DNA, histone H1 and meiotin-1 immunostaining patterns along whole-mount preparations of Lilium longiflorum pachytene chromosomes.

Meiotin-1 is a chromatin protein found in lily microsporocytes preceding and during meiosis. It reaches peak levels in the leptotene-pachytene interval. Here we report the pattern of immunostaining of meiotin-1 along pachytene chromosomes prepared using a whole-mount, synaptonemal complex spreading technique. Meiotin-1 immunostaining, like immunostaining for histone H1 and DNA, is found all along the lengths of the chromosomes. Unlike histone H1 and DNA immunostaining, there are several patches of particularly intense meiotin-1 immunostaining. The sites of intense staining may be clustered in the in vivo nucleus. The distribution of meiotin-1 along the width of the chromosomes was examined and compared with the pattern of histone H1 and DNA immunostaining. All three were distributed across the width of the chromosome, and did not appear to be preferentially associated with the synaptonemal complex. There was a slight suggestion that histone H1 and meiotin-1 may be located preferentially away from the synaptonemal complex. The temporal and spatial distribution of meiotin-1 in microsporocytes and tapetal cells, and the chemical and physical properties of meiotin-1, are discussed in the context of our hypothesis that meiotin-1 is a protein that functions to limit the degree of chromosome condensation during prophase I of meiosis.