A Tobacco Knotted-1 Related Homeobox Gene for Investigating In Vitro Shoot Formation

Abstract

Knotted homeobox genes have been previously identified in a number of monocot and dicot species and the similarity in their amino acid sequences suggests a fundamental role in the process of shoot meristem formation. Knotted type homeodomains can be divided into two classes. Class 1 genes share high sequence homol. within the homeodomain and are expressed primarily in meristem enriched regions such as the shoot and floral primordia and also in the unexpanded stem but not in the leaves or roots. Class 2 genes on the other hand are expressed in varying levels in all tissues. The discovery of these genes has stimulated the conjecture that a knotted gene may be used as a functional early detection marker for in vitro studies of shoot formation. To address this, a PCR-based cloning approach was used to isolate a 389 bp fragment of a knotted like gene from Nicotiana tabacum var. zz100 (TobH1). The expression of this gene during tobacco leaf disk organogenesis is currently being examined Based on the conservation of sequence identity and expression pattern, TobH1 is most likely part of the NTH15 knotted gene. This fragment is being used to clarify the above conjecture.