The activation of calcium signaling is a crucial event for perceiving environmental stress. Colonization by Piriformospora indica, a growth-promoting root endosymbiont, activates cytosolic Ca2+ in Arabidopsis roots. In this study, we examined the role and functional relevance of calcium channels responsible for Ca2+ fluxes. Expression profiling revealed that CYCLIC NUCLEOTIDE GATED CHANNEL 19 (CNGC19) is an early-activated gene, induced by unidentified components in P. indica cell-wall extract. Functional analysis showed that loss-of-function of CNGC19 resulted in growth inhibition by P.indica, due to increased colonization and loss of controlled fungal growth. The cngc19 mutant showed reduced elevation of cytosolic Ca2+ in response to P. indica cell-wall extract in comparison to the wild-type. Microbe-associated molecular pattern-triggered immunity was compromised in the cngc19 lines, as evidenced by unaltered callose deposition, reduced cis-(+)-12-oxo-phytodienoic acid, jasmonate, and jasmonoyl isoleucine levels, and down-regulation of jasmonate and other defense-related genes, which contributed to a shift towards a pathogenic response. Loss-of-function of CNGC19 resulted in an inability to modulate indole glucosinolate content during P. indica colonization. CNGC19-mediated basal immunity was dependent on the AtPep receptor, PEPR. CNGC19 was also crucial for P. indica-mediated suppression of AtPep-induced immunity. Our results thus demonstrate that Arabidopsis CNGC19 is an important Ca2+ channel that maintains a robust innate immunity and is crucial for growth-promotion signaling upon colonization by P. indica.

中文翻译：

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钙通道 CNGC19 介导基础防御信号以调节拟南芥根中 Piriformospora indica 的定植。

钙信号的激活是感知环境压力的关键事件。Piriformospora indica（一种促进生长的根内共生体）的定殖激活了拟南芥根中的细胞溶质 Ca2+。在这项研究中，我们检查了负责 Ca2+ 通量的钙通道的作用和功能相关性。表达谱显示环状核苷酸门控通道 19 (CNGC19) 是一种早期激活基因，由籼稻细胞壁提取物中的未知成分诱导。功能分析表明，CNGC19 的功能丧失导致 P.indica 的生长抑制，这是由于定植增加和受控真菌生长的丧失。与野生型相比，cngc19 突变体响应于 P. indica 细胞壁提取物的细胞溶质 Ca2+ 升高降低。微生物相关分子模式触发的免疫在 cngc19 系中受到损害，如未改变的胼胝质沉积、顺式-(+)-12-氧代植物二烯酸、茉莉酸和茉莉酸异亮氨酸水平降低以及茉莉酸和其他与防御相关的基因，这有助于向致病反应转变。CNGC19 的功能丧失导致在 P. indica 定植期间无法调节吲哚芥子油苷含量。CNGC19 介导的基础免疫依赖于 AtPep 受体 PEPR。CNGC19 对 P. indica 介导的 AtPep 诱导的免疫抑制也是至关重要的。因此，我们的研究结果表明，拟南芥 CNGC19 是一种重要的 Ca2+ 通道，可维持强大的先天免疫，并且对于 P. indica 定植后的生长促进信号传导至关重要。