A peroxiredoxin-P38 MAPK scaffold increases MAPK activity by MAP3K-independent mechanisms.

Peroxiredoxins (Prdxs) utilize reversibly oxidized cysteine residues to reduce peroxides and promote H2O2 signal transduction, including H2O2-induced activation of P38 MAPK. Prdxs form H2O2-induced disulfide complexes with many proteins, including multiple kinases involved in P38 MAPK signaling. Here, we show that a genetically encoded fusion between a Prdx and P38 MAPK is sufficient to hyperactivate the kinase in yeast and human cells by a mechanism that does not require the H2O2-sensing cysteine of the Prdx. We demonstrate that a P38-Prdx fusion protein compensates for loss of the yeast scaffold protein Mcs4 and MAP3K activity, driving yeast into mitosis. Based on our findings, we propose that the H2O2-induced formation of Prdx-MAPK disulfide complexes provides an alternative scaffold and signaling platform for MAPKK-MAPK signaling. The demonstration that formation of a complex with a Prdx is sufficient to modify the activity of a kinase has broad implications for peroxide-based signal transduction in eukaryotes.

Detection of Beet curly top virus in Solanum jamesii, Artemisia tridentata, Helianthus annuus, and Cannabis sativa in Utah.

Historically, beet curly top virus (BCTV; Geminiviridae, Curtovirus) is known for destroying the sugar beet industry in Utah and has been a persistent problem in the state since then (Ball, 1917). Starting in June of 2022, we began identifying plants in San Juan County, Utah with chlorosis and leaf curling. Of note, Solanum jamesii, the Four Corners potato, Artemisia tridentata, big sagebrush, and Helianthus annuus, common sunflower, were found with general chlorosis, severe leaf curling and in the case of the sage brush, completely lacking in smell whereas nearby sage plants without the yellowing were intensely fragrant. In August 2023, Cannabis sativa plants for hemp production were found with severe leaf curling in Juab County, Utah. Samples were collected and stored at -80°C for future work. DNA was extracted using the IBI Genomic Plant DNA kit (IBI Scientific, Dubuque, IA) and subjected to rolling circle amplification using Phi29 polymerase (NEB, Ipswich, MA). The primer set BCTV2 (Strausbaugh et al. 2008) for BCTV detection was then used on a subset of the RCA-positive samples for either one (A. tridentata, H. annus, and S. jamesii) or two (C. sativa) plants displaying classic BCTV symptoms, to amplify a 518 bp region. This amplicon was then sequenced by the Sanger method to a 4x coverage. The resulting sequences (accession nos. OR698900 to OR698904) share 98.94 to 99.80% nucleotide identity to the Worland strain (accession no. KU892789.1) for all samples. To confirm the detection, a triple antibody sandwich ELISA kit from Nano Diagnostics (San Jose, CA) was used on these, and other plants of similar species and symptoms from across the state. Samples that tested positive include 3/3 symptomatic H. annuus plants, 1/1 symptomatic S. jamesii, 3/3 symptomatic A. tridentata. The A. tridentata samples were collected from Juab, San Juan, and Utah Counties. None of three asymptomatic A. tridentata plants tested were ELISA positive. Of the C. sativa plants tested by ELISA, 9/9 of the plants displaying classic BCTV symptoms in that host were positive and 6/6 of the plants without classic BCTV symptoms were ELISA positive. The findings of these novel hosts indicate the need for increased testing and analysis of economically relevant crops and native flora across the state. These findings represent a concern for conservation in the case of S. jamesii and a potential threat to the growing hemp industry in the state due to the severity of BCTV symptoms on these plants. Additionally, the finding of A. tridentata as a host may represent a significant finding for the epidemiology of BCTV in the Mountain West region as A. tridentata is distributed from Mexico to Canada along the Rocky Mountain range and is found in much of the Western US in arid regions. This is the first report, to our knowledge, of S. jamesii and A. tridentata as hosts for BCTV and the first peer reviewed reports for H. annuus and C. sativa as hosts for BCTV in Utah.