A frameshift in the coding region of a novel tomato class I basic chitinase gene makes it a pseudogene with a functional wound-responsive promoter

摘要

A putative class I basic chitinase gene, assigned as psi BCH, was cloned from a tomato breeding line NC 24E. The gene contains a coding region with two introns. The predicted psi BCH open reading frame (ORF) is 971 bp and exhibits 81-88% identity at the nucleotide level with known class I basic chitinase genes from the Solanaceae family. However, the presence of a stop codon caused by a frameshift in the ORF of psi BCH makes it unusual among the other class I plant basic chitinases. This stop codon might be involved in the lower accumulation of fully spliced psi BCH RNA caused by nonsense-mediated decay (NMD), which is an RNA surveillance system universally found in eukaryotes. Sequence analysis of the 1883-bp 5'-flanking region, of the psi BCH gene revealed the presence of potential wound-response promoter elements. To study the transcriptional regulation of the psi BCH gene, its 5'-flanking region containing the putative promoter was fused to the gus reporter gene and introduced into the tobacco genome via Agrobacterium tumefaciens-mediated transformation. Transgenic plants were functionally assayed for beta-glucuronidase activity. The psi BCH promoter drives the reporter gene expression in response to wounding stimuli. psi BCH promoter-GUS analysis indicates that wound-response of the tobacco transgene was rapid and localized in the wounded area following mechanical wounding. Therefore, our results suggest that the psi BCH promoter can provide targeted expression of genes, such as protease inhibitors in response to pest attack. (c) 2006 Elsevier B.V. All rights reserved.