PURIFICATION AND CHARACTERIZATION OF HISTONE H1 FROM MEIOTIC CELLS OFA MONOCOTYLEDONOUS PLANT, LILIUM-LONGIFLORUM

To identify molecules involved in regulating meiotic chromatin structu re, nuclear proteins from meiocytes of Lilium longiflorum were chromat ographed on hydroxylapatite and the bound and unbound proteins were ex amined. An abundant nuclear protein was purified from the unbound frac tion and by the following criteria was identified as a histone H1 mole cule. The protein is soluble in acidic (perchloric and sulfuric acid) solutions, and its amino acid composition and the sequence of its amin o terminus are similar to that of known histone H1s. An antiserum was produced against the protein to facilitate subsequent studies. Immunob lotting experiments demonstrated that histone H1 immunostaining declin es in the developmental interval spanning the diplotene to tetrads sta ges. Concommitant with this decline is the appearance of several lower molecular mass, cross-reacting proteins. Neither the identity nor rol es of these proteins is known. Immunoblotting experiments also demonst rate that, while the level of the protein is relatively constant in nu clei prepared from meiotic and vegetative cells, histone H1 is apparen tly enriched in total cellular extracts of meiotic cells compared with vegetative cells. This difference was found to be at least 16-fold. I conclude that in meiotic cells, histone H1 accounts for more of the t otal cellular protein than it does in vegetative cells. The difference in its relative abundance as a percent of the total cellular protein is probably in part due to differences in the ratio of nuclear to cyto plasmic volume in the different cell types, or the purging of sporophy tic proteins from the cytoplasm of the meiocytes, or both.