Grant-in-Aid for Scientific Research (A)
|Allocation Type||Single-year Grants|
|Research Institution||Okayama University|
SHIRAISHI Tomonori Okayama University, Faculty of Agriculture, Professor, 農学部, 教授 (10033268)
ICHINOSE Yuki Okayama University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (50213004)
YAMADA Tetsuji Okayama University, Faculty of Agriculture, Professor, 農学部, 教授 (00191320)
|Project Period (FY)
1994 – 1996
Completed(Fiscal Year 1996)
|Budget Amount *help
¥29,300,000 (Direct Cost : ¥29,300,000)
Fiscal Year 1996 : ¥4,700,000 (Direct Cost : ¥4,700,000)
Fiscal Year 1995 : ¥5,800,000 (Direct Cost : ¥5,800,000)
Fiscal Year 1994 : ¥18,800,000 (Direct Cost : ¥18,800,000)
|Keywords||resistance / signal transduction / defense response / elicitor / suppressor / host-parasite specificity / gene regulation / cis-trans / 防御応答 / 情報伝達 / 防御遺伝子発現制御 / 細胞壁 / クロストーク / エンドウ褐紋病菌 / シグナル伝達機構 / ATPase / ポリホスホイノシチド代謝系 / リセプター|
In this study, we attempted to clarify the molecular mechanisms in the signal transduction cascade between perception of fungal signal molecules and the expression of defense responsive genes.
Our findings are summarized as follows :
1. ATPase and polyphosphoinositide metabolism in pea plasma membranes are regulated by the clicitor and suppressor from Mycosphaerella pinodes. The suppressor, however, blocked nonspecifically them even in plasma membranes isolated from non-host plants of the fungus.
2. The M.pinodes-elcitor enhanced nonspecifically the activities of ATPase (NTPase), peroxidase and ascorbic acid oxidase in NaCl-soluble fraction from cell walls isolated from pea and cowpea, whereas the suppressor blocked these activities in a species-specific manner.
3. Superoxide anion and as yet unidentified infection-inhibitor, that were generated in isolated pea cell wall by the elicitor, were inhibited by the suppressor. On the other hand, those in cowpea cell wall were inversely elicited
by the suppressor alone.
4. Signal transduction leading to phytoalexin production was mediated by connection of certain vitronectin-like molecules in cell wall and vitronectin receptor-like molecules on plasma membrane.
5. In the promoter sequence of PSPALs and PSCHSs, we found conserved sequence motifs, such as Box-1 (homologous to Box L), Box-2 (homologous to Box P) and Box-4 (AT-box) that were essential for response to the elicitor.
6. In PSCHSL the directly repeated AT-rich sequences, TAAAATACT were capable of forming a low mobility complex (LMC) by a gel mobility shift assay and in vitro DNase i-footprinting analysis. The finding, that treatment of the nuclear factors with alkaline phosphatase abolished LMC formation, indicates phosphorylation of nuclear protein (s) is necessary for the formaiton of complex machinery.
7. The cis-elements such as Box1, Box2 and G-box were essential for the promoter of elicitor-responsive CHS genes.
From these results, we propose the stream of signal transduction leading to defense responses as follows : 1) signal molecules are percepted by respective receptors on cell wall ; 2) the second messengers are carried out into the cells via vitronectin receptor-like proteins on the plasma membranes ; 3) polyphosphoinositide metabolism in plasma membranes is also activated to produce the 3rd messenger ; 4) the messenger stimulates phosphorylation of nuclear factor (s) ; 5) The transcription of defense responsive genes are activated ; 6) the rejection reaction is expressed in the clicitor-treated plant tissues. Less