Nirunsuksiri W, Sengupta-Gopalan C
Molecular Biology Program/Dept. of Agronomy and Horticulture/Plant Genetic Engineering Labs, New Mexico State University, Las Cruces 88003.
Plant Mol Biol. 1990 Dec;15(6):835-49. doi: 10.1007/BF00039424.
A gene encoding for nodulin-16 (N-16) was isolated from a soybean genomic library. Nucleotide sequence analysis of the cDNA and the genomic clone of N-16 indicated that the coding region of this gene is 330 bp long and is interrupted by a single intron of 494 bp. The coding region of the N-16 gene shows a high degree of localized sequence similarity with the coding sequence of soybean nodulin-24 (N-24). Sequence similarity between the two genes is limited to the coding region of 90 bp in the first exon and the first 54 bp in the second exon of the N-16 gene which is repeated as the 2nd, 3rd, and 4th exons in the N-24 gene. The N-24 gene has been postulated to be a result of repeated duplication of an insertion element consisting of the 54 bp exon and the flanking intron sequences. In the absence of sequence similarity in the regions flanking the 54 bp sequence between the N-16 and N-24 genes, the N-16 gene does not appear to be the ancestral gene. Both N-16 and N-24 have a similar hydrophobic amino terminal end suggesting that N-16 like N-24 is targeted to the peribacteroid membrane. Southern analysis of soybean genomic DNA shows the presence of other related sequences to the N-16 gene, one of which is found to be closely linked to it. Analysis of the temporal accumulation of the N-16 transcripts during nodule development in effective and ineffective nodules suggests that N-16 and related genes might differ from leghemoglobin and some other late nodulin genes in their mechanism of regulation.
从大豆基因组文库中分离出了一个编码根瘤球蛋白-16（N-16）的基因。对N-16的cDNA和基因组克隆进行核苷酸序列分析表明，该基因的编码区长度为330 bp，被一个494 bp的单一内含子打断。N-16基因的编码区与大豆根瘤球蛋白-24（N-24）的编码序列表现出高度的局部序列相似性。两个基因之间的序列相似性仅限于N-16基因第一个外显子中90 bp的编码区以及第二个外显子中前54 bp，这部分序列在N-24基因中作为第二、第三和第四外显子重复出现。据推测，N-24基因是由一个由54 bp外显子和侧翼内含子序列组成的插入元件重复复制产生的。由于N-16和N-24基因中54 bp序列侧翼区域缺乏序列相似性，N-16基因似乎不是祖先基因。N-16和N-24都有一个相似的疏水氨基末端，这表明N-16和N-24一样，被靶向到类菌体周膜。对大豆基因组DNA的Southern分析表明存在与N-16基因相关的其他序列，其中一个被发现与它紧密连锁。对有效和无效根瘤中根瘤发育过程中N-16转录本的时间积累分析表明，N-16及相关基因在调控机制上可能与豆血红蛋白和其他一些晚期根瘤球蛋白基因不同。
