The distribution of a spliceosome protein in cereal (Triticeae) interphase nuclei from cells with different metabolic activities and through the cell cycle.

A monoclonal antibody (mAb) KSm2 and three human Sm sera, which detect the 'D' polypeptide in mammals and is associated with the U1, U2, U4/U6, U5, U7, U9-U12 small nuclear RNAs, have been used in Western blotting to show that the antigen is conserved in wheat (Triticum aestivum cv. Beaver). Immunocytochemistry to wheat and a barley (Hordeum vulgare) suspension culture using the mAb KSm2 has shown that the 'D' polypeptide occurs in interphase nuclei as speckles and foci outside the nucleoli and as tracks. Nucleoli usually had at least one focus at their periphery. Immunocytochemistry at the electron microscope level of resolution has shown that the signal occurs between chromatin axes and predominantly in the outer domain of the nucleus. Analysis of the barley suspension culture demonstrated that there was a significant increase in antigen through G1, S to G2. In the wheat meristematic cells at prophase only the foci remained, and at metaphase the distribution of foci was asymmetrical with foci occurring either at one pole or on the metaphase plate. At telophase the foci appeared to decrease in size and were incorporated non-uniformly into the daughter nuclei because of their asymmetric distribution at metaphase. When wheat was grown at a range of temperatures, the root tip meristematic nuclei showed a number of different organization patterns. The average number of nucleoli increased and their size decreased. At the same time there was an increase in the average total area of foci as temperature increased from 4 degrees, 10 degrees, 25 degrees, 34 degrees, to 37 degrees C. Thus the 'D' polypeptide distribution changes with metabolic activity and through the cell cycle.