Small ubiquitin-related modifier (SUMO) is a post-translational modification factor composed of about 100 amino acid residues. Most plant species express a family of SUMO isoforms. We found three novel homologs of rice (Oryza sativa L.) SUMO genes, OsSUMO4, OsSUMO5 and OsSUMO6, in addition to the known SUMO genes OsSUMO1-OsSUMO3. Phylogenetic tree analysis revealed that rice SUMO genes have diverged considerably during their evolution. All six of these SUMO genes complemented the phenotype of the SUMO-deficient pmt3Δ mutant of fission yeast. Among the amino acid sequences of rice SUMO proteins, consensus motifs (ΨKXE/D) of the SUMO acceptor site were found in OsSUMO3, OsSUMO4, OsSUMO5 and OsSUMO6. The heat shock protein HSF7 is known to be SUMOylated in Arabidopsis thaliana. SUMOylation using a bacterial expression system revealed that the rice HSF7 homolog was modified by the six rice SUMOs, and further suggested that OsSUMO1, OsSUMO3, OsSUMO4 and OsSUMO6 are involved in its multiple SUMOylation.

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a b s t r a c t Full-length cDNAs of three genes encoding glyceraldehyde-3-phosphate dehydrogenases (GPDs), PoGPD1, PoGPD2-1, and PoGPD2-2, and their corresponding genomic DNA were isolated from the basidiomycete mushroom Pleurotus ostreatus strain H1. The deduced amino acid sequences of PoGPD1, PoGPD2-1, and PoGPD2-2 had a high degree of similarity to known GPDs of other organisms, especially basidiomycetes. Similar to GPDs of other organisms, the three PoGPDs consist of the GPD NAD þ -binding domain, the GPD C-terminal catalytic domain, and conserved amino acid domains responsible for catalysis, cofactor binding, and substrate binding. Genomic sequence analysis revealed that PoGPD1, PoGPD2-1, and PoGPD2-2 contained seven, eight, and seven introns, respectively, with highly conserved positions. Comparison of the genomic sequences of PoGPD2-1 and PoGPD2-2 in the dikaryon of strain H1 and monokaryons of strain H1 revealed that PoGPD2-1 and PoGPD2-2 are different alleles of PoGPD2. Real-time quantitative reverse-transcription-PCR revealed that the expression patterns of PoGPD1 and PoGPD2 differed during fruit-body development. Specifically, transcript levels of PoGPD1 were high in the primordial stage, while transcript levels of PoGPD2 were high in the mycelial stage. Furthermore, levels of both transcripts were the highest in the base of mature fruit bodies.

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