynthesis pathway
in rice
2
2
1
2
1
Lo, C ; P. Ying ; A.C.W. Lui ; L. Wang ; T. Umezawa ; Y. Tobimatsu
1
1 The University of Hong Kong
2 Kyoto University
Plant biomass is an abundant and sustainable raw material for biofuel ethanol production. However, the
presence of lignin in cell wall impedes the release of sugar from cellulose for fermentation. Lignin is
derived from oxidative couplings of monolignols. Interestingly, a wide range of monocots utilize tricin (a
3’, 5’-dimethoxyflavone) as a natural co-monomer with monolignols for lignification. Following the
characterization of two P450 enzymes CYP93G1 and CYP75B4, we finalized the tricin biosynthesis
pathway in rice as naringenin → apigenin → luteolin → chrysoeriol → selgin → tricin. CYP93G1 is a
flavone synthase II which introduces the C2=C3 double bond to naringenin to form apigenin. Meanwhile,
CYP75B4 serves a dual functional enzyme with apigenin 3’-hydroxylase and chrysoeriol 5’-hydroxylase
activities. Importantly, both CYP93G1 and CYP75B4 are indispensable for generating tricin monomer for
lignification. The respective rice mutants showed wild-type growth phenotypes with intact vascular
tissues while NMR analysis demonstrated the depletion of tricin in cell wall lignin. Furthermore, both
mutants showed reduced lignin content, altered S/G ratio, and enhanced enzymatic saccharification
efficiency in biomass. Hence, genetic manipulation of tricin biosynthesis represents an attractive strategy
to engineer grass lignin for improved biomass utilization without severely compromising plant fitness.
Given that CYP93G1 and CYP75B4 are highly conserved in Poaceae, there is a strong potential to extend
the application to bioenergy grass crops and other cereal crop residues.

Clive Lo (clivelo@hku.hk)

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