Developmental expression of polyubiquitin genes and distribution of ubiquitinated proteins in generative and sperm cells

Polyubiquitin-encoding cDNA clones were isolated from the generative cells of lily (Lilium longiflorum) and the sperm cells of Plumbago zeylanica. The described genes encode identical amino acid sequences, with no homology outside the coding regions. This gene participates in ubiquitination of proteins, presumably enhancing protein turnover in the germline during male reproductive differentiation. In this paper we show that the gene encoding polyubiquitin is highly up-regulated in both Lilium generative cells and one of the Plumbago sperm cell types in particular.