|Supena, Ence Darmo Jaya|
Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2006
Publication Date: 8/19/2006
Citation: Srinivasan, C., Liu, Z., Heidmann, I., Supena, E., Fukuoka, H., Joosen, R., Lambalk, J., Angenent, G., Scorza, R., Custers, J.B., Boutilier, K. 2006. Heterologous expression of the ap2/erf transcription factor baby boom alters the development and enhances the regeneration capacity of transgenic tobacco (nicotiana tabacum l.). Planta (2007) 225:341-351. Interpretive Summary: The role of plant genes in inducing adventitious shoot regeneration from in vitro cultured plant parts is not well understood. In order to induce adventitious shoot regeneration from in vitro cultured plants, a plant transcription factor gene BABY BOOM (BBM) was cloned from model plant species Arabidopsis thaliana and Brassica napa, and constitutively, expressed in transgenic tobacco (Nicotiana tabacum). The developmental alterations and regenerative competence of transgenic tobacco plants were evaluated. Constitutive expression of BBM genes with cauliflower mosaic virus 35S promoter altered leaf characters, changed flower color from pink to white, and caused reproductive sterility. However, expression of BBM gene by steroid-inducible post-translationally controlled BBM fusion protein induced somatic embryos and adventitious shoots, and roots from transgenic seedlings of tobacco.
Technical Abstract: Gain-of-function studies have shown that ectopic expression of the BABY BOOM (BBM) AP2/ERF domain transcription factor is sufficient to induce spontaneous somatic embryogenesis in Arabidopsis (Arabidopsis thaliana (L.) Heynh) and B. napus (Brassica napus L.). We examined the effect of ectopic BABY BOOM (BBM) expression on the development and regenerative capacity of tobacco (Nicotiana tabacum L.) through heterologous expression of Arabidopsis and B. napus BBM genes. 35S::BBM tobacco lines were obtained that exhibited a number of the vegetative and reproductive phenotypes previously observed in 35S::BBM Arabidopsis and B. napus transgenics, including callus formation, leaf rumpling, floral organ alterations and sterility. However, these tobacco transgenic lines did not produce spontaneous somatic embryogenesis or adventitious shoot formation. Highly regenerative BBM ectopic expression lines were subsequently obtained using a steroid-inducible, post-translationally controlled BBM fusion protein (35S::BBM:GR). While ectopic BBM expression in Arabidopsis and B. napus primarily induces spontaneous somatic embryo formation on seedlings, 35S::BBM:GR expression in tobacco induced ectopic shoot and root formation. Spontaneous somatic embryogenesis was not observed in the 35S::BBM:GR tobacco lines. Together, this data suggests that ectopic BBM expression in transgenic tobacco also induces cell proliferation and morphogenesis responses, but that major differences exist between Arabidopsis/B. napus and tobacco with respect to their developmental competence to respond to the BBM signalling molecule.