Abscisic acid-controlled redox proteome of Arabidopsis and its regulation by heterotrimeric Gß protein.

The plant hormone abscisic acid (ABA) plays crucial roles in regulation of stress responses and growth modulation. Heterotrimeric G-proteins are key mediators of ABA responses. Both ABA and G-proteins have also been implicated in intracellular redox regulation; however, the extent to which reversible protein oxidation manipulates ABA and/or G-protein signaling remains uncharacterized. To probe the role of reversible protein oxidation in plant stress response and its dependence on G-proteins, we determined the ABA-dependent reversible redoxome of wild-type and Gß-protein null mutant agb1 of Arabidopsis. We quantified 6891 uniquely oxidized cysteine-containing peptides, 923 of which show significant changes in oxidation following ABA treatment. The majority of these changes required the presence of G-proteins. Divergent pathways including primary metabolism, reactive oxygen species response, translation and photosynthesis exhibited both ABA- and G-protein-dependent redox changes, many of which occurred on proteins not previously linked to them. We report the most comprehensive ABA-dependent plant redoxome and uncover a complex network of reversible oxidations that allow ABA and G-proteins to rapidly adjust cellular signaling to adapt to changing environments. Physiological validation of a subset of these observations suggests that functional G-proteins are required to maintain intracellular redox homeostasis and fully execute plant stress responses.

SARS-CoV-2 mutations: the biological trackway towards viral fitness.

The outbreak of pneumonia-like respiratory disorder at China and its rapid transmission world-wide resulted in public health emergency, which brought lineage B betacoronaviridae SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) into spotlight. The fairly high mutation rate, frequent recombination and interspecies transmission in betacoronaviridae are largely responsible for their temporal changes in infectivity and virulence. Investigation of global SARS-CoV-2 genotypes revealed considerable mutations in structural, non-structural, accessory proteins as well as untranslated regions. Among the various types of mutations, single-nucleotide substitutions are the predominant ones. In addition, insertion, deletion and frame-shift mutations are also reported, albeit at a lower frequency. Among the structural proteins, spike glycoprotein and nucleocapsid phosphoprotein accumulated a larger number of mutations whereas envelope and membrane proteins are mostly conserved. Spike protein and RNA-dependent RNA polymerase variants, D614G and P323L in combination became dominant world-wide. Divergent genetic variants created serious challenge towards the development of therapeutics and vaccines. This review will consolidate mutations in different SARS-CoV-2 proteins and their implications on viral fitness.

The TARANI/ UBIQUITIN PROTEASE 14 protein is required for lateral root development in Arabidopsis.

In our article published in Plant Physiology, we had reported tarani (tni) mutant in Arabidopsis, in which poly-ubiquitin hydrolysis is adversely affected, shows pleiotropic phenotypic defects including fewer lateral roots due to the stabilization of several AUX/IAAs and reduced auxin response. TNI encodes UBIQUITIN-SPECIFIC PROTEASE14 that maintains normal auxin response through ubiquitin recycling. Fewer lateral roots observed in tni could be due to defects in their primordia initiation or subsequent elongation post-initiation. Here we have tested this by marking the lateral root primordia with pCycB1;1::CycB1;1(DB):GUS reporter and counting the number of lateral root at various stages development of as a marker of lateral root primordium. The results suggest that TNI/UBP14 is required for LRP development, and a reduction in TNI activity causes a delay in LRP initiation and consequently shorter lateral roots in the tni seedlings. ABBREVIATIONS: LRP, lateral root primordium; XPP, xylem pole pericycle; LRFC, lateral root founder cells.

ORF3a mutation associated with higher mortality rate in SARS-CoV-2 infection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has recently caused acute respiratory distress syndrome affecting more than 200 countries with varied mortality rate. Successive genetic variants of SARS-CoV-2 become evident across the globe immediately after its complete genome sequencing. Here, we found a decent association of SARS-CoV-2 ORF3a mutation with higher mortality rate. Extensive in silico studies revealed several amino acid changes in ORF3a protein which ultimately leads to diverse structural modifications like B cell epitope loss, gain/loss of phosphorylation site and loss of leucine zipper motif. We could further relate these changes to the enhanced antigenic diversity of SARS-CoV-2. Through protein−protein network analysis and functional annotation studies, we obtained a close federation of ORF3a protein with host immune response via divergent signal transduction pathways including JAK-STAT, chemokine and cytokine-related pathways. Our data not only unveil the fairly appreciable association of ORF3a mutation with higher mortality rate, but also suggest a potential mechanistic insight towards the immunopathogenic manifestation of SARS-CoV-2 infection.

The Ubiquitin-Specific Protease TNI/UBP14 Functions in Ubiquitin Recycling and Affects Auxin Response.

The ubiquitin-mediated proteasomal pathway regulates diverse cellular processes in plants by rapidly degrading target proteins, including the repressors of hormone signaling. Though ubiquitin proteases play a key role in this process by cleaving polyubiquitin chains to monomers, their function has not been studied in detail by mutational analysis. Here, we show that mutation in TARANI/UBIQUITIN-SPECIFIC PROTEASE14 (TNI/UBP14) leads to reduced auxin response and widespread auxin-related phenotypic defects in Arabidopsis (Arabidopsis thaliana). In a tni partial loss-of-function mutant that was originally isolated based on altered leaf shape, activity of the auxin-responsive reporters DR5::GUS, DR5::nYFP, and IAA2::GUS was reduced. Genetic interaction studies suggest that TNI is involved in auxin signaling and acts alongside TIR1, ARF7, and AUX1 Map-based cloning identified TNI as UBP14 Inefficient splicing of the mutant TNI transcript resulted in the formation of an inactive UBP14 protein, which led to accumulation of polyubiquitin chains and excess polyubiquitinated proteins in the mutant. In addition to the reduced auxin response, increased levels of DII:VENUS, IAA18:GUS, and HS::AXR3-NT:GUS were also observed in tni, perhaps due to inefficient polyubiquitin hydrolysis and proteasome-mediated degradation. Together, our study identifies a function for TNI/UBP14 in the auxin response through ubiquitin recycling.