Control of basal jasmonate signalling and defence through modulation of intracellular cation flux capacity

Corresponding author: Edward E. Farmer

• Unknown mechanisms tightly regulate the basal activity of the wound-inducible defence mediator jasmonate (JA) in undamaged tissues. However, the Arabidopsis fatty acid oxygenation upregulated2 (fou2) mutant in vacuolar two-pore channel 1 (液泡双孔道; TPC1D454N) displays high JA pathway activity in undamaged leaves. This mutant was used to explore mechanisms controlling basal JA pathway regulation.

• fou2 was re-mutated to generate novel ‘ouf’ suppressor mutants. Patch-clamping (膜片钳; 又称单通道电流记录技术) was used to examine TPC1 cation channel (阳离子通道) characteristics in the ouf suppressor mutants and in fou2. Calcium (Ca2+) imaging was used to study the effects fou2 on cytosolic (胞浆) Ca2+ concentrations.

• Six intragenic (基因内的) ouf suppressors with near wild-type (WT) JA pathway activity were recovered (恢复) and one mutant, ouf8, affected the channel pore (通道孔). At low luminal (腔) calcium concentrations, ouf8 had little detectable effect on fou2. However, increased vacuolar Ca2+ concentrations caused channel occlusion (闭塞), selectively blocking K+ fluxes towards the cytoplasm (细胞质). Cytosolic Ca2+ concentrations in unwounded fou2 were found to be lower than in the unwounded WT, but they increased in a similar manner in both genotypes following wounding.

• Basal JA pathway activity can be controlled solely (唯一地) by manipulating endomembrane (内膜) cation flux capacities. We suggest that changes in endomembrane potential affect JA pathway activity.

一些未知的分子机制在调控在未受伤组织中由创伤诱导的防御介质JA的活性。然而，拟南芥中在液泡双孔道TPC1中的脂肪酸氧化上调fou2突变体显示在未受伤的叶片中会有较高的JA通路活性。该突变体被用于探究控制JA通路调控的研究。

fou2又被再次突变用以产生新的ouf抑制突变体。膜片钳被用来研究在ouf抑制突变体和fou2突变体中TPC1阳离子通道的特性。钙离子成像技术被用以研究fou2在胞浆钙离子浓度的作用。

六个基因内ouf抑制突变体和一个ouf8突变体影响了通道孔。在低的腔钙离子浓度下，ouf8对于fou2几乎没有抑制作用。然而，液泡的钙离子浓度增加后会引起通道的闭塞，选择性地阻断钾离子向细胞质的通量。在未受伤的fou2突变体中胞浆钙离子浓度要比未受伤的野生型要低，但在创伤后这两者钙离子浓度升高的情况类似。

通讯：Edward E. Farmer (http://www.unil.ch/dbmv/en/home/menuinst/recherche/prof-edward-farmer.html)

doi: 10.1111/nph.14754

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