TITLE Phosphinothricin tolerance in rice (Oryza sativa L.) seedlings is associated with elevated abscisic acid in the leaves
AUTHOR Yi Ting Hsu
Department of Agronomy, National Taiwan University, Taipei, Taiwan, Republic of China
Ching Huei Kao*
Department of Agronomy, National Taiwan University, Taipei, Taiwan, Republic of China
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ABSTRACT Phosphinothricin (PPT, known as glufosinate) is a nonselective herbicide that is a potent inhibitor of glutamine synthetase (GS). PPT-tolerant and PPT-sensitive rice cultivars were used to study the role of abscisic acid (ABA) in PPT tolerance. ABA content was determined by enzyme-linked immunosorbent assay. PPT toxicity was evaluated by the decrease in chlorophyll and protein contents in the leaves. On treatment with PPT, ABA content significantly increased in the leaves of the PPT-tolerant cultivars (cv. Tainung 67, TNG67) but not in the PPT-sensitive cultivar (cv. Taichung Native 1, TN1). The reduction of transpiration rate of TN1 seedlings caused by PPT was less than that of TNG67. Pretreatment with ABA enhanced PPT tolerance and reduced PPT-induced NH4+ accumulation in leaves of TN1. Exogenous application of the ABA biosynthesis inhibitor, fluridone, decreased PPT tolerance and increased NH4+ content in the leaves of TNG 67. Fluridone effect on PPT toxicity of TNG67 seedlings was reversed by the application of ABA. Evidence is presented to show that PPT-induced NH4+ accumulation, rather than depletion of glutamine, is the mechanism that regulates PPT-induced toxicity in TN1 leaves. In conclusion, the increase in endogenous ABA content in the leaves is closely related to PPT tolerance of rice seedlings.
KEYWORD Abscisic acid; Ammonium ion toxicity; Glutamine synthetase; Phosphinothricin tolerance; Rice;
ARTICLE INFO Botanical Bulletin of Academia Sinica, Volume 45 Number 1 January 2004, page 41-48, 8 pages
PUBLISHER Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China