| Budget Amount *help |
¥14,100,000 (Direct Cost: ¥14,100,000)
Fiscal Year 2002: ¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2001: ¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2000: ¥8,200,000 (Direct Cost: ¥8,200,000)
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| Research Abstract |
In this project, we have tried to isolate and characterize jasmonic acid (JA)-responsive genes to elucidate the signal transduction pathways of JA in suspension-cultured rice cells. In addition, molecular probes for JA receptors were also synthesized.
The JA-responsive genes RRJ1 and RRJ2 were found to encode a putative rice cystathionine γ-lyase and a pyruvate decarboxylase, respectively. RRJ1 is possibly involved in biosynthesis and/or metabolism of sulfur-containing amino acids and related biochemical processes, and RRJ2, in energy metabolism for elicitor-induced defense reactions in suspension-cultured rice cells.
We succeeded in cloning of the JA-responsive gene OsOPR1 encoding 12-oxophytodienoic acid (OPDA) reductase (OPR) that is one of key biosynthetic enzymes of JA. This is the first cloning of an OPR gene from a monocot plant. Since OsOPR1 catalyze reduction of (-)-cis-OPDA preferentially over (+)-cis-OPDA, a natural precursor of JA, OsOPR1 might contribute to other physiologic
… More
al phenomena than JA biosynthesis.
RERJ1 was isolated as an early JA-responsive gene which encodes a transcriptional regulator possessing a basic region/helix-loop-helix motif. Based on analysis of phenotypes of sense- or antisense-RERJ1 mRNA overexpressing transgenic rice plants, RERJ1 is suggested to be involved in JA-induced inhibition of shoot growth in rice. Involvement of RERJ1 in other physiological phenomena including defense response is also quite possible. Futher analysis of biological functions of RERJ1 is in progress.
JA functions as a key signal transducer in a chitin elicitor-induced diterpenoid phytoalexin production in suspension-cultured rice cells. We isolated a cDNA encoding a diterpene cyclase from the chitin-elicited suspension-cultured rice cells, and demonstrated that the gene product functioned as ent-cassa-12, 15-diene synthase. This is the first report of isolation of a cDNA encoding a diterpene cyclase involved in biosynthesis of a diterpene hydrocarbon which is a putative precursor of diterpenoid phytoalexins in rice. ent-Cassa-12, 15-diene synthase cDNA isolated here will be a useful tool to investigate the regulatory mechanisms of biosynthesis of the rice diterpenoid phytoalexins (-)-phytocassanes during plant development and by change of environmental conditions.
We synthesized several types of JA derivatives including JA-amino acid conjugates, JA-biotin conjugate, JA-dexamethasone heterodimer, and JA-fluoresceine conjugate as candidates for molecular probes for JA-binding proteins. Since these synthesized compounds except JA-fluoresceine conjugate exhibited significant JA-like activities in rice seedling assay, soybean PAL-inducing assay, and/or rice momilactone A-inducing assay, they might be useful probes to isolate and characterize JA-binding proteins. Less
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