Wound-induced expression of the FAD7 gene is mediated by different regulatory domains of its promoter in leaves/stems and roots.

Abstract

The FAD7 gene is expressed preferentially in the chlorophyllous tissues of unwounded plants. Wounding activates the expression of the FAD7 gene not only in chlorophyllous tissues, but also in nonchlorophyllous tissues of stems and roots. Our previous study suggested that wound-responsive transcriptional activation by the FAD7 promoter in leaves/stems and roots is brought about by a jasmonic acid (JA)-independent and JA-dependent signaling pathway, respectively. In this paper, we show that a specific region (from -259 to -198) in the FAD7 promoter is required for wound-activated expression of this gene in leaves and stems, while another region (from -521 to -363) is necessary not only for wound-activated but also for JA-responsive expression of this gene in roots. Thus, different regulatory regions of the FAD7 promoter mediate distinct wound-induced expression of this gene in leaves/stems and roots. Gel mobility shift assays revealed the wound-inducible DNA-binding activity to the -242/-223 region in both stem and leaf nuclear extracts. In fact, deletion of this region abolished wound response of the FAD7 promoter, suggesting the in vivo role of this site. Furthermore, we detected root nuclear factors interacting with the region from -433 to -363 of this promoter. Wounding and methyl jasmonate treatments induced differently these DNA-binding activities. These results suggest that different regulatory mechanisms mediate the wound-induced expression of the FAD7 gene in aerial and subterranean organs.