Journal
PROTOPLASMA
Volume 249, Issue 1, Pages 187-195Publisher
SPRINGER WIEN
DOI: 10.1007/s00709-011-0277-2
Keywords
Auxin; Calcium; Lateral roots; Nitric oxide; Oryza sativa L.
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Funding
- National Science Council of the Republic of China
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In the present study, the role of nitric oxide (NO) in the regulation of lateral root (LR) formation in rice was examined. Application of sodium nitroprusside (SNP; a NO donor) and indole-3-butyric acid (IBA; a naturally occurring auxin) to rice seedlings induced LR formation. The effect is specific for NO because the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3- oxide (cPTIO) blocked the action of SNP and IBA. Endogenous NO was detected by the specific fluorescence probe 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate. SNP- and IBA-induced NO fluorescence was specifically suppressed by cPTIO. Nitrate reductase (NR) inhibitor sodium tungstate completely inhibited IBA-induced LR formation and NO fluorescence. However, nitric oxide synthase inhibitor N (G)-nitro-l-arginine methyl ester hydrochloride slightly reduced IBA-induced LR formation and NO generation. It appears that NO generation that occurs in response to IBA might primarily involve NR activity. Moreover, NO production caused by SNP and IBA was localized in root area corresponding to LR emergence. The effects of Ca2+ chelators, Ca2+-channel inhibitors, and calmodulin antagonists on LR formation induced by SNP and IBA were also examined. All these inhibitors were effective in reducing the action of SNP and IBA. However, Ca2+ chelators and Ca2+-channel inhibitors had no effect on SNP- and IBA-induced NO generation. It is concluded that cytosolic levels of Ca2+ may regulate SNP and IBA action through calmodulin-dependent mechanism.
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