Del Valle-Echevarria A R, Sanseverino W, Garcia-Mas J, Havey M J
Department of Horticulture, University of Wisconsin-Madison, 1575 Linden Drive, Madison, USA.
IRTA, Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, 08193, Barcelona, Spain.
Theor Appl Genet. 2016 Oct;129(10):1951-9. doi: 10.1007/s00122-016-2751-x. Epub 2016 Jul 16.
Pentatricopeptide repeat (PPR) 336 was identified as the candidate gene for Paternal Sorting of Mitochondria ( Psm ), a nuclear locus that affects the predominant mitochondria transmitted to progenies. Cucumber (Cucumis sativus L.) is a useful plant to study organellar-nuclear interactions because its organelles show differential transmission, maternal for chloroplasts and paternal for mitochondria. The mitochondrial DNA (mtDNA) of cucumber is relatively large due in part to accumulation of repetitive DNAs and recombination among these repetitive regions produces structurally polymorphic mtDNAs associated with paternally transmitted mosaic (MSC) phenotypes. The mitochondrial mutant MSC16 possesses an under-representation of ribosomal protein S7 (rps7), a key component of the small ribosomal subunit in the mitochondrion. A nuclear locus, Paternal Sorting of Mitochondria (Psm), affects the predominant mitochondria transmitted to progenies generated from crosses with MSC16 as the male parent. Using single nucleotide polymorphisms, Psm was mapped to a 170 kb region on chromosome 3 of cucumber and pentatricopeptide repeat (PPR) 336 was identified as the likely candidate gene. PPR336 stabilizes mitochondrial ribosomes in Arabidopsis thaliana and because MSC16 shows reduced transcription of rps7, the cucumber homolog of PPR336 (CsPPR336) as the candidate for Psm is consistent with a nuclear effect on ribosome assembly or stability in the mitochondrion. We used polymorphisms in CsPPR336 to genotype progenies segregating at Psm and recovered only one Psm -/- plant with the MSC phenotype, indicating that the combination of the Psm- allele with mitochondria from MSC16 is almost always lethal. This research illustrates the usefulness of the MSC mutants of cucumber to reveal and study unique interactions between the mitochondrion and nucleus.
五肽重复序列（PPR）336被鉴定为线粒体父系分选（Psm）的候选基因，Psm是一个影响传递给后代的主要线粒体的核基因座。黄瓜（Cucumis sativus L.）是研究细胞器-核相互作用的有用植物，因为其细胞器表现出不同的遗传方式，叶绿体为母系遗传，线粒体为父系遗传。黄瓜的线粒体DNA（mtDNA）相对较大，部分原因是重复DNA的积累，这些重复区域之间的重组产生了与父系传递的镶嵌（MSC）表型相关的结构多态性mtDNA。线粒体突变体MSC16的核糖体蛋白S7（rps7）表达不足，rps7是线粒体小核糖体亚基的关键组成部分。一个核基因座，线粒体父系分选（Psm），影响与以MSC16为父本杂交产生的后代中传递的主要线粒体。利用单核苷酸多态性，Psm被定位到黄瓜3号染色体上一个170 kb的区域，五肽重复序列（PPR）336被鉴定为可能的候选基因。PPR336在拟南芥中稳定线粒体核糖体，由于MSC16显示rps7的转录减少，黄瓜中PPR336的同源物（CsPPR336）作为Psm的候选基因与核基因对线粒体核糖体组装或稳定性的影响一致。我们利用CsPPR336中的多态性对在Psm处分离的后代进行基因分型，仅获得了一株具有MSC表型的Psm-/-植株，这表明Psm等位基因与来自MSC16的线粒体的组合几乎总是致死的。这项研究说明了黄瓜的MSC突变体在揭示和研究线粒体与细胞核之间独特相互作用方面的有用性。
