Taoka, H. | bioRxiv Science

bioRxiv2024

Transcriptional Dynamics Uncover the Role of BNIP3 in Mitophagy during Muscle Remodeling in Drosophila

Differentiated muscle cells contain myofibrils and well-organized organelles, enabling powerful contractions. Muscle cell reorganization occurs in response to various physiological stimuli; however, the mechanisms behind this remodeling remain enigmatic due to the lack of a genetically trackable system. Previously, we reported that a subset of larval muscle cells is remodeled into adult abdominal muscle through an autophagy-dependent mechanism in Drosophila. To unveil the underlying mechanisms of this remodeling, we performed a comparative time-course RNA-seq analysis of isolated muscle cells with or without autophagy. It revealed both transcriptional dynamics independent of autophagy and highlighted the significance of BNIP3-mediated mitophagy in muscle remodeling. Mechanistically, we found that BNIP3 recruits autophagic machinery to mitochondria through its LC3-interacting (LIR) motif and minimal essential region (MER), which interact with Atg8a and Atg18a, respectively. Loss of BNIP3 leads to a substantial accumulation of larval mitochondria, ultimately impairing muscle remodeling. In summary, this study demonstrates that BNIP3-dependent mitophagy is critical for orchestrating the dynamic process of muscle remodeling. Impact statementA time-course RNA-seq analysis of muscle remodeling reveals transcriptional dynamics independent of autophagy and highlights the significance of BNIP3 in mitochondrial degradation in vivo.

cell biology↗

bioRxiv2023

The cadmium-hypertolerant fern, Athyrium yokoscense, exhibits two cadmium stress mitigation strategies in the roots and the aerial parts

Athyrium yokoscense is hypertolerant to cadmium (Cd) and can grow normally under a high Cd concentration despite Cd being a highly toxic heavy metal. To mitigate Cd stress in general plant species, Cd is promptly chelated with a thiol compound and is isolated into vacuoles. Generated active oxygen species (ROS) in the cytoplasm are removed by reduced glutathione. However, we found many differences in the countermeasures in A. yokoscense. Thiol compounds accumulated in the stele of the roots, although a long-term Cd exposure induced Cd accumulation in the aerial parts. Synchrotron radiation-based X-ray fluorescence (SR-XRF) analysis indicated that a large amount of Cd was localized in the cell walls of the roots. Overexpression of AyNramp5a, encoding a representative Fe and Mn transporter of A. yokoscense, increased both Cd uptake and iron and manganese uptake in rice calli under the Cd exposure conditions. Organic acids were abundantly detected in A. yokoscense roots. Investigating the chemical forms of the Cd molecules by X-ray absorption fine structure (XAFS) analysis detected many compounds with Cd-oxygen (Cd-O) binding in A. yokoscense roots, whereas in the aerial parts, the ratio of the compounds with Cd-sulfur (Cd-S) binding was increased. Together, our results imply that the strong Cd tolerance of A. yokoscense is an attribute of the following two mechanisms: Cd-O compound formation in the cell wall is a barrier to reduce Cd uptake into aerial parts. Thiol compounds in the region of root stele are involved in detoxication of Cd by formation of Cd-S compounds. Statements and DeclarationsNo potential conflict of interest was reported by the authors.

plant biology↗