Ethylene production by shoot-forming and unorganized crown-gall tumor tissues of Nicotiana and Lycopersicon cultured in vitro

Abstract

We have studied ethylene biosynthesis in cloned crown-gall cell lines of Nicotiana tabacum L., N. glutinosa L., and Lycopersicon esculentum (L.) Mill. transformed by the A6 strain of Agrobacterium tumefaciens (Smith and Townsend) Conn. or a tms (shooty) mutant strain, A66. Both the synthesis of the ethylene precursor 1-aminocyclo-propane-1-carboxylic acid (ACC) and the conversion of ACC to ethylene were affected by crown-gall transformation. All A6-transformed cell lines contained about 50 times more ACC than the A66-transformed cell lines, indicating that the tms genes stimulate ACC synthesis. On the other hand, A6-transformed N. tabacum and L. esculentum cell lines showed a very low capacity to convert ACC to ethylene when compared with A66-transformed cells of the same species. These differences in ACC-dependent ethylene formation were stable and could not be modified by supplying auxin to the culture medium. In contrast, both the A6- and A66-transformed N. glutinosa cell lines showed a low capacity for ACC-dependent ethylene production. Thus, the low-ethylene-forming phenotype did not seem to be under direct control of the tms genes and appeared to be part of the host response to crown-gall transformation. All cell lines exhibiting the low-ethylene-forming phenotype grew as unorganized tissues in culture, whereas cell lines showing a high capacity to convert ACC to ethylene formed shoots. Thus, ACC-dependent ethylene formation may be useful for studying host factors important in determining tumor phenotype.