Studies on lateral root formation in rice: the effects of methyl jasmonate and cobalt chloride
Date Issued
2012
Date
2012
Author(s)
Hsu, Yun-Yen
Abstract
In this thesis, the role of nitric oxide (NO), heme oxygenase (HO) and Ca2+ in regulating methyl jasmonate (MJ)-induced lateral roots (LR) formation in rice cultivar TN1 (Oryza sativa L. cv. Taichung Native 1) was examined. Also included in this thesis is the possible mechanism of CoCl2-promoted LR formation in rice.
Application of MJ to rice seedlings promoted LR formation and NO production. Treatment with MJ and NO specific scavenger carboxy-2-phenyl-4, 4, 5, 5- tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) reduced MJ-induced LR formation and NO production. NO was detected by the specific fluorescence probe, 4-amino-5- ethylamino-2’, 7’-difluoroflorescein diacetate (DAF-FM DA). NR inhibitor, sodium tungstates (Tu), completely inhibited MJ-induced LR formation and NO fluorescence. However, nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) slightly reduced MJ-induced LR formation and NO generation, suggesting that NR activity is involved in MJ-increased NO production in rice roots. Moreover, the fluorescence of the longitudinal section of roots showed that NO production induced by MJ was localized in the LR primodia. It suggests that NO is a signal molecule involved in the regulation of MJ-induced LR formation.
MJ was able to increased rice seedlings HO activity. The time-course analyses of HO activity and LR formation clearly indicated that MJ-induced HO activity occurred before LR formation. Treatment with zinc protoporphyrinIX (ZnPPIX), an HO inhibitor, and hemoglobin (Hb), a CO scavenger, blocked MJ-induced LR formation and HO activity. Moreover, BV, another product of HO, also triggered LR development and HO activity. Pretreatment of Ca2+ chelators, channel blockers and camodulin antagonists inhibited MJ-promoted LR formation, but had no effect on MJ-induced HO activity.
Rice seedlings treated with CoCl2 also could promoted LR formation and HO activity. The time-course analyses of HO activity and LR formation clearly indicated that CoCl2-induced HO activity occurred before LR formation. ZnPPIX and Hb were able to reduced HO activity and the number of LR. CoCl2 (20 μM) had no effect on H2O2 production. Moreover, ascorbic acid (AsA) had no effect on CoCl2-induced HO activity and the LR number. It appears that reactive oxygen species (ROS) is not involved in the CoCl2-induced LR formation.
Subjects
calcium
cobalt chloride
heme oxygenase
lateral root
methyl jasmonate
nitric oxide
Oryza sativa
Type
thesis
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