Chitinase-resistant hydrophilic symbiotic factors secreted by Frankia activate both Ca2+ spiking and NIN gene expression in the actinorhizal plant Casuarina glauca
Chitinase-resistant hydrophilic symbiotic factors secreted by Frankia activate both Ca2+ spiking and NIN gene expression in the actinorhizal plant Casuarina glauca
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DOI：
10.1111/nph.13732
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发表时间：
2016-01-01
期刊：
影响因子：
9.4
通讯作者：
Svistoonoff, Sergio
中科院分区：
文献类型：
--
作者：
Chabaud, Mireille;Gherbi, Hassen;Svistoonoff, Sergio
尽管现在已经确定装饰脂壳低聚糖Nod因子是在宿主豆类物种中启动感染/结瘤的关键根瘤菌信号，但Frankia/放线菌关联中等效微生物信号分子的身份仍然难以捉摸。为了识别Frankia共生因子，我们提出了一种基于模型放线菌物种Casuarina glauca中表达的分子和细胞感染前报告基因的新方法。将核定位的cameleon Nup-YC2.1引入木麻黄中，我们发现相容的Frankia CcI3菌株的无细胞培养物上清液能够在宿主根毛中引发持续的高频Ca2+尖峰。此外，作为测试的 Frankia 菌株的函数，核 Ca2+ 尖峰的触发和 ProCgNIN:GFP 报告基因的转录激活之间存在极好的相关性。这两种感染前的共生反应结合起来使用，表明 Frankia CcI3 上清液中存在的信号分子是亲水性的、低分子量的，并且能抵抗几丁质酶降解。 总之，Frankia 分泌的生物活性共生信号在化学上似乎与目前已知的基于几丁质的根瘤菌/丛枝菌根信号分子不同。现在可以对木麻黄进行方便的生物测定，以对其进行全面表征。
Although it is now well-established that decorated lipo-chitooligosaccharide Nod factors are the key rhizobial signals which initiate infection/nodulation in host legume species, the identity of the equivalent microbial signaling molecules in the Frankia/actinorhizal association remains elusive.With the objective of identifying Frankia symbiotic factors we present a novel approach based on both molecular and cellular pre-infection reporters expressed in the model actinorhizal species Casuarina glauca.By introducing the nuclear-localized cameleon Nup-YC2.1 into Casuarina glauca we show that cell-free culture supernatants of the compatible Frankia CcI3 strain are able to elicit sustained high frequency Ca2+ spiking in host root hairs. Furthermore, an excellent correlation exists between the triggering of nuclear Ca2+ spiking and the transcriptional activation of the ProCgNIN:GFP reporter as a function of the Frankia strain tested. These two pre-infection symbiotic responses have been used in combination to show that the signal molecules present in the Frankia CcI3 supernatant are hydrophilic, of low molecular weight and resistant to chitinase degradation.In conclusion, the biologically active symbiotic signals secreted by Frankia appear to be chemically distinct from the currently known chitin-based rhizobial/arbuscular mycorrhizal signaling molecules. Convenient bioassays in Casuarina glauca are now available for their full characterization.