State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China.
Root Biology Center, Fujian Agriculture and Forestry University, Fuzhou, China.
Plant Cell Environ. 2019 Jun;42(6):2015-2027. doi: 10.1111/pce.13530. Epub 2019 Mar 5.
Arbuscules are the central structures of the symbiotic association between terrestrial plants and arbuscular mycorrhizal (AM) fungi. However, arbuscules are also ephemeral structures, and following development, these structures are soon digested and ultimately disappear. Currently, little is known regarding the mechanism underlying the digestion of senescent arbuscules. Here, biochemical and functional analyses were integrated to test the hypothesis that a purple acid phosphatase, GmPAP33, controls the hydrolysis of phospholipids during arbuscule degeneration. The expression of GmPAP33 was enhanced by AM fungal inoculation independent of the P conditions in soybean roots. Promoter-β-glucuronidase (GUS) reporter assays revealed that the expression of GmPAP33 was mainly localized to arbuscule-containing cells during symbiosis. The recombinant GmPAP33 exhibited high hydrolytic activity towards phospholipids, phosphatidylcholine, and phosphatidic acid. Furthermore, soybean plants overexpressing GmPAP33 exhibited increased percentages of large arbuscules and improved yield and P content compared with wild-type plants when inoculated with AM fungi. Mycorrhizal RNAi plants had high phospholipid levels and a large percentage of small arbuscules. These results in combination with the subcellular localization of GmPAP33 at the plasma membrane indicate that GmPAP33 participates in arbuscule degeneration during AM symbiosis via involvement in phospholipid hydrolysis.
丛枝菌根真菌与陆生植物共生的中心结构是丛枝。然而，丛枝也是短暂的结构，在发育后，这些结构很快被消化，最终消失。目前，关于衰老丛枝消化的机制知之甚少。本研究整合了生化和功能分析，以检验紫色酸性磷酸酶 GmPAP33 控制丛枝退化过程中磷脂水解的假设。AM 真菌接种后，GmPAP33 的表达增强，而与大豆根中的 P 条件无关。启动子-β-葡萄糖醛酸酶（GUS）报告基因分析表明，GmPAP33 的表达主要定位于共生过程中的丛枝细胞中。重组 GmPAP33 对磷脂、磷脂酰胆碱和磷脂酸表现出很高的水解活性。此外，与野生型植物相比，过表达 GmPAP33 的大豆植物在接种 AM 真菌时表现出较大丛枝的比例增加，产量和 P 含量提高。Mycorrhizal RNAi 植物具有较高的磷脂水平和较大比例的小丛枝。这些结果与 GmPAP33 在质膜上的亚细胞定位相结合，表明 GmPAP33 通过参与磷脂水解参与 AM 共生中的丛枝退化。
