Osteoclasts（OCs）seeded on bone slices either drill round pits or dig long trenches.Whereas pits correspond to intermittent resorption,trenches correspond to continuous and faster resorption and require a distinct as...Osteoclasts（OCs）seeded on bone slices either drill round pits or dig long trenches.Whereas pits correspond to intermittent resorption,trenches correspond to continuous and faster resorption and require a distinct assembly of the resorption apparatus.It is unknown whether the distinction between pits and trenches has any biological relevance.Using OCs prepared from different blood donors,we found that female OCs achieved increased resorption mainly through pit formation,whereas male OCs did so through trench formation.Trench formation went along with high collagenolytic activity and high cathepsin K（CatK）expression,thereby allowing deeper demineralization.A specific CatK inhibitor abrogated the generation of trenches,while still allowing the generation of pits.OCs obtained from bone marrow were more prone to generate trenches than those obtained from blood.Scanning electron microscopy of bone surfaces eroded in vivo showed trenches and pits of similar size as those made by OCs in culture.We conclude that the distinction between trench-and pit-forming OCs is relevant to the differences among OCs from different skeletal sites,different individuals,including gender,and results from differences in colIagenolytic power.This indicates a biological relevance and highlights the importance of discriminating between pits and trenches when assessing resorption.展开更多
Coordinated gene transcription in plastids and nuclei is necessary for the photosynthetic apparatus assembly during chloroplast biogenesis. Despite the identification of several transcription factors regulating nuclea...Coordinated gene transcription in plastids and nuclei is necessary for the photosynthetic apparatus assembly during chloroplast biogenesis. Despite the identification of several transcription factors regulating nuclear-encoded photosynthetic gene transcription, transcription factors regulating plastid gene transcription are barely reported. Here, we report that BAI1 (“albino” in Chinese), a nucleus–plastid dual-targeted C2H2-type zinc-finger transcription factor in Arabidopsis, positively regulates and tunes the transcription of both nuclear and plastid genes. Knockout of BAI1 blocks chloroplast formation, producing albino seedlings and lethality. In plastids, BAI1 is a newly identified functional component of the pTAC (transcriptionally active chromosome complex), which interacts with another pTAC component, pTAC12/PAP5/HMR, to allow the effective assembly of plastid-encoded RNA polymerase (PEP) complexes. The transcript levels of PEP-dependent genes were reduced in the bai1 mutant. In contrast, the accumulation of nuclear-encoded RNA polymerase (NEP)-dependent transcripts was increased, suggesting that BAI1 is critical in maintaining PEP activity. BAI1 directly binds to the promoter regions of nuclear genes RbcSs and a plastid gene RbcL to activate their expression for RubisCO assembly. AtBAI1 homologs TaBAI1, GmBAI1a, and GmBAI1b from monocots and dicots can fully complement the defects of the Arabidopsis bai1 mutant. In contrast, Physcomitrium patens BAI1 (PpBAI1) only partially complements the bai1 mutant. Phylogenetic analysis of BAI1 and HMR uncovered that both components arose from late-diverging streptophyte algae, following a conserved evolutionary path during terrestrialization. In summary, this work unveils a BAI1-mediated transcription regulatory mechanism synchronizing the transcription of nuclear and plastid genes, necessary for hybrid photosynthetic complex assembly. This could be an intrinsic feature facilitating plant terrestrialization.展开更多
基金the project nurse,Jane Schwartz Leonhardt,at the Department of Orthopedic Surgery at Vejle Hospital for her great collaborationfinanced by Vejle Hospital/Lillebaelt Hospital
文摘Osteoclasts（OCs）seeded on bone slices either drill round pits or dig long trenches.Whereas pits correspond to intermittent resorption,trenches correspond to continuous and faster resorption and require a distinct assembly of the resorption apparatus.It is unknown whether the distinction between pits and trenches has any biological relevance.Using OCs prepared from different blood donors,we found that female OCs achieved increased resorption mainly through pit formation,whereas male OCs did so through trench formation.Trench formation went along with high collagenolytic activity and high cathepsin K（CatK）expression,thereby allowing deeper demineralization.A specific CatK inhibitor abrogated the generation of trenches,while still allowing the generation of pits.OCs obtained from bone marrow were more prone to generate trenches than those obtained from blood.Scanning electron microscopy of bone surfaces eroded in vivo showed trenches and pits of similar size as those made by OCs in culture.We conclude that the distinction between trench-and pit-forming OCs is relevant to the differences among OCs from different skeletal sites,different individuals,including gender,and results from differences in colIagenolytic power.This indicates a biological relevance and highlights the importance of discriminating between pits and trenches when assessing resorption.
基金supported by the National Natural Science Foundation of China National Natural Science Foundation of China(32070550 and 31872631).
文摘Coordinated gene transcription in plastids and nuclei is necessary for the photosynthetic apparatus assembly during chloroplast biogenesis. Despite the identification of several transcription factors regulating nuclear-encoded photosynthetic gene transcription, transcription factors regulating plastid gene transcription are barely reported. Here, we report that BAI1 (“albino” in Chinese), a nucleus–plastid dual-targeted C2H2-type zinc-finger transcription factor in Arabidopsis, positively regulates and tunes the transcription of both nuclear and plastid genes. Knockout of BAI1 blocks chloroplast formation, producing albino seedlings and lethality. In plastids, BAI1 is a newly identified functional component of the pTAC (transcriptionally active chromosome complex), which interacts with another pTAC component, pTAC12/PAP5/HMR, to allow the effective assembly of plastid-encoded RNA polymerase (PEP) complexes. The transcript levels of PEP-dependent genes were reduced in the bai1 mutant. In contrast, the accumulation of nuclear-encoded RNA polymerase (NEP)-dependent transcripts was increased, suggesting that BAI1 is critical in maintaining PEP activity. BAI1 directly binds to the promoter regions of nuclear genes RbcSs and a plastid gene RbcL to activate their expression for RubisCO assembly. AtBAI1 homologs TaBAI1, GmBAI1a, and GmBAI1b from monocots and dicots can fully complement the defects of the Arabidopsis bai1 mutant. In contrast, Physcomitrium patens BAI1 (PpBAI1) only partially complements the bai1 mutant. Phylogenetic analysis of BAI1 and HMR uncovered that both components arose from late-diverging streptophyte algae, following a conserved evolutionary path during terrestrialization. In summary, this work unveils a BAI1-mediated transcription regulatory mechanism synchronizing the transcription of nuclear and plastid genes, necessary for hybrid photosynthetic complex assembly. This could be an intrinsic feature facilitating plant terrestrialization.
