Translation in a wheat germ cell-free system of RNA from mitochondria of the normal and Texas male-sterile cytoplasms of maize (Zea mays L.)

Abstract

RNA isolated from etiolated seedling shoot mitochondria of maize (Zea mays L.) with normal (N) or Texas male-sterile (T) cytoplasm stimulated the incorporation of [35S]-methionine into protein when added to a cell-free protein-synthesizing system from wheat germ. Discrete polypeptides with molecular masses of up to approximately 67 kDa were synthesized, and the pattern of bands was distinct from that obtained with total RNA. Products of translation of T-urf13 RNA were identified by immunoprecipitation, and of atpA, coxI, and coxII RNA by hybrid arrest of translation by the cloned gene. Several polypeptides were differentially synthesized from N and T mitochondrial RNA; these differences were more extensive than those found when isolated, intact, N and T mitochondria are allowed to synthesize proteins.

Regulation of gene expression in plant mitochondria

“…This difficulty seems to be a general feature of organelle protein synthesis since in animals and fungi it has also been impossible so far to obtain competent in vitro translation. A total wheat cell-free system, however, has been found to be capable of recognizing plant mitochondrial mRNAs and to synthesize at least some of the encoded mitochondrial polypeptides with apparently correct protein sizes [25]. However, extensive aberrant protein synthesis also occurs as expected in such heterologous experiments.…”