Kiyosawa H, Hughes J E, Welker D L
Department of Biology, Utah State University, Logan 84322-5500.
Plasmid. 1994 Mar;31(2):121-30. doi: 10.1006/plas.1994.1013.
Dictyostelium mucoroides plasmids Dmp1 and Dmp2 are naturally occurring compatible members of the Dictyostelium Ddp1 plasmid family found in the same wild isolate strain. The nucleotide sequences of Dmp1 (5983 bp) and Dmp2 (6018 bp) are 74% identical and each carries open reading frames (ORFs) similar to the G1 and G5 ORFs of the Dictyostelium discoideum plasmid Ddp1. The predicted protein product of the Ddp1 G1 ORF is 49% similar to that of the Dmp1 G1-like ORF and 52% similar to that of the Dmp2 G1-like ORF. For the G5 and G5-like ORFs the corresponding values are 47 and 43%, respectively. The G1 and G5 ORFs of Ddp1 are transcribed during both vegetative growth and development of the asexual fruiting body. The G1-like ORF of Dmp2 is expressed in vegetative and developing cells, while that of Dmp1 appears to be expressed mostly in developing cells. The G5-like ORFs of Dmp1 and Dmp2 are expressed in both vegetative and developing cells. Dmp1 and Dmp2 differ from Ddp1 in (1) lacking homologs for the Ddp1 G2/G3/D4, G4/D5, D1/D3, and D2 ORFs; (2) containing multiple copies of a 173 bp direct repeat; and (3) having a different orientation of the G1 ORF relative to the G5 ORF. These findings suggest that the basic replicon unit of the Ddp1 plasmid family is composed of an origin of replication coupled to G1-like and G5-like genes. The additional ORFs and direct repeat elements in Ddp1, Dmp1, and Dmp2 may provide accessory functions beneficial to plasmid maintenance. Shuttle vectors based on Dmp1 or Dmp2 replicate in D. discoideum transformants.
盘基网柄菌黏液霉样质粒Dmp1和Dmp2是在同一野生分离菌株中发现的盘基网柄菌Ddp1质粒家族中天然存在的相容成员。Dmp1（5983 bp）和Dmp2（6018 bp）的核苷酸序列有74%的同一性，且各自携带与盘基网柄菌盘基网柄菌质粒Ddp1的G1和G5开放阅读框（ORF）相似的开放阅读框。Ddp1 G1 ORF的预测蛋白质产物与Dmp1 G1样ORF的预测蛋白质产物有49%的相似性，与Dmp2 G1样ORF的预测蛋白质产物有52%的相似性。对于G5和G5样ORF，相应的值分别为47%和43%。Ddp1的G1和G5 ORF在无性子实体的营养生长和发育过程中均被转录。Dmp2的G1样ORF在营养细胞和发育细胞中均有表达，而Dmp1的G1样ORF似乎主要在发育细胞中表达。Dmp1和Dmp2的G5样ORF在营养细胞和发育细胞中均有表达。Dmp1和Dmp2与Ddp1的不同之处在于：（1）缺乏Ddp1 G2/G3/D4、G4/D5、D1/D3和D2 ORF的同源物；（2）含有173 bp直接重复序列的多个拷贝；（3）G1 ORF相对于G5 ORF有不同的方向。这些发现表明，Ddp1质粒家族的基本复制子单元由与G1样和G5样基因相连的复制起点组成。Ddp1、Dmp1和Dmp2中的额外ORF和直接重复元件可能提供有利于质粒维持的辅助功能。基于Dmp1或Dmp2的穿梭载体在盘基网柄菌转化体中复制。
