Biology subjects

Lee, B.-h.

Publications and source records attributed to Lee, B.-h..

2 recordsLinked to original sources

bioRxiv2026

Loss of Mitochondrial FMT Restores Chloroplast Proteostasis via Inter-organelle Compensation

Chloroplast proteostasis is vital for plant development, yet whether cells can actively reprogram organelle communication to restore plastid function when essential protease components fail remains unclear. Using a forward genetic suppressor screen in Arabidopsis, we identify loss of the mitochondria-associated protein FRIENDLY MITOCHONDRIA (FMT) as a strong suppressor of the virescent and growth-retarded clpc1 mutant, which lacks the major chloroplast Clp chaperone ClpC1. Suppression is highly specific and occurs independently of GUN1-mediated retrograde signaling. Integrated multi-omics analyses reveal that clpc1 and fmtclpc1 represent two distinct organelle signaling states. In clpc1, loss of ClpC1 triggers a plastid stress state characterized by repression of photosynthesis-associated transcription factors, induction of plastid metabolic stress markers, and impaired proteolytic activity. By contrast, loss of FMT shifts the system into a recovery state despite persistent mitochondrial clustering. Mechanistically, FMT negatively regulates CLPC2, a ClpC1 paralog, and fmt-mediated rescue results from CLPC2 derepression. Moderately elevated ClpC2 restores in vivo proteolysis, as evidenced by recovery of PAA2 substrate turnover, normalization of chloroplast ultrastructure, and reactivation of photosynthesis-related gene expression. Transcriptomic and proteomic profiling further reveal coordinated remodeling of nuclear gene expression and chloroplast protein investment in the recovery state, including reduced cytosolic folding stress and selective induction of jasmonic acid- and salicylic acid-associated signaling networks. Genetic analyses establish that REC1 and REC2 are required for full CLPC2 induction and phenotypic recovery. Together, our findings uncover a latent inter-organelle compensatory mechanism in which mitochondrial perturbation reprograms nuclear gene expression to restore chloroplast proteostasis when ClpC1 function is compromised.

plant biology↗

bioRxiv2026

The STA1-DOT2 interaction promotes nuclear speckle formation and splicing robustness in growth and heat stress responses

Pre-mRNA splicing is carried out by the spliceosome, a large and dynamic ribonucleoprotein complex. The spliceosome is known to be stored in nuclear speckles (NS), which are now recognized as active subnuclear organelles for splicing. However, it remains poorly understood how spliceosomal protein-protein interactions are functionally coupled to NS organization to maintain splicing robustness in plants. Here, we report the functional significance of a specific interaction between two U4/U6{middle dot}U5 tri-snRNP components of the spliceosome, STA1 and DOT2, in regulating NS organization, pre-mRNA splicing, and heat stress responses in Arabidopsis. We identified a missense mutation in DOT2 (a Snu66/SART1 homolog) from a genetic suppressor of the PRP6 homolog mutant sta1-1 (named S307). This mutation restored the weakened interaction between STA1 and DOT2 in the sta1-1 mutant background. Genetic, biochemical, and cell biological analyses showed that variation in the strength of the STA1-DOT2 interaction was closely associated with changes in NS formation, splicing efficiency, as well as growth and heat tolerance. Pharmacological inhibition of STA1-associated NS formation by tubercidin recapitulated sta1-1-like phenotypes and splicing defects, supporting a functional link between NS organization and splicing outcomes. In addition, heat-induced weakening of the STA1-DOT2 interaction was accompanied by reduced NS formation and increased intron retention at the transcriptome-wide level including key heat-responsive transcripts. Based on these observations, we propose that the STA1-DOT2 interaction, likely reflecting the assembly state of the U4/U6{middle dot}U5 tri-snRNP, functions as a heat-sensitive interaction node that couples spliceosome assembly to NS organization and splicing robustness under stress conditions.

plant biology↗