Pathways of ROS homeostasis regulation in "Mesembryanthemum crystallinum" L. calli exhibiting differences in rhizogenesis

A comparison of the hydrogen peroxide (H2O2) content, proline and betacyanin concentration and activities of some antioxidant enzymes (catalase, superoxide dismutase, guaiacol and ascorbate peroxidases) was made in Mesembryanthemum crystallinum L. calli differing in rhizogenic potential. Callus was induced from hypocotyls of 10-day-old seedlings on a medium containing 1 mg l−1 2,4-dichlorophenoxyacetic acid and 0.2 mg l−1 kinetin, which was either supplemented with 40 mM NaCl (CIM-NaCl medium) or did not contain any salt (CIM medium). The callus obtained on CIM-NaCl was rhizogenic, whereas the callus induced on the medium without salt was non-rhizogenic throughout the culture. The rhizogenic callus differed from the non-rhizogenic callus in lower betacyanin and H2O2 content, but the rhizogenic callus displayed a higher proline level. The activity of H2O2 scavenging enzymes, such as catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (POD), was markedly higher in the rhizogenic callus than in the non-rhizogenic callus, but the total activity of superoxide dismutase (SOD) was higher in the non-rhizogenic callus than in the rhizogenic callus. Aminotriazole (CAT inhibitor) and diethyldithiocarbamate (SOD inhibitor) were added solely to the CIM and CIM-NaCl media to manipulate the concentration of reactive oxygen species (ROS) in the cultured tissues. Both CAT and SOD inhibitors brought about an increase in H2O2 content in calli cultured on CIM-NaCl and the loss of rhizogenic potential. Conversely, the addition of inhibitors to the medium without salt led to a decrease in H2O2 content. This corresponded with a significant decrease in the endogenous concentration of betacyanins, but did not change the lack of rhizogenic ability

A Window into the Early–Middle Stone Age Transition in Northeastern Africa—A Marine Isotope Stage 7a/6 Late Acheulean Horizon from the EDAR 135 Site, Eastern Sahara (Sudan)

This paper presents the results of the analysis of a late Acheulean horizon from the EDAR 135 site, which was discovered in the Eastern Desert, Sudan, in an area heavily transformed by modern mining activity. A lithic assemblage was discovered there, within a layer of gravel sediments formed by a paleostream in a humid period of the Middle Pleistocene. This layer is OSL dated between 220 ± 12 and 145 ± 20 ka (MIS 7a/6). These dates indicate that the assemblage could be the youngest trace of the Acheulean in northeastern Africa. Technological analysis of the lithics reveals different core reduction strategies, including not only ad hoc ones based on multiplatform cores, but also discoidal and prepared cores. The use of prepared core reduction methods has already been confirmed at other Late Acheulean sites in Africa and the Middle East. Microwear traces observed on lithic artifacts could relate to on-site butchering activities

A Mismatched Piece in a Cultural Middle Stone Age Puzzle: Traces of Human Activity Dated to 90 kya (MIS 5) at Sites EDAR 134 and 155 in the Eastern Sahara, Sudan

This article presents the results of research carried out at two previously unreported Eastern Desert Atbara River project (EDAR) Middle Stone Age (MSA) sites—EDAR 134 and EDAR 155. Luminescence dating results indicate human activity in this area during the Marine Isotope Stage 5 period (MIS 5), approximately 90 kya. Discussion concerning the affiliation of both analyzed inventories will be provided, including another MSA site from the EDAR area, where an assemblage dated to MIS 6/5e does not have technological features known from other technocomplexes in the eastern Sahara region (EDAR 135). Microscopic analysis of traces of tool use for the EDAR 155 assemblage shows the high impact of post-depositional (aeolian) processes on the state of preservation of lithic material. Sites EDAR 134 and 155 provide evidence for hominin activity during the late Pleistocene within an area only episodically accessible, due to arid conditions prevailing in the Saharan deserts

Phosphorylation of P-stalk proteins defines the ribosomal state for interaction with auxiliary protein factors

Ribosomal action is facilitated by the orchestrated work of trans-acting factors and ribosomal elements, which are subject to regulatory events, often involving phosphorylation. One such element is the ribosomal P-stalk, which plays a dual function: it activates translational GTPases, which support basic ribosomal functions, and interacts with the Gcn2 kinase, linking the ribosomes to the ISR pathway. We show that P-stalk proteins, which form a pentamer, exist in the cell exclusively in a phosphorylated state at five C-terminal domains (CTDs), ensuring optimal translation (speed and accuracy) and may play a role in the timely regulation of the Gcn2-dependent stress response. Phosphorylation of the CTD induces a structural transition from a collapsed to a coil-like structure, and the CTD gains conformational freedom, allowing specific but transient binding to various protein partners, optimizing the ribosome action. The report reveals a unique feature of the P-stalk proteins, indicating that, unlike most ribosomal proteins, which are regulated by phosphorylation in an on/off manner, the P-stalk proteins exist in a constantly phosphorylated state, which optimizes their interaction with auxiliary factors