Reference "Biological functions of ent- and syn-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis"

Reference ID

11684

Title

Biological functions of ent- and syn-copalyl diphosphate synthases in rice: key enzymes for the branch point of gibberellin and phytoalexin biosynthesis

Source

The Plant journal : for cell and molecular biology, 2004, vol. 39, pp. 886-893

Authors (9)

Otomo-K	Kenmoku-H
Oikawa-H	Konig-W-A
Toshima-H	Mitsuhashi-W
Yamane-H	Sassa-T
Toyomasu-T

Abstract

Rice (Oryza sativa L.) produces ent-copalyl diphosphate (ent-CDP) and syn-CDP as
precursors for several classes of phytoalexins and the phytohormones,
gibberellins (GAs). It has recently been shown that a loss-of-function mutation
of OsCPS1, a gene encoding a putative ent-CDP synthase, results in a severely
GA-deficient dwarf phenotype in rice. To clarify the biological functions of the
ent- and syn-CDP synthases involved in the biosynthesis of phytoalexins and/or
GAs, we isolated two cDNAs, OsCyc1 and OsCyc2, encoding putative diterpene
cyclases from ultraviolet (UV)-irradiated rice leaves (cv. Nipponbare). The
production of phytoalexins in rice leaves is known to be highly induced by UV
treatment. Using a bacterial expression system, we demonstrated that OsCyc1
encodes syn-CDP synthase and that OsCyc2 and OsCPS1 encode ent-CDP synthase. The
level of expression of the OsCyc1 and OsCyc2 transcripts in rice leaves
increased drastically in response to UV treatment, whereas expression of the
OsCPS1 transcript was not induced by UV light. These results suggest that
OsCyc1, OsCyc2 and OsCPS1 are responsible for the biosynthesis of momilactones A
and B and oryzalexin S, oryzalexins A-F and phytocassanes A-E, and GAs,
respectively. Our results strongly suggest the presence of two ent-CDP synthase
isoforms in rice, one that participates in the biosynthesis of GAs and a second
that is involved in the biosynthesis of phytoalexins.