Banasiak Joanna, Borghi Lorenzo, Stec Natalia, Martinoia Enrico, Jasiński Michał
Department of Plant Molecular Physiology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland.
Front Plant Sci. 2020 Feb 7;11:18. doi: 10.3389/fpls.2020.00018. eCollection 2020.
Strigolactones (SLs) are plant-derived signaling molecules that stimulate the hyphal branching of arbuscular mycorrhizal fungi (AMF), and consequently promote symbiotic interaction between the fungus and the plant. Currently, our knowledge on the molecular mechanism of SL transport is restricted to the family. In the family, SL translocation toward the rhizosphere occurs through the exodermis hypodermal passage cells and involves a member of the G subfamily, of the ATP-binding cassette (ABC) membrane transporters. Most species, including those that are agriculturally important, have a different root anatomy compared to most angiosperm plants (i.e., lacking an exodermis). Thus, we have investigated how SL transport occurs in the model legume . Here, we show that overexpression of a SL transporter from petunia (PaPDR1) enhances AMF colonization rates in . This result demonstrates the importance of ABCG proteins for the translocation of orobanchol-type molecules to facilitate arbuscular mycorrhiza, regardless of root anatomy and phylogenetic relationships. Moreover, our research has led to the identification of Medicago ABCG59, a close homologue of Petunia PDR1, that exhibits root specific expression and is up-regulated by phosphate starvation as well as in the presence of -GR24, a synthetic SL. Its promoter is active in cortical cells, root tips, and the meristematic zone of nodules. The loss-of-function mutant displayed a reduced level of mycorrhization compared to the WT plants but had no impact on the number of nodules after inoculation. The reduced mycorrhization indicates that less SLs are secreted by the mutant plants, which is in line with the observation that exudates exhibit a reduced stimulatory effect on the germination of the parasitic plant compared to the corresponding wild type.
独脚金内酯（SLs）是植物源信号分子，可刺激丛枝菌根真菌（AMF）的菌丝分支，从而促进真菌与植物之间的共生相互作用。目前，我们对SL转运分子机制的了解仅限于该家族。在该家族中，SL向根际的转运通过外皮层-皮下通道细胞进行，并且涉及ATP结合盒（ABC）膜转运蛋白的G亚家族成员。与大多数被子植物相比，包括那些具有重要农业意义的物种在内的大多数物种具有不同的根解剖结构（即缺乏外皮层）。因此，我们研究了SL在模式豆科植物中的转运方式。在这里，我们表明矮牵牛的SL转运蛋白（PaPDR1）过表达可提高其AMF定殖率。这一结果证明了ABCG蛋白对于促进独脚金醇型分子转运以促进丛枝菌根形成的重要性，而与根解剖结构和系统发育关系无关。此外，我们的研究还鉴定出了紫花苜蓿ABCG59，它是矮牵牛PDR1的紧密同源物，表现出根特异性表达，并且在缺磷以及存在合成SL类似物-GR24的情况下上调。其启动子在皮层细胞、根尖和根瘤分生组织区域具有活性。与野生型植物相比，该基因功能缺失突变体的菌根定殖水平降低，但接种后对根瘤数量没有影响。菌根定殖减少表明突变体植物分泌的SL较少，这与观察到的突变体分泌物与相应野生型相比对寄生植物种子萌发的刺激作用降低一致。
