The H+-ATPase HA1 of Medicago truncatula Is Essential for Phosphate Transport and Plant Growth during Arbuscular Mycorrhizal Symbiosis
The H+-ATPase HA1 of Medicago truncatula Is Essential for Phosphate Transport and Plant Growth during Arbuscular Mycorrhizal Symbiosis
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DOI：
10.1105/tpc.113.120436
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发表时间：
2014-04-01
期刊：
影响因子：
11.6
通讯作者：
Hause, Bettina
中科院分区：
文献类型：
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作者：
Krajinski, Franziska;Courty, Pierre-Emmanuel;Hause, Bettina
丛枝菌根共生的关键特征是通过菌根途径改善宿主植物的磷营养，即，真菌从土壤中吸收磷和从根细胞内的丛枝中释放磷。Pi从真菌到植物细胞的有效运输被认为需要穿过将真菌丛枝与宿主细胞质分离的丛枝周膜（PAM）的质子梯度。研究表明，H~+-ATPase基因HA1在蒺藜苜蓿含丛枝的根细胞中特异表达。我们分离到一株ha1 - 2突变株。truncatula，发现它是受损的发展丛枝，但不是根定植Rhizophagus irregularis菌丝。HA1的人工microRNA沉默重现了这种表型，导致小的和截短的丛枝。与野生型不同，ha1 - 2突变体未能表现出积极的生长反应，菌根定植在Pi限制条件下。吸收实验证实ha1 - 2突变体不能通过菌根途径吸收磷。与野生型相比，在含有ha1 - 2突变体的细胞的异常丛枝的质外体中增加的pH表明，HA1对于在PAM上建立质子梯度是至关重要的，因此对于Pi从真菌转移到植物是不可或缺的。
A key feature of arbuscular mycorrhizal symbiosis is improved phosphorus nutrition of the host plant via the mycorrhizal pathway, i.e., the fungal uptake of Pi from the soil and its release from arbuscules within root cells. Efficient transport of Pi from the fungus to plant cells is thought to require a proton gradient across the periarbuscular membrane (PAM) that separates fungal arbuscules from the host cell cytoplasm. Previous studies showed that the H+-ATPase gene HA1 is expressed specifically in arbuscule containing root cells of Medicago truncatula. We isolated a ha1-2 mutant of M. truncatula and found it to be impaired in the development of arbuscules but not in root colonization by Rhizophagus irregularis hyphae. Artificial microRNA silencing of HA1 recapitulated this phenotype, resulting in small and truncated arbuscules. Unlike the wild type, the ha1-2 mutant failed to show a positive growth response to mycorrhizal colonization under Pi-limiting conditions. Uptake experiments confirmed that ha1-2 mutants are unable to take up phosphate via the mycorrhizal pathway. Increased pH in the apoplast of abnormal arbuscule containing cells of the ha1-2 mutant compared with the wild type suggests that HA1 is crucial for building a proton gradient across the PAM and therefore is indispensible for the transfer of Pi from the fungus to the plant.