Adams K L, Rosenblueth M, Qiu Y L, Palmer J D
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Genetics. 2001 Jul;158(3):1289-300. doi: 10.1093/genetics/158.3.1289.
Unlike in animals, the functional transfer of mitochondrial genes to the nucleus is an ongoing process in plants. All but one of the previously reported transfers in angiosperms involve ribosomal protein genes. Here we report frequent transfer of two respiratory genes, sdh3 and sdh4 (encoding subunits 3 and 4 of succinate dehydrogenase), and we also show that these genes are present and expressed in the mitochondria of diverse angiosperms. Southern hybridization surveys reveal that sdh3 and sdh4 have been lost from the mitochondrion about 40 and 19 times, respectively, among the 280 angiosperm genera examined. Transferred, functional copies of sdh3 and sdh4 were characterized from the nucleus in four and three angiosperm families, respectively. The mitochondrial targeting presequences of two sdh3 genes are derived from preexisting genes for anciently transferred mitochondrial proteins. On the basis of the unique presequences of the nuclear genes and the recent mitochondrial gene losses, we infer that each of the seven nuclear sdh3 and sdh4 genes was derived from a separate transfer to the nucleus. These results strengthen the hypothesis that angiosperms are experiencing a recent evolutionary surge of mitochondrial gene transfer to the nucleus and reveal that this surge includes certain respiratory genes in addition to ribosomal protein genes.
与动物不同，线粒体基因向细胞核的功能转移在植物中是一个持续进行的过程。在被子植物中，除了先前报道的一次转移外，其他所有转移都涉及核糖体蛋白基因。在此，我们报告了两个呼吸基因sdh3和sdh4（分别编码琥珀酸脱氢酶的亚基3和亚基4）的频繁转移，并且我们还表明这些基因存在于多种被子植物的线粒体中并在其中表达。Southern杂交调查显示，在所检测的280个被子植物属中，sdh3和sdh4分别从线粒体中丢失了约40次和19次。分别在四个和三个被子植物科中从细胞核中鉴定出了转移的、具有功能的sdh3和sdh4拷贝。两个sdh3基因的线粒体靶向前导序列源自古老转移的线粒体蛋白的现有基因。基于核基因独特的前导序列和最近线粒体基因的丢失情况，我们推断七个核sdh3和sdh4基因中的每一个都源自一次独立的向细胞核的转移。这些结果强化了这样一种假说，即被子植物正在经历线粒体基因向细胞核的近期进化激增，并且表明这种激增除了核糖体蛋白基因外还包括某些呼吸基因。
