Speakers - 2026

Title: Functional Analysis of Mitochondrial Long Non Coding RNA NCO in Arabidopsis

Abstract

Long non coding RNAs are emerging regulators of diverse cellular processes, but their functions in plant mitochondria remain largely unexplored. This study investigates the role of a 500 nucleotide mitochondrial long non coding RNA in Arabidopsis thaliana designated NCO or Non Coding Overexpressed. NCO maintains low abundance in wild type plants but accumulates in mitoribosomal mutants, likely due to impaired PNPase mediated degradation. Using mitoTALEN technology, two independent Arabidopsis knockout lines, nco1 and nco3, were generated. Comparative analysis of respiratory function and stress responses revealed that NCO deficiency only marginally affects plant development under standard conditions. Although NCO expression increases under moderate heat, drought, and salt stress, the mutant lines showed no increased sensitivity to salinity in root growth assays. Oxygen consumption measurements revealed a modest but statistically significant reduction in respiratory activity in mitochondria from both NCO deficient lines compared with wild type plants. Reduced activity of the cytochrome pathway was associated with decreased activities of complex III and complex IV, while alternative oxidase activity increased in both mutant lines. These findings indicate that loss of NCO is associated with remodeling of the mitochondrial respiratory system, characterized by impaired cytochrome pathway activity and enhanced alternative respiration. The similar respiratory phenotypes of the two independent mutant lines support an association between NCO deficiency and altered mitochondrial bioenergetics. This study provides initial functional evidence linking a plant mitochondrial long non coding RNA with respiratory chain function and mitochondrial homeostasis in Arabidopsis.