Canel C, Bailey-Serres J N, Roose M L
Department of Botany and Plant Sciences, University of California, Riverside 92521, USA.
Plant Mol Biol. 1996 Apr;31(1):143-7. doi: 10.1007/BF00020613.
Pummelo (Citrus maxima [Burm.] Merrill) cDNAs encoding mitochondrial citrate synthase (mCS) were cloned by reverse transcription of juice-sac poly(A)+ mRNA, followed by Taq Polymerase-mediated amplification. The nucleotide sequence of the citrus gene (cit1) is 77% conserved relative to plant mRNAs for mCS. The encoded polypeptide includes a mitochondrial targeting signal at its amino terminus; all 20 putative active-site residues of the citrus enzyme are conserved. Southern hybridization showed that citrus cit1 is a single-copy gene. A polymorphism associated with cit1 did not cosegregate with fruit acidity indicating that acitric, the gene causing the acidless phenotype of pummelo 2240, is not an allele of cit1 locus. Quantitative detection of cit1 mRNA showed that transcript levels are not developmentally regulated in juice sacs; no differences were observed between high- and low-acid genotypes.
通过对柚囊泡聚腺苷酸加尾mRNA进行反转录，随后进行Taq聚合酶介导的扩增，克隆得到了编码线粒体柠檬酸合酶（mCS）的柚（Citrus maxima [Burm.] Merrill）cDNA。相对于植物mCS的mRNA，柑橘基因（cit1）的核苷酸序列有77%的保守性。所编码的多肽在其氨基末端包含一个线粒体靶向信号；柑橘酶的所有20个假定活性位点残基都是保守的。Southern杂交表明柑橘cit1是一个单拷贝基因。与cit1相关的多态性与果实酸度不共分离，这表明导致柚2240无酸表型的acitric基因不是cit1位点的等位基因。cit1 mRNA的定量检测表明，转录水平在囊泡中不受发育调控；在高酸和低酸基因型之间未观察到差异。
