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Transcriptional Down-Regulation by Abscisic Acid of Pathogenesis-Related β-1,3-Glucanase Genes in Tobacco Cell Cultures

Enea Rezzonico, Nathalie Flury, Frederick Meins, Jr. and Roland Beffa
Plant Physiology
Vol. 117, No. 2 (Jun., 1998), pp. 585-592
Stable URL: http://www.jstor.org/stable/4278311
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Transcriptional Down-Regulation by Abscisic Acid of Pathogenesis-Related β-1,3-Glucanase Genes in Tobacco Cell Cultures
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Abstract

Class I isoforms of β-1,3-glucanases (βGLU I) and chitinases (CHN I) are antifungal, vacuolar proteins implicated in plant defense. Tobacco (Nicotiana tabacum L.) βGLU I and CHN I usually exhibit tightly coordinated developmental, hormonal, and pathogenesis-related regulation. Both enzymes are induced in cultured cells and tissues of cultivar Havana 425 tobacco by ethylene and are down-regulated by combinations of the growth hormones auxin and cytokinin. We report a novel pattern of βGLU I and CHN I regulation in cultivar Havana 425 tobacco pith-cell suspensions and cultured leaf explants. Abscisic acid (ABA) at a concentration of 10 μM markedly inhibited the induction of βGLU I but not of CHN I. RNA-blot hybridization and immunoblot analysis showed that only class I isoforms of βGLU and CHN are induced in cell culture and that ABA inhibits steady-state βGLU I mRNA accumulation. Comparable inhibition of β-glucuronidase expression by ABA was observed for cells transformed with a tobacco βGLU I gene promoter/β-glucuronidase reporter gene fusion. Taken together, the results strongly suggest that ABA down-regulates transcription of βGLU I genes. This raises the possibility that some of the ABA effects on plant-defense responses might involve βGLU I.

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