Transformation of Brassica juncea by Agrobacterium tumefaciens harbouring plasmid pTiT37 and its 'rooty' mutant pTiT37.14a/a

Abstract

Indian mustard (Brassica juncea Linn., Czern and Coss) plants were inoculated withAgrobacterium tumefaciens strain A208 harbouring either plasmid pTiT37 or pTiT37.14a/a. The latter carries an insertion at the 'rooty' locus (gene 4 orcyt) of the T-DNA governing cytokinin biosynthesis. The tumours induced by pTiT37.14a/a were small and formed many roots. Forin vitro culture, these transformed cells required supplementation of the basal medium with IAA and kinetin in the initial stages though after six sub-cultures they were also hormone autotrophic. In vitro cultures showed profuse rooting like the inplanta tumours. Unlike transformed tobacco and carrot cells, Brassica juncea cells transformed by pTiT37.14a/a could not be induced to differentiate into shoots. In contrast, the cells transformed by the wild type pTiT37 were hormone autotrophic and occasionally differentiated into shoots but could not be induced to produce roots. These results demonstrate how a single gene mutation affecting cytokinin biosynthesis can alter the inplanta as well as thein vitro response of a transformed cell of the same genotype.