Analysis of the quadruple lsu mutant reveals molecular determinants of the role of LSU proteins in sulfur assimilation in Arabidopsis

• Published in: The Plant journal : for cell and molecular biology 2024-12, Vol.120 (6), p.2919-2936
• Main Authors: Piotrowska, Justyna, Wawrzyńska, Anna, Olszak, Marcin, Krzyszton, Michal, Apodiakou, Anastasia, Alseekh, Saleh, Ramos, José María López, Hoefgen, Rainer, Kopriva, Stanislav, Sirko, Agnieszka
• Format: Article
• Language: English
• Subjects: Adenosine; Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; ATP sulfurylase; Enzymatic activity; Gene Expression Regulation, Plant; Homeostasis; Isoforms; LSU (RESPONSE TO LOW SULFUR); Metabolism; Mutants; Mutation; Nutrients; Original; Oxidoreductases Acting on Sulfur Group Donors - genetics; Oxidoreductases Acting on Sulfur Group Donors - metabolism; Plant layout; Proteins; Reductases; Sulfate Adenylyltransferase - genetics; Sulfate Adenylyltransferase - metabolism; sulfate deficiency; Sulfate reduction; Sulfates; Sulfates - metabolism; Sulfite; Sulfite reductase; Sulfur; Sulfur - metabolism; Transcriptomics
• ISSN: 0960-7412; 1365-313X; 1365-313X
• DOI: 10.1111/tpj.17155

SUMMARY Because plants are immobile, they have developed intricate mechanisms to sense and absorb nutrients, adjusting their growth and development accordingly. Sulfur is an essential macroelement, but our understanding of its metabolism and homeostasis is limited. LSU (RESPONSE TO LOW SULFUR) proteins are plant‐specific proteins with unknown molecular functions and were first identified during transcriptomic studies on sulfur deficiency in Arabidopsis. These proteins are crucial hubs that integrate environmental signals and are involved in the response to various stressors. Herein, we report the direct involvement of LSU proteins in primary sulfur metabolism. Our findings revealed that the quadruple lsu mutant, q‐lsu‐KO, which was grown under nonlimiting sulfate conditions, exhibited a molecular response resembling that of sulfur‐deficient wild‐type plants. This led us to explore the interactions of LSU proteins with sulfate reduction pathway enzymes. We found that all LSU proteins interact with ATPS1 and ATPS3 isoforms of ATP sulfurylase, all three isoforms of adenosine 5´ phosphosulfate reductase (APR), and sulfite reductase (SiR). Additionally, in vitro assays revealed that LSU1 enhances the enzymatic activity of SiR. These results highlight the supportive role of LSU proteins in the sulfate reduction pathway. Significance Statement This study demonstrates that the quadruple lsu mutant exhibits impaired sulfate assimilation and reduction at the transcript, metabolite, and long‐distance sulfur flux levels. Our subsequent research has revealed the molecular mechanism underlying these findings, showing a direct interaction between LSU proteins and enzymes involved in sulfate reduction, particularly sulfite reductase (SiR), with LSU1 enhancing SiR activity.