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In plants, a local infection can lead to systemic acquired resistance (SAR) through increased production of salicylic acid (SA). For many years, the identity of the mobile signal and its direct transduction mechanism for systemic SA synthesis in initiating SAR have been debated. We found that in Arabidopsis thaliana, after a local infection, the conserved cysteine residue of the transcription factor CCA1 HIKING EXPEDITION (CHE) undergoes sulfenylation in systemic tissues, which enhances its binding to the promoter of the SA-synthesis gene ISOCHORISMATE SYNTHASE1 (ICS1) and increases SA production. Furthermore, hydrogen peroxide (H2O2) produced through NADPH oxidases is the mobile signal that sulfenylates CHE in a concentration-dependent manner. Accumulation of SA and the previously reported signal molecules, such as N-hydroxypipecolic acid (NHP), then form a signal amplification loop to establish SAR. 

Abstract Graphene-based electrodes have been extensively investigated for supercapacitor applications. However, their ion diffusion efficiency is often hindered by the graphene restacking phenomenon. Even though holey graphene is fabricated to address this issue by providing ion transport channels, those channels could still be blocked by densely stacked graphene nanosheets. To tackle this challenge, this research aims at improving the ion diffusion efficiency of microwave-synthesized holey graphene films by tuning the water interlayer spacer towards the improved supercapacitor performance. By controlling the vacuum filtration during graphene-based electrode fabrication, we obtain dry films with dense packing and wet films with sparse packing. The SEM images reveal that 20 times larger interlayer distance is constructed in the wet film compared to that in the dry counterpart. The holey graphene wet film delivers a specific capacitance of 239 F/g, ~82% enhancement over the dry film (131 F/g). By an integrated experimental and computational study, we quantitatively show that the interlayer spacing in combination with the nanoholes in the basal plane dominates the ion diffusion rate in holey graphene-based electrodes. Our study concludes that novel hierarchical structures should be further considered even in holey graphene thin films to fully exploit the superior advantages of graphene-based supercapacitors.