Speakers - 2026

Title: Functional insights into the arabidopsis mitochondrial lncRNA NCO

Abstract

Long non-coding RNAs (lncRNAs) are emerging regulators of diverse cellular processes; however, their functions in plant mitochondria remain largely unexplored. In this study, we investigate the role of a 500-nt mitochondrial lncRNA  in Arabidopis thaliana designated as NCO (Non-Coding Overexpressed). While NCO maintains low abundance in wild-type plants, it hyper-accumulates in mitoribosomal mutants likely due to impaired PNPase-mediated degradation. To assess the biological significance of NCO, we utilized mitoTALEN technology to generate two independent Arabidopsis knockout lines lacking this transcript (nco1 and nco3). These lines share an identical upstream deletion breakpoint but differ downstream, resulting in genomic deletions of 1,181 bp and 990 bp, respectively. Here, we present a comparative analysis of respiratory function and stress responses of the nco1 and nco3 mutants to gain insight into the physiological role of  mitochondrial lncRNA. Under standard growth conditions, NCO deficiency only marginally alters Arabidopsis development. Although NCO expression is upregulated approximately 2.5-fold by moderate heat, drought, and salt stress, nco mutants exhibit no increased phenotypic sensitivity to salinity in root growth assay. Respiratory function was analyzed in mitochondria isolated from two-week-old nco1, nco3, and wild-type (wt) seedlings grown in liquid culture. Oxygen consumption measurements revealed a modest but statistically significant decrease in respiratory activity in mitochondria from both NCO-deficient lines compared with wt mitochondria. This reduction was observed with different respiratory substrates, which supply electrons to the mitochondrial respiratory chain through distinct dehydrogenases. Further analysis indicated decreased activity of the cytochrome pathway, associated with reduced activities of complex III and complex IV (cytochrome c oxidase). In contrast, alternative oxidase (AOX) activity was increased in mitochondria from both nco mutants compared with wt. Together, these findings indicate that loss of NCO is associated with remodeling of the mitochondrial respiratory system, characterized by impaired electron transport through the cytochrome pathway and enhanced engagement of the alternative respiratory pathway. The similar respiratory phenotypes of the two independent nco lines support an association between the absence of NCO and altered mitochondrial bioenergetics.

These results provide initial functional evidence linking a plant mitochondrial lncRNA to the regulation or maintenance of respiratory chain function and suggest that NCO may contribute to mitochondrial respiratory homeostasis in Arabidopsis. This work was supported by Grant OPUS-21 (2021/41/B/NZ3/00571) from the National Science Centre, Poland for HJ. This poster presents one of the first functional analyses of a plant mitochondrial long non-coding RNA, providing evidence that NCO contributes to respiratory chain function and mitochondrial homeostasis in Arabidopsis. Attendees will gain new insights into plant mitochondrial lncRNA biology, explore approaches for studying organellar gene regulation and bioenergetics, and learn about the strengths and limitations of mitoTALEN-mediated mitochondrial genome editing. The study provides a foundation for future research on mitochondrial lncRNAs and their roles in plant physiology.