Effect of seed-specific expression of the ipt Gene on Nicotiana tabacum L. seed composition

Author： Daskalova Sasha McCormac Alex Scott Nigel Onckelen Harry Elliott Malcolm

ISSN： 0167-6903

Source： Plant Growth Regulation, Vol.51, Iss.3, 2007-03, pp. : 217-229

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Abstract

A transgenic approach to manipulation of endosperm development has been investigated. Nicotiana tabacum cv. Xanthi, an endosperm-containing dicotyledon, has been used as a model plant and the 2.6 kb wheat high molecular weight (HMW) glutenin subunit 12 promoter has been used fused either to the gus reporter gene (HMWgus construct)—to study promoter characteristics—or to the Agrobacterium ipt gene—to study the effect of cytokinin (CK) over-expression on assimilate accumulation in the seed. In transgenic tobacco the promoter:gus fusion showed that HMW is an endosperm-specific promoter with maximum expression 20 days after anthesis (DAA), corresponding to the mid to late stages of seed development. Transgenic plants containing the HMWipt construct showed no morphological abnormalities but they had an average increase in seed weight and total ethanol-insoluble carbohydrates and protein content of 8.1%, 7.0% and 8.3%, respectively. SDS PAGE analysis demonstrated that the effect on protein accumulation was non-specific. The highest values of the parameters analysed correlated with moderate increases in the levels of biologically active CKs. These results suggest that ectopic expression of small amounts of CKs can be used to increase storage assimilate accumulation without a detrimental effect on development.