Host-related metabolic cues affect colonization strategies of a root endophyte
Host-related metabolic cues affect colonization strategies of a root endophyte
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DOI：
10.1073/pnas.1301653110
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发表时间：
2013-08-20
影响因子：
11.1
通讯作者：
Zuccaro, Alga
中科院分区：
文献类型：
--
作者：
Lahrmann, Urs;Ding, Yi;Zuccaro, Alga
根共生中广泛相容性的基础机制在很大程度上尚未探索。多面手根内生菌Piriformospora indica与形态学和生物化学上不同的宿主建立持久的相互作用，刺激它们的生长，减轻盐胁迫，并诱导对病原体的局部和系统抗性。细胞学研究和全球调查的真菌转录反应的殖民大麦和拟南芥在不同的共生阶段确定主机依赖的殖民策略和主机特异性诱导的效应候选人。在这里，我们表明，在拟南芥中，P.印度建立和维持活体营养活表皮细胞内，而在大麦的共生体经历了营养开关腐营养，这是与生产的次生较薄的菌丝在死皮层细胞。与多样化的营养行为，并与发生在大麦中的腐生性的氮缺乏，真菌基因编码的水解酶和营养转运蛋白的高度诱导在这个主机，但不是在拟南芥。沉默的高亲和力的铵转运蛋白PiAMT1基因，其成绩单积累在氮饥饿和大麦，导致增强殖民化的主机，而它没有影响拟南芥的殖民化。在定殖的大麦根中，细胞死亡标记物VPE（液泡加工酶）的游离氨基酸水平增加和酶活性降低与PiAMT1沉默后P. indica的延长的活体营养生活方式相一致。这表明，PiAmt1作为一个氮传感器介导的信号，触发在植物中激活的腐食性程序。因此，宿主相关的代谢线索影响了印度豹的替代生活方式的表达。
The mechanisms underpinning broad compatibility in root symbiosis are largely unexplored. The generalist root endophyte Piriformospora indica establishes long-lasting interactions with morphologically and biochemically different hosts, stimulating their growth, alleviating salt stress, and inducing local and systemic resistance to pathogens. Cytological studies and global investigations of fungal transcriptional responses to colonization of barley and Arabidopsis at different symbiotic stages identified host-dependent colonization strategies and host-specifically induced effector candidates. Here, we show that in Arabidopsis, P. indica establishes and maintains biotrophic nutrition within living epidermal cells, whereas in barley the symbiont undergoes a nutritional switch to saprotrophy that is associated with the production of secondary thinner hyphae in dead cortex cells. Consistent with a diversified trophic behavior and with the occurrence of nitrogen deficiency at the onset of saprotrophy in barley, fungal genes encoding hydrolytic enzymes and nutrient transporters were highly induced in this host but not in Arabidopsis. Silencing of the high-affinity ammonium transporter PiAMT1 gene, whose transcripts are accumulating during nitrogen starvation and in barley, resulted in enhanced colonization of this host, whereas it had no effect on the colonization of Arabidopsis. Increased levels of free amino acids and reduced enzymatic activity for the cell-death marker VPE (vacuolar-processing enzyme) in colonized barley roots coincided with an extended biotrophic lifestyle of P. indica upon silencing of PiAMT1. This suggests that PiAmt1 functions as a nitrogen sensor mediating the signal that triggers the in planta activation of the saprotrophic program. Thus, host-related metabolic cues affect the expression of P. indica's alternative lifestyles.