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Ethylene is an important plant hormone that regulates numerous cellular processes and stress responses. The mode of action of ethylene is both dose-and time-dependent. Protein phosphorylation plays a key role in ethylene signaling, which is mediated by the activities of ethylene receptors, constitutive triple response 1 (CTR1) kinase, and phosphatase. To address how ethylene alters the cellular protein phosphorylation profile in a time-dependent manner, differential and quantitative phosphoproteomics based on 15 N stable isotope labeling in Arabidopsis was performed on both one-minute ethylene-treated Arabidopsis ethylene-overly-sensitive loss-of-function mutant rcn1-1, deficient in PP2A phosphatase activity, and a pair of long-term ethylene-treated wild-type and loss-of-function ethylene signaling ctr1-1 mutants, deficient in mitogen-activated kinase kinase kinase activity. In total, 1079 phosphopeptides were identified, among which 44 were novel. Several one-minute ethylene-regulated phosphoproteins were found from the rcn1-1. Bioinformatic analysis of the rcn1-1 phosphoproteome predicted nine phosphoproteins as the putative substrates for PP2A phosphatase. In addition, from CTR1 kinase-enhanced phosphosites, we also found putative CTR1 kinase substrates including plastid transcriptionally active protein and calcium-sensing receptor. These regulatory proteins are phosphorylated in the presence of ethylene. Analysis of ethyleneregulated phosphosites using the group-based prediction system with a protein-protein interaction filter revealed a total of 14 kinase-substrate relationships that may function in both CTR1 kinase-and PP2A phosphatase-mediated phosphor-relay pathways. Ethylene is a volatile plant hormone that regulates versatile molecular and physiological processes in higher plants (1). The perception of this gaseous two-carbon hormone is achieved by a group of membrane-associated dimeric ethylene receptors that resemble bacterial two-component signaling systems and are composed of hybrid histidine (or aspartic acid) kinases, a histidine-containing phosphor-transfer domain, and response regulators (2). These receptors are made of two membrane-bound protein subunits cross-linked at the N-terminal region through two disulfide bonds (3). In Arabidopsis, there are five different ethylene receptor subunits: ethylene response 1, ethylene response 2, ethylene insensitive 4 (EIN4), 1 ethylene response sensor 1, and ethylene re- 1 The abbreviations used are: ACC, aminocyclopropane-1-carboxylic acid; ACN, acetonitrile; CIPK1, CBL-interacting protein kinase 1; CTR1, constitutive triple response 1; eer1-1, enhanced ethylene response 1; EIN, ethylene insensitive; FBH3, flowering bHLH 3 protein; FDR, false discovery rate; GPS, group-based prediction system; HMG, high mobility group; IMAC, immobilized metal-ion-affinity chromatography; iTRAQ, isobaric tag for relative and absolute quantitation; LHCB, light harvetsting chlorophyll A/B binding protein; Research

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The authors' results suggest that CI causes a frequency-specific disruption in resting-state connectivity. This may be useful for assessing the effectiveness of functional recovery after CI.

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This study investigated the ion mobility (IM) and the collision cross section (CCS) of fatty acids (FAs) using electrospray IM MS. The IM analysis of 18 FA ions showed intriguing differences among the saturated FAs, monounsaturated FAs, multi-unsaturated FAs, and cis-isomer/trans-isomer with respect to the aliphatic tail chains. The length of aliphatic tail chain present in the ion structures had a strong influence on the differentiation of drift, while the number of double bond showed a weaker influence. The tiny drift differences between cis-isomer and trans-isomer were also observed. In the CCS measurements, two internal standards were involved in the mobility calibration and accuracy estimation. It insured our empirical CCS values were of high experimental precision (±0.35% or better) and accuracy (±0.25% or better). Moreover, the mass-to-charge ratio (m/z) - mobility plots obtained by ion mobility spectrometry with mass spectrometry analysis of FAs - was used to investigate the structural relationship between the molecules. Each series of FAs sharing a similar structure was aligned in the linear plot. Finally, the developed procedure was applied to the determination of FAs in rat adipose tissues, and it allowed the presence of 13 FAs to be confirmed with their exact masses and CCS values. These studies reveal the direct relationship between the behaviors in IM and the molecular structures and thus may provide further validations to the FA identification process.