A Plant DJ-1 Homolog Is Essential for Arabidopsis thaliana Chloroplast Development

Protein superfamilies can exhibit considerable diversification of function among their members in various organisms. The DJ-1 superfamily is composed of proteins that are principally involved in stress response and are widely distributed in all kingdoms of life. The model flowering plant Arabidopsis thaliana contains three close homologs of animal DJ-1, all of which are tandem duplications of the DJ-1 domain. Consequently, the plant DJ-1 homologs are likely pseudo-dimeric proteins composed of a single polypeptide chain. We report that one A. thaliana DJ-1 homolog (AtDJ1C) is the first DJ-1 homolog in any organism that is required for viability. Homozygous disruption of the AtDJ1C gene results in non-viable, albino seedlings that can be complemented by expression of wild-type or epitope-tagged AtDJ1C. The plastids from these dj1c plants lack thylakoid membranes and granal stacks, indicating that AtDJ1C is required for proper chloroplast development. AtDJ1C is expressed early in leaf development when chloroplasts mature, but is downregulated in older tissue, consistent with a proposed role in plastid development. In addition to its plant-specific function, AtDJ1C is an atypical member of the DJ-1 superfamily that lacks a conserved cysteine residue that is required for the functions of most other superfamily members. The essential role for AtDJ1C in chloroplast maturation expands the known functional diversity of the DJ-1 superfamily and provides the first evidence of a role for specialized DJ-1-like proteins in eukaryotic development

Self-Adapting Resource Escalation for Resilient Signal Processing Architectures

To deal with susceptibility to aging and process variation in the deep submicron era, signal processing systems are sought to maintain quality and throughput requirements despite the vulnerabilities of the underlying computational devices. The Priority Using Resource Escalation (PURE) online resiliency approach is developed herein to maintain throughput quality based on the output Peak Signal-to-Noise Ratio (PSNR) or other health metric. PURE is evaluated using an H.263 video encoder and shown to maintain signal processing throughput despite hardware faults. Its performance is compared to two alternative reconfiguration algorithms which prioritize the optimization of the number of reconfiguration occurrences and the fault detection latency, respectively. For a typical benchmark video sequence, PURE is shown to maintain a PSNR baseline near 32dB. Compared to the alternatives, PURE maintains a PSNR within a difference of 4.02dB to 6.67dB from the fault-free baseline by escalating healthy resources to higher-priority signal processing functions. The diagnosability, reconfiguration latency, and resource overhead of each approach is analyzed. The results indicate the benefits of priority-aware resiliency over conventional redundancy in terms of fault-recovery, power consumption, and resource-area requirements

Temperature stress and redox homeostasis: The synergistic network of redox and chaperone system in response to stress in plants

A remarkable number of strategies has been developed by living organisms to mitigate conflict with environmental changes. The global environment rising with ambient temperature has a wide range of effects on plant growth, and therefore activation of various molecular defenses before the appearance of heat damage. Evidence revealed key components of stress that trigger enhanced tolerance, and some determinants for plant tolerance have been identified. The interplay between heat shock proteins (HSP) and redox proteins is supposed to be vital for the survival under extreme stress conditions. Any circumstance in which cellular redox homeostasis is disrupted can lead to the generation of reactive oxygen species (ROS) that are continuously generated in cells as an unavoidable consequence of aerobic life. Integrative network analysis of synthetic genetic interactions, protein-protein interactions, and functional annotations revealed many new functional processes linked to heat stress (HS) and oxidative stress (OS) tolerance, implicated upstream regulators activated by the either HS or OS, and revealed new connections between them. We present different models of acquired stress resistance to interpret the condition-specific involvement of genes. Considering the basic concepts and the recent advances, the following subsections provide an overview of calcium ion (Ca2+) and ROS interplay in abiotic signaling pathways; further we introduce several examples of chaperone and redox proteins that respond the change of cellular redox status under environmental circumstances. Thus, the involvement or contribution of redox proteins through the functional switching in conjunction with the HSP that prevent heat- and oxidative-induced protein aggregation in plants