The domestic Bactrian camels were treated as one of the principal means of locomotion between the eastern and western cultures in history. However, whether they originated from East Asia or Central Asia remains elusive. To address this question, we perform wholegenome sequencing of 128 camels across Asia. The extant wild and domestic Bactrian camels show remarkable genetic divergence, as they were split from dromedaries. The wild Bactrian camels also contribute little to the ancestry of domestic ones, although they share close habitat in East Asia. Interestingly, among the domestic Bactrian camels, those from Iran exhibit the largest genetic distance and the earliest split from all others in the phylogeny, despite evident admixture between domestic Bactrian camels and dromedaries living in Central Asia. Taken together, our study support the Central Asian origin of domestic Bactrian camels, which were then immigrated eastward to Mongolia where native wild Bactrian camels inhabit.
Autophagy is a conserved pathway for bulk degradation of cytoplasmic material by a double-membrane structure named the autophagosome. The initiation of autophagosome formation requires the recruitment of autophagy-related protein 9 (ATG9) vesicles to the preautophagosomal structure. However, the functional relationship between ATG9 vesicles and the phagophore is controversial in different systems, and the molecular function of ATG9 remains unknown in plants. Here, we demonstrate that ATG9 is essential for endoplasmic reticulum (ER)-derived autophagosome formation in plants. Through a combination of genetic, in vivo imaging and electron tomography approaches, we show that Arabidopsis ATG9 deficiency leads to a drastic accumulation of autophagosome-related tubular structures in direct membrane continuity with the ER upon autophagic induction. Dynamic analyses demonstrate a transient membrane association between ATG9 vesicles and the autophagosomal membrane during autophagy. Furthermore, trafficking of ATG18a is compromised in atg9 mutants during autophagy by forming extended tubules in a phosphatidylinositol 3-phosphatedependent manner. Taken together, this study provides evidence for a pivotal role of ATG9 in regulating autophagosome progression from the ER membrane in Arabidopsis.O ne long-lasting question regarding autophagosome biogenesis is its membrane origin (1). The initiation site for autophagosomes is termed the preautophagosomal structure or phagophore assembly site (PAS). However, the source of the phagophore membrane remains controversial in different systems, and exactly how the phagophore is initiated from its membrane origin is still unclear. The core autophagy-related (ATG) machinery regulates phagophore assembly in a spatiotemporally coordinated manner whereas some of the ATG components will disassociate from the completed autophagosome and some are turned over together with the autophagosome (1-3).As the sole transmembrane protein, autophagy-related protein 9 (ATG9) has long been suggested to provide a lipid/membrane source for autophagosome formation because ATG9-deficient mutants in yeast or mammal fail to form autophagosomes (4, 5). Although ATG9 is conserved in all eukaryotes (6), it seems that ATG9 might perform its function divergently in different systems. In yeast, ATG9 participates in an early step by shuttling from a non-PAS site to the PAS site and supports an assembly model for yeast autophagosome biogenesis (4). In contrast, mammalian ATG9 is not stably incorporated into the isolation membrane or autophagosomes but is instead transiently associated with the omegasome, a phosphatidylinositol 3-phosphate (PI3P)-enriched endoplasmic reticulum (ER) subdomain (5). Cryomicroscopy studies have shown a close association between ATG9 vesicles and the omegasome structure (7), together with the presence of ATG9 on tubulovesicular membranes surrounding autophagosomes (5). A recent finding by livecell imaging indicates that autophagosome formation occurs where ATG9 vesicles coalesce with the ER ...
Protein secretion is an essential process in all eukaryotic cells and its mechanisms have been extensively studied. Proteins with an N-terminal leading sequence or transmembrane domain are delivered through the conventional protein secretion (CPS) pathway from the endoplasmic reticulum (ER) to the Golgi apparatus. This feature is conserved in yeast, animals, and plants. In contrast, the transport of leaderless secretory proteins (LSPs) from the cytosol to the cell exterior is accomplished via the unconventional protein secretion (UPS) pathway. So far, the CPS pathway has been well characterized in plants, with several recent studies providing new information about the regulatory mechanisms involved. On the other hand, studies on UPS pathways in plants remain descriptive, although a connection between UPS and the plant defense response is becoming more and more apparent. In this review, we present an update on CPS and UPS. With the emergence of new techniques, a more comprehensive understanding of protein secretion in plants can be expected in the future.
Cell cycle progression from G 1 to S phase depends on phosphorylation of pRb by complexes containing a cyclin (D type or E type) and cyclin-dependent kinase (e.g., cdk2, cdk4, or cdk6). Ink4 proteins function to oppose the action of cdk4/ 6-cyclin D complexes by inhibiting cdk4/6. We employed genetic and pharmacologic approaches to study the interplay among Ink4 proteins and cdk4/6 activity in vivo. Mouse embryo fibroblasts (MEF) lacking p16Ink4a and p18Ink4c
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