Present address: Department of Biology, California State University, Fresno, California 93740, USA.
The helicase domain of the TMV replicase proteins induces the N-mediated defence response in tobacco
Article first published online: 5 JAN 2002
The Plant Journal
Volume 18, Issue 1, pages 67–75, April 1999
How to Cite
Les Erickson, F., Holzberg, S., Calderon-Urrea, A., Handley, V., Axtell, M., Corr, C. and Baker, B. (1999), The helicase domain of the TMV replicase proteins induces the N-mediated defence response in tobacco . The Plant Journal, 18: 67–75. doi: 10.1046/j.1365-313X.1999.00426.x
- Issue published online: 5 JAN 2002
- Article first published online: 5 JAN 2002
- tpj0426Received 30 November 1998; revised 4 February 1999; accepted 8 February 1999.
Tobacco mosaic virus (TMV) induces the hypersensitive response (HR) in tobacco plants containing the N gene. This defence response is characterized by cell death at the site of virus infection and inhibition of viral replication and movement. A previous study indicated that a portion of the TMV replicase containing a putative helicase domain is involved in HR induction. Here, this observation is confirmed and extended by showing that non-viral expression of a 50 kDa TMV helicase fragment (p50) is sufficient to induce the N-mediated HR in tobacco. Like the HR elicited by TMV infection, transgenic expression of p50 induces a temperature-sensitive defence response. We demonstrate that recombinant p50 protein has ATPase activity, as suggested by the presence of conserved sequence motifs found in ATPase/helicase enzymes. A point mutation that alters one of these motifs abolishes ATPase activity in vitro but does not affect HR induction. These results suggest that features of the TMV helicase domain, independent of its enzymatic activity, are recognized by N-containing tobacco to induce TMV resistance.