DeRocher E J, Quigley F, Mache R, Bohnert H J
Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721.
Mol Gen Genet. 1993 Jun;239(3):450-62. doi: 10.1007/BF00276944.
The nucleotide sequences of the entire gene family, comprising six genes, that encodes the Rubisco small subunit (rbcS) multigene family in Mesembryanthemum crystallinum (common ice plant), were determined. Five of the genes are arranged in a tandem array spanning 20 kb, while the sixth gene is not closely linked to this array. The mature small subunit coding regions are highly conserved and encode four distinct polypeptides of equal lengths with up to five amino acid differences distinguishing individual genes. The transit peptide coding regions are more divergent in both amino acid sequence and length, encoding five distinct peptide sequences that range from 55 to 61 amino acids in length. Each of the genes has two introns located at conserved sites within the mature peptide-coding regions. The first introns are diverse in sequence and length ranging from 122 bp to 1092 bp. Five of the six second introns are highly conserved in sequence and length. Two genes, rbcS-4 and rbcS-5, are identical at the nucleotide level starting from 121 bp upstream of the ATG initiation codon to 9 bp downstream of the stop codon including the sequences of both introns, indicating recent gene duplication and/or gene conversion. Functionally important regulatory elements identified in rbcS promoters of other species are absent from the upstream regions of all but one of the ice plant rbcS genes. Relative expression levels were determined for the rbcS genes and indicate that they are differentially expressed in leaves.
测定了冰叶日中花（普通冰草）中编码核酮糖-1,5-二磷酸羧化酶小亚基（rbcS）多基因家族的整个基因家族（由六个基因组成）的核苷酸序列。其中五个基因以串联排列的方式分布在20 kb的区域内，而第六个基因与该阵列没有紧密相连。成熟小亚基编码区高度保守，编码四种长度相等的不同多肽，个别基因之间最多有五个氨基酸差异。转运肽编码区在氨基酸序列和长度上差异更大，编码五种不同的肽序列，长度从55到61个氨基酸不等。每个基因在成熟肽编码区内的保守位点有两个内含子。第一个内含子在序列和长度上各不相同，从122 bp到1092 bp不等。六个第二个内含子中的五个在序列和长度上高度保守。两个基因rbcS-4和rbcS-5，从ATG起始密码子上游121 bp到终止密码子下游9 bp（包括两个内含子的序列）在核苷酸水平上是相同的，表明是最近的基因复制和/或基因转换。除了一个冰叶日中花rbcS基因外，其他所有基因的上游区域都没有在其他物种的rbcS启动子中鉴定出的功能重要的调控元件。测定了rbcS基因的相对表达水平，结果表明它们在叶片中差异表达。
