Studies on the Formation of Lateral Roots and Root Hairs in Rice
Date Issued
2011
Date
2011
Author(s)
Chen, Yi-Hsuan
Abstract
In this thesis, rice (Oryza sativa L. cv. Taichung Native 1, TN1, an Indica type) seedlings were used to investigate the involvement of Ca2+ and heme oxygenase (HO) in auxin- and nitric oxide (NO)-induced formation of lateral roots (LRs) and root hairs (RHs) and the effect of apocynin on LR formation.
Application of sodium nitroprusside (SNP; a NO donor), indole-3-butyric acid (IBA; a naturally occurring auxin), or hemin (Hm; a HO inducer) to rice seedlings induced the formation of LRs and RHs. LR and RH formation and NO production induced by SNP and IBA were prevented by the specific NO scavenger 2-(4-carboxyphenyl)-4,4,5,5- tetramethyl-imidazoline-1-oxyl-3-oxide (cPTIO). Hm had no effect on NO production. Hm-induced formation of LRs and RHs could not be blocked by cPTIO. Nitrate reductase (NR) inhibitor sodium tungstate completely inhibited IBA-induced LR and RH formations and NO production. Clearly the effect of IBA is attributed by NO released, and the NO generation in response to IBA might mainly involve NR activity. The effects of Ca2+ chelators, Ca2+-channel inhibitors, and calmodulin antagonists 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 Ca2+ is involved in SNP- and IBA-induced LR and RH formations, and is acting downstream of NO and IBA.
Treatment of rice seedlings with SNP, IBA, and Hm resulted in an enhancement of HO activity. Zn protoporphyrin IX (ZnPPIX; a HO inhibitor) and hemoglobin (Hb; a CO/NO scavenger) reduced the LR and RH formation and the enhancement of HO activity induced by SNP, IBA, and Hm. The product of HO catalyzed reaction, biliverdin IXα (BV), was also able to induce LR and RH formation and enhance HO activity. These data suggested that HO is involved in SNP-, IBA- and Hm-induced LR and RH formation.
Apocynin was able to induce LR formation and the generation of H2O2, which could be blocked by diphenylene iodonium (a NADPH oxidase inhibitor). These results indicate that the apocynin-induced LR formation is related to H2O2.
Subjects
auxin
nitric oxide
lateral root
root hair
rice
calcium
Type
thesis
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