Li Qing, Fang Chao, Duan Zongbiao, Liu Yucheng, Qin Hao, Zhang Jixiang, Sun Peng, Li Wenbin, Wang Guodong, Tian Zhixi
State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
University of Chinese Academy of Sciences, Beijing, 100039, China.
Plant J. 2016 Nov;88(4):584-596. doi: 10.1111/tpj.13282. Epub 2016 Sep 17.
Polyploidy is prevalent in nature. As the fate of duplicated genes becomes more complicated when the encoded proteins function as oligomers, functional investigations into duplicated oligomer-encoding genes in polyploid genomes will facilitate our understanding of how traits are expressed. In this study, we identified GmCHLI1, a gene encoding the I subunit of magnesium (Mg)-chelatase, which functions in hexamers as responsible for the semi-dominant etiolation phenotype in soybean. Four GmCHLI copies derived from two polyploidy events were identified in the soybean genome. Further investigation with regard to expression patterns indicated that these four copies have diverged into two pairs; mutation in the other copy of the pair that includes GmCHLI1 also resulted in a chlorophyll-deficient phenotype. Protein interaction assays showed that these four GmCHLIs can interact with each other, but stronger interactions were found with mutated subunits. The results indicate that, in polyploidy, deficiency in each copy of duplicated oligomer-encoding genes could result in a mutant phenotype due to hetero-oligomer formation, which is different from the model of allelic dosage or functional redundancy. In addition, we interestingly found an increase in isoflavonoids in the heterozygous etiolated plants, which might be useful for improving soybean seed quality.
多倍体在自然界中很普遍。由于当编码的蛋白质作为寡聚体发挥作用时，重复基因的命运会变得更加复杂，因此对多倍体基因组中重复的寡聚体编码基因进行功能研究将有助于我们理解性状是如何表达的。在本研究中，我们鉴定出了GmCHLI1，这是一个编码镁（Mg）螯合酶I亚基的基因，该亚基以六聚体形式发挥作用，导致大豆出现半显性黄化表型。在大豆基因组中鉴定出了四个源自两次多倍体事件的GmCHLI拷贝。对表达模式的进一步研究表明，这四个拷贝已分化为两对；包含GmCHLI1的那一对中的另一个拷贝发生突变也会导致叶绿素缺乏表型。蛋白质相互作用分析表明，这四个GmCHLI可以相互作用，但发现与突变亚基的相互作用更强。结果表明，在多倍体中，由于异源寡聚体的形成，重复的寡聚体编码基因的每个拷贝的缺陷都可能导致突变表型，这与等位基因剂量或功能冗余模型不同。此外，我们有趣地发现杂合黄化植物中的异黄酮含量增加，这可能有助于提高大豆种子质量。
