College of Life Science and Technology, State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.
Fungal Biol. 2013 Jan;117(1):22-31. doi: 10.1016/j.funbio.2012.11.002. Epub 2012 Nov 30.
Fluctuations in intracellular calcium levels generate signalling events and regulate different cellular processes. Whilst the implication of Ca(2+) in plant responses during arbuscular mycorrhiza (AM) interactions is well documented, nothing is known about the regulation or role of this secondary messenger in the fungal symbiont. The spatio-temporal expression pattern of putatively Ca(2+)-related genes of Glomus intraradices BEG141 encoding five proteins involved in membrane transport and one nuclear protein kinase, was investigated during the AM symbiosis. Expression profiles related to successful colonization of host roots were observed in interactions of G. intraradices with roots of wild-type Medicago truncatula (line J5) compared to the mycorrhiza-defective mutant dmi3/Mtsym13. Symbiotic fungal activity was monitored using stearoyl-CoA desaturase and phosphate transporter genes. Laser microdissection based-mapping of fungal gene expression in mycorrhizal root tissues indicated that the Ca(2+)-related genes were differentially upregulated in arbuscules and/or in intercellular hyphae. The spatio-temporal variations in gene expression suggest that the encoded proteins may have different functions in fungal development or function during symbiosis development. Full-length cDNA obtained for two genes with interesting expression profiles confirmed a close similarity with an endoplasmic reticulum P-type ATPase and a Vcx1-like vacuolar Ca(2+) ion transporter functionally characterized in other fungi and involved in the regulation of cell calcium pools. Possible mechanisms are discussed in which Ca(2+)-related proteins G. intraradices BEG141 may play a role in mobilization and perception of the intracellular messenger by the AM fungus during symbiotic interactions with host roots.
细胞内钙离子水平的波动会产生信号事件，并调节不同的细胞过程。虽然 Ca(2+) 在丛枝菌根（AM）相互作用中对植物反应的影响已有详细记录，但对于这种第二信使在真菌共生体中的调节或作用仍一无所知。本研究调查了 Glomus intraradices BEG141 中与 Ca(2+) 相关的假定基因的时空表达模式，该基因编码参与膜转运的 5 种蛋白和 1 种核蛋白激酶，在 AM 共生中。与根瘤菌缺陷突变体 dmi3/Mtsym13 相比，在与野生型 Medicago truncatula（J5 系）根的相互作用中观察到与成功定殖宿主根相关的表达谱。共生真菌活性通过硬脂酰辅酶 A 去饱和酶和磷酸盐转运体基因进行监测。基于激光微切割的真菌基因表达在共生根组织中的定位表明，Ca(2+)-相关基因在丛枝和/或细胞间菌丝中差异上调。基因表达的时空变化表明，编码蛋白在真菌发育或共生体发育过程中的功能中可能具有不同的功能。获得的具有有趣表达谱的两个基因的全长 cDNA 证实与内质网 P 型 ATP 酶和 Vcx1 样液泡 Ca(2+) 离子转运体具有密切相似性，该转运体在其他真菌中具有功能，并参与细胞钙池的调节。讨论了 Ca(2+)-相关蛋白 G. intraradices BEG141 可能在 AM 真菌与宿主根共生相互作用中通过动员和感知细胞内信使在丛枝菌根共生中的作用的可能机制。
