Center for Genomics and Biotechnology, Haixia Institute of Science and Technology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, College of Resources and Environment, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Guangxi Key Lab of Sugarcane Biology, Guangxi University, Nanning, Guangxi, China.
BMC Genomics. 2019 Jan 24;20(1):83. doi: 10.1186/s12864-019-5437-3.
Sugarcane served as the model plant for discovery of the C photosynthetic pathway. Magnesium is the central atom of chlorophyll, and thus is considered as a critical nutrient for plant development and photosynthesis. In plants, the magnesium transporter (MGT) family is composed of a number of membrane proteins, which play crucial roles in maintaining Mg homeostasis. However, to date there is no information available on the genomics of MGTs in sugarcane due to the complexity of the Saccharum genome.
Here, we identified 10 MGTs from the Saccharum spontaneum genome. Phylogenetic analysis of MGTs suggested that the MGTs contained at least 5 last common ancestors before the origin of angiosperms. Gene structure analysis suggested that MGTs family of dicotyledon may be accompanied by intron loss and pseudoexon phenomena during evolution. The pairwise synonymous substitution rates corresponding to a divergence time ranged from 142.3 to 236.6 Mya, demonstrating that the MGTs are an ancient gene family in plants. Both the phylogeny and Ks analyses indicated that SsMGT1/SsMGT2 originated from the recent ρWGD, and SsMGT7/SsMGT8 originated from the recent σ WGD. These 4 recently duplicated genes were shown low expression levels and assumed to be functionally redundant. MGT6, MGT9 and MGT10 weredominant genes in the MGT family and werepredicted to be located inthe chloroplast. Of the 3 dominant MGTs, SsMGT6 expression levels were found to be induced in the light period, while SsMGT9 and SsMTG10 displayed high expression levels in the dark period. These results suggested that SsMGT6 may have a function complementary to SsMGT9 and SsMTG10 that follows thecircadian clock for MGT in the leaf tissues of S. spontaneum. MGT3, MGT7 and MGT10 had higher expression levels Insaccharum officinarum than in S. spontaneum, suggesting their functional divergence after the split of S. spontaneum and S. officinarum.
This study of gene evolution and expression of MGTs in S. spontaneum provided basis for the comprehensive genomic study of the entire MGT genes family in Saccharum. The results are valuable for further functional analyses of MGT genes and utilization of the MGTs for Saccharum genetic improvement.
甘蔗是发现 C 光合作用途径的模式植物。镁是叶绿素的中心原子，因此被认为是植物发育和光合作用的关键营养物质。在植物中，镁转运蛋白（MGT）家族由许多膜蛋白组成，这些蛋白在维持镁稳态中起着至关重要的作用。然而，由于甘蔗基因组的复杂性，迄今为止，关于甘蔗 MGT 的基因组学信息尚不清楚。
在这里，我们从甜根子草基因组中鉴定了 10 个 MGT。MGT 的系统发育分析表明，MGT 至少包含 5 个在被子植物起源之前的最后共同祖先。基因结构分析表明，在进化过程中，双子叶植物的 MGT 家族可能伴随着内含子缺失和假外显子现象。对应于分化时间的成对同义替换率范围为 142.3 至 236.6 Mya，表明 MGT 是植物中的一个古老基因家族。系统发育和 Ks 分析均表明，SsMGT1/SsMGT2 起源于最近的 ρWGD，SsMGT7/SsMGT8 起源于最近的 σWGD。这 4 个最近复制的基因表现出低表达水平，假定具有功能冗余性。MGT6、MGT9 和 MGT10 是 MGT 家族中的优势基因，预测定位于叶绿体中。在这 3 个主要的 MGT 中，SsMGT6 的表达水平在光照期被诱导，而 SsMGT9 和 SsMTG10 在暗期表达水平较高。这些结果表明，SsMGT6 可能具有与 SsMGT9 和 SsMTG10 互补的功能，遵循生物钟，在甜根子草叶片组织中对 MGT 起作用。MGT3、MGT7 和 MGT10 在甘蔗中的表达水平高于甜根子草，表明它们在甜根子草和甘蔗分离后发生了功能分化。
本研究对甜根子草 MGT 的基因进化和表达进行了研究，为甘蔗整个 MGT 基因家族的综合基因组研究提供了基础。这些结果对进一步研究 MGT 基因的功能以及利用 MGT 进行甘蔗遗传改良具有重要价值。
