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小立碗藓FTR1基因家族进化分析及铁胁迫下的功能研究

Evolutionary analysis of the FTR1 gene family in Physcomitrium patens (Hedw.) Mitt and its function under iron stress

  • 摘要: 高亲和性铁通透酶(Fe transporter 1,high-affinity iron permease,FTR1)是能够将Fe3+转运到细胞内的重要铁转运蛋白。本文对早期陆生植物小立碗藓(Physcomitrium patens (Hedw.) Mitt)开展了FTR1基因家族成员鉴定、序列分析、亚细胞定位及铁胁迫响应等相关研究。结果显示,PpFTR1基因家族共3个成员(PpFTR1-1PpFTR1-2PpFTR1-3),分别位于15、21和22号染色体上,三者所编码蛋白均包含保守的REXXE铁离子结合基序,但PpFTR1-3蛋白的第2个REXXE基序发生了变异。生物信息学预测结果显示,PpFTR1为跨膜蛋白,且均定位于细胞膜,蛋白亚细胞定位实验也证实了该预测。此外,PpFTR1-1PpFTR1-2基因在缺铁以及过量铁处理下均有明显上调,而PpFTR1-3基因则无明显变化。系统进化分析结果表明,FTR1家族在植物界主要分布在绿藻、轮藻及早期陆生植物中,但在种子植物中全部丢失。且相比陆生植物的祖先——轮藻,早期陆生植物与真菌FTR1家族的系统关系更近,推测早期陆生植物FTR1的起源可能与真菌互作有关。

     

    Abstract: Fe Transporter 1 (FTR1), a high-affinity iron permease, facilitates the uptake of ferric ion (Fe3+) into cells. This study investigated the FTR1 gene family in the early terrestrial plant Physcomitrium patens (Hedw.) Mitt., integrating genome-wide identification, sequence analysis, evolutionary inference, subcellular localization, and expression profiling under iron stress. Three members of the PpFTR1 gene family (PpFTR1-1, PpFTR1-2, and PpFTR1-3) were mapped to chromosomes 15, 21, and 22, respectively. All three genes encoded proteins that contained the conserved REXXE Fe-binding motif; however, the second REXXE motif in the PpFTR1-3 protein was mutated. Bioinformatics analysis and protein subcellular localization experiments indicated that all three transmembrane proteins localized to the cell membrane. The PpFTR1-1 and PpFTR1-2 genes were significantly upregulated in response to both iron deficiency and iron excess, whereas PpFTR1-3 remained unresponsive. Phylogenetic analysis revealed that the FTR1 family is predominantly distributed in green algae, charophytes, and early terrestrial plants (e.g., mosses and ferns), with homologous FTR1 sequences entirely absent in seed plants. Notably, FTR1 sequences from early terrestrial plants exhibited closer evolutionary affinity to fungal homologs than to those of charophytes, the ancestral lineage of terrestrial plants, indicating a possible horizontal gene transfer event during terrestrialization. These findings not only provide a theoretical framework for understanding the molecular mechanisms by which early land plants adapted to iron stress but also offer insights into gene regulation mechanisms and the enhancement of iron uptake in crops.

     

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