The differentiation of gametes involves dramatic changes to chromatin, affecting 
transcription, meiosis, and cell morphology. Sporulation in Saccharomyces 
cerevisiae shares many chromatin features with spermatogenesis, including a 
10-fold compaction of the nucleus. To identify new proteins involved in spore 
nuclear organization, we purified chromatin from mature spores and discovered a 
significant enrichment of the linker histone (Hho1). The function of Hho1 has 
proven to be elusive during vegetative growth, but here we demonstrate its 
requirement for efficient sporulation and full compaction of the spore genome. 
Hho1 chromatin immunoprecipitation followed by sequencing (ChIP-seq) revealed 
increased genome-wide binding in mature spores and provides novel in vivo 
evidence of the linker histone binding to nucleosomal linker DNA. We also link 
Hho1 function to the transcription factor Ume6, the master repressor of early 
meiotic genes. Hho1 and Ume6 are depleted during meiosis, and analysis of 
published ChIP-chip data obtained during vegetative growth reveals a high 
binding correlation of both proteins at promoters of early meiotic genes. 
Moreover, Ume6 promotes binding of Hho1 to meiotic gene promoters. Thus, Hho1 
may play a dual role during sporulation: Hho1 and Ume6 depletion facilitates the 
onset of meiosis via activation of Ume6-repressed early meiotic genes, whereas 
Hho1 enrichment in mature spores contributes to spore genome compaction.