Efficient synthesis of rabbit globin in a cell-free system from wheat embryo.

A cell-free preparation isolated from wheat embryos has been used successfully for the analysis of protein chain initiation with natural mRNA’s primarily of plant viral origin [l-4]. A tacit assumption in these studies has been that the ribosome-mRNA attachment reaction with the viral RNA’s was equivalent to the reaction with cellular mRNA’s. In the present communication we test this assumption by inquiring as to whether rabbit globin mRNA [5] can be translated in the wheat embryo cell-free system. This experiment has the additional significance of providing a more rigorous examination of the question as to whether ribosome systems discriminate between mRNA’s. It has been shown in other studies [6-131 that globin mRNA’s can be translated in vitro in systems from mammalian species that normally do not encounter this mRNA. Wheat embryos are phylogenetically quite distant from mammals. As such, an efficient synthesis of rabbit globin in the wheat system would considerably extend the concept of the lack of ribosome and initiation factor specificity. We report herein that this is indeed the case. Rabbit globin mRNA catalyzes the incorporation of leucine in the wheat embryo cell-free system at a rate equivalent to that obtained with the most active heterologous mammalian systems. The products of the reaction are examined by a number of criteria and shown to be exclusively the (Y and /3 chains of rabbit globin. 2. Materials and methods