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Abstract Detail


Mechanisms of Gene Regulation

El Sherif, Nahla [1], Goldsbrough, Peter [2].

Salicylic acid is required for safener-induced expression of glutathione S-transferases in Arabidopsis .

Herbicide safeners are chemical compounds that enhance the selectivity of herbicides in cereal crops and act primarily by inducing herbicide detoxifying enzymes including glutathione S-transferases (GSTs). Plant GSTs have well described roles in the detoxification and tolerance of herbicides in crops. However, individual GSTs are expressed in response to many cues, including various forms of biotic and abiotic stress, suggesting that GSTs also have diverse functions in normal metabolism. In Arabidopsis, safeners induce the organ-specific RNA expression of AtGSTU19 and AtGSTF2, two genes from different classes of the GST superfamily. Promoter deletion analysis showed that an as-1 element located approximately150 bp upstream of the transcription start site in AtGSTU19 is required for safener-induced expression of this gene. Specific mutations within the as-1 element also abolished the capacity of the AtGSTU19 promoter to respond to safeners. Salicylic acid (SA) is known to regulate the expression of many genes that contain as-1 elements. RNA expression of AtGSTU19 was induced by treatment of seedlings with SA, while the safeners benoxacor and fenclorim were unable to induce AtGSTU19 in SA-deficient NahG plants. These results support the hypothesis that safeners function through a SA signaling pathway in Arabidopsis. However, the sid2 mutant, which is deficient in SA biosynthesis via the isochorismate synthase pathway, showed normal induction of AtGSTU19 by benoxacor. These results indicate the involvement of an alternative SA biosynthesis pathway, from phenylalanine and benzoic acid, in activating the expression of AtGSTU19 and other xenobiotic detoxification genes in response to safeners.


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1 - Purdue University, Horticulture and Landscape Architecture, 625 Agricultural Mall Drive, West Lafayette, IN, 47907-2010, USA
2 - Purdue University, Department of Botany and Plant Pathology, Lilly Hall of Life Sciences, 915 W State Street, West Lafayette, Indiana, 47907, USA

Keywords:
GST
safeners
salicylic acid
phenyl alanine
glutathione S-transferases.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P36005
Abstract ID:282


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