Rizal Govinda, Karki Shanta, Thakur Vivek, Wanchana Samart, Alonso-Cantabrana Hugo, Dionora Jacque, Sheehy John E, Furbank Robert, von Caemmerer Susanne, Quick William Paul
C4 Rice Center, IRRI, Los Banos, Laguna, the Philippines.
Government of Nepal, Ministry of Agricultural Development, Kathmandu, Nepal.
PLoS One. 2017 Jun 22;12(6):e0179567. doi: 10.1371/journal.pone.0179567. eCollection 2017.
Recent efforts to engineer C4 photosynthetic traits into C3 plants such as rice demand an understanding of the genetic elements that enable C4 plants to outperform C3 plants. As a part of the C4 Rice Consortium's efforts to identify genes needed to support C4 photosynthesis, EMS mutagenized sorghum populations were generated and screened to identify genes that cause a loss of C4 function. Stable carbon isotope ratio (δ13C) of leaf dry matter has been used to distinguishspecies with C3 and C4 photosynthetic pathways. Here, we report the identification of a sorghum (Sorghum bicolor) mutant with a low δ13C characteristic. A mutant (named Mut33) with a pale phenotype and stunted growth was identified from an EMS treated sorghum M2 population. The stable carbon isotope analysis of the mutants showed a decrease of 13C uptake capacity. The noise of random mutation was reduced by crossing the mutant and its wildtype (WT). The back-cross (BC1F1) progenies were like the WT parent in terms of 13C values and plant phenotypes. All the BC1F2 plants with low δ13C died before they produced their 6th leaf. Gas exchange measurements of the low δ13C sorghum mutants showed a higher CO2 compensation point (25.24 μmol CO2.mol-1air) and the maximum rate of photosynthesis was less than 5μmol.m-2.s-1. To identify the genetic determinant of this trait, four DNA pools were isolated; two each from normal and low δ13C BC1F2 mutant plants. These were sequenced using an Illumina platform. Comparison of allele frequency of the single nucleotide polymorphisms (SNPs) between the pools with contrasting phenotype showed that a locus in Chromosome 10 between 57,941,104 and 59,985,708 bps had an allele frequency of 1. There were 211 mutations and 37 genes in the locus, out of which mutations in 9 genes showed non-synonymous changes. This finding is expected to contribute to future research on the identification of the causal factor differentiating C4 from C3 species that can be used in the transformation of C3 to C4 plants.
最近，人们致力于将C4光合特性引入水稻等C3植物中，这需要了解使C4植物比C3植物表现更优的遗传因素。作为C4水稻联盟识别支持C4光合作用所需基因工作的一部分，研究人员构建并筛选了经甲基磺酸乙酯（EMS）诱变的高粱群体，以识别导致C4功能丧失的基因。叶片干物质的稳定碳同位素比率（δ13C）已被用于区分具有C3和C4光合途径的物种。在此，我们报告了一个具有低δ13C特征的高粱（双色高粱）突变体的识别情况。从经EMS处理的高粱M2群体中鉴定出一个表型苍白且生长发育迟缓的突变体（命名为Mut33）。对这些突变体的稳定碳同位素分析表明其13C吸收能力下降。通过使突变体与其野生型（WT）杂交，降低了随机突变的干扰。回交（BC1F1）后代在13C值和植株表型方面与野生型亲本相似。所有δ13C值低的BC1F2植株在长出第6片叶之前就死亡了。对低δ13C高粱突变体的气体交换测量显示，其二氧化碳补偿点较高（25.24 μmol CO2·mol-1空气），最大光合速率小于5 μmol·m-2·s-1。为了识别该性状的遗传决定因素，分离了四个DNA池；两个来自正常的BC1F2突变体植株，两个来自低δ13C的BC1F2突变体植株。使用Illumina平台对它们进行测序。比较具有不同表型的池之间单核苷酸多态性（SNP）的等位基因频率，结果显示10号染色体上57,941,104至59,985,708碱基对之间的一个位点的等位基因频率为1。该位点有211个突变和37个基因，其中9个基因的突变显示非同义变化。这一发现有望为未来识别区分C4和C3物种的因果因素的研究做出贡献，这些因素可用于将C3植物转化为C4植物。
