Goldschmidt-Clermont M, Girard-Bascou J, Choquet Y, Rochaix J D
Department of Plant Biology, University of Geneva, Switzerland.
Mol Gen Genet. 1990 Sep;223(3):417-25. doi: 10.1007/BF00264448.
In Chlamydomonas reinhardtii the three exons of the psaA gene are widely scattered on the chloroplast genome: exons 1 and 2 are in opposite orientations and distant from each other and from exon 3. The mature mRNA, encoding a core polypeptide of photosystem I, is thus probably assembled from separate precursors by splicing in trans. We have isolated and characterized a set of mutants that are deficient in the maturation of psaA mRNA. The mutants belong to 14 nuclear complementation groups and one chloroplast locus that are required for the assembly of psaA mRNA. The chloroplast locus, tscA, is remote from any of the exons and must encode a factor required in trans. The mutants all show one of only three phenotypes that correspond to defects in one or other or both of the joining reactions. These phenotypes, and those of double mutants, are consistent with the existence of two alternative splicing pathways.
在莱茵衣藻中，psaA基因的三个外显子广泛散布于叶绿体基因组上：外显子1和外显子2方向相反，彼此相距甚远，且与外显子3也相距较远。因此，编码光系统I核心多肽的成熟mRNA可能是通过反式剪接由单独的前体组装而成。我们已分离并鉴定出一组在psaA mRNA成熟过程中存在缺陷的突变体。这些突变体属于14个核互补群和一个叶绿体基因座，它们是组装psaA mRNA所必需的。叶绿体基因座tscA远离任何一个外显子，必定编码一种反式作用所需的因子。这些突变体均表现出仅三种表型中的一种，这三种表型分别对应于一种或另一种或两种连接反应中的缺陷。这些表型以及双突变体的表型与两种替代剪接途径的存在相一致。
