Involvement of OsPht1;4 in phosphate acquisition and mobilization facilitates embryo development in rice

Phosphate (Pi) transporters mediate acquisition and transportation of Pi within plants. Here, we investigated the functions of OsPht1;4 (OsPT4), one of the 13 members of the Pht1 family in rice. Quantitative real‐time RT‐PCR analysis revealed strong expression of OsPT4 in roots and embryos, and OsPT4 promoter analysis using reporter genes confirmed these findings. Analysis using rice protoplasts showed that OsPT4 localized to the plasma membrane. OsPT4 complemented a yeast mutant defective in Pi uptake, and also facilitated increased accumulation of Pi in Xenopus oocytes. Further, OsPT4 genetically modified (GM) rice lines were generated by knockout/knockdown or over‐expression of OsPT4. Pi concentrations in roots and shoots were significantly lower and higher in knockout/knockdown and over‐expressing plants, respectively, compared to wild‐type under various Pi regimes. ³³Pi uptake translocation assays corroborated the altered acquisition and mobilization of Pi in OsPT4 GM plants. We also observed effects of altered expression levels of OsPT4 in GM plants on the concentration of Pi, the size of the embryo, and several attributes related to seed development. Overall, our results suggest that OsPT4 encodes a plasma membrane‐localized Pi transporter that facilitates acquisition and mobilization of Pi, and also plays an important role in development of the embryo in rice.     

Binding cavities and druggability of intrinsically disordered proteins

To assess the potential of intrinsically disordered proteins (IDPs) as drug design targets, we have analyzed the ligand-binding cavities of two datasets of IDPs (containing 37 and 16 entries, respectively) and compared their properties with those of conventional ordered (folded) proteins. IDPs were predicted to possess more binding cavity than ordered proteins at similar length, supporting the proposed advantage of IDPs economizing genome and protein resources. The cavity number has a wide distribution within each conformation ensemble for IDPs. The geometries of the cavities of IDPs differ from the cavities of ordered proteins, for example, the cavities of IDPs have larger surface areas and volumes, and are more likely to be composed of a single segment. The druggability of the cavities was examined, and the average druggable probability is estimated to be 9% for IDPs, which is almost twice that for ordered proteins (5%). Some IDPs with druggable cavities that are associated with diseases are listed. The optimism versus obstacles for drug design for IDPs is also briefly discussed.     

Ci antagonizes Hippo signaling in the somatic cells of the ovary to drive germline stem cell differentiation

Many stem cell populations are tightly regulated by their local microenvironment (niche), which comprises distinct types of stromal cells. However, little is known about mechanisms by which niche subgroups coordinately determine the stem cell fate. Here we identify that Yki, the key Hippo pathway component, is essential for escort cell (EC) function in promoting germline differentiation in Drosophila ovary. We found that Hedgehog (Hh) signals emanating primarily from cap cells support the function of ECs, where Cubitus interruptus (Ci), the Hh signaling effector, acts to inhibit Hippo kinase cascade activity. Mechanistically, we found that Ci competitively interacts with Hpo and impairs the Hpo-Wts signaling complex formation, thereby promoting Yki nuclear localization. The actions of Ci ensure effective Yki signaling to antagonize Sd/Tgi/Vg-mediated default repression in ECs. This study uncovers a mechanism explaining how subgroups of niche cells coordinate to determine the stem cell fate via Hh-Hippo signaling crosstalk, and enhances our understanding of mechanistic regulations of the oncogenic Yki/YAP signaling.     

Three-dimensional human facial morphologies as robust aging markers

Aging is associated with many complex diseases. Reliable prediction of the aging process is important for assessing the risks of aging-associated diseases. However, despite intense research, so far there is no reliable aging marker. Here we addressed this problem by examining whether human 3D facial imaging features could be used as reliable aging markers. We collected > 300 3D human facial images and blood profiles well-distributed across ages of 17 to 77 years. By analyzing the morphological profiles, we generated the first comprehensive map of the aging human facial phenome. We identified quantitative facial features, such as eye slopes, highly associated with age. We constructed a robust age predictor and found that on average people of the same chronological age differ by ± 6 years in facial age, with the deviations increasing after age 40. Using this predictor, we identified slow and fast agers that are significantly supported by levels of health indicators. Despite a close relationship between facial morphological features and health indicators in the blood, facial features are more reliable aging biomarkers than blood profiles and can better reflect the general health status than chronological age.     

The Streptomyces coelicolor Lipoate-protein Ligase Is a Circularly Permuted Version of the Escherichia coli Enzyme Composed of Discrete Interacting Domains

Lipoate-protein ligases are used to scavenge lipoic acid from the environment and attach the coenzyme to its cognate proteins, which are generally the E2 components of the 2-oxoacid dehydrogenases. The enzymes use ATP to activate lipoate to its adenylate, lipoyl-AMP, which remains tightly bound in the active site. This mixed anhydride is attacked by the ϵ-amino group of a specific lysine present on a highly conserved acceptor protein domain, resulting in the amide-linked coenzyme. The Streptomyces coelicolor genome encodes only a single putative lipoate ligase. However, this protein had only low sequence identity (<25%) to the lipoate ligases of demonstrated activity and appears to be a circularly permuted version of the known lipoate ligase proteins in that the canonical C-terminal domain seems to have been transposed to the N terminus. We tested the activity of this protein both by in vivo complementation of an Escherichia coli ligase-deficient strain and by in vitro assays. Moreover, when the domains were rearranged into a protein that mimicked the arrangement found in the canonical lipoate ligases, the enzyme retained complementation activity. Finally, when the two domains were separated into two proteins, both domain-containing proteins were required for complementation and catalysis of the overall ligase reaction in vitro. However, only the large domain-containing protein was required for transfer of lipoate from the lipoyl-AMP intermediate to the acceptor proteins, whereas both domain-containing proteins were required to form lipoyl-AMP.     

Calcium release through P2X4 activates calmodulin to promote endolysosomal membrane fusion

Intra-endolysosomal Ca²⁺ release is required for endolysosomal membrane fusion with intracellular organelles. However, the molecular mechanisms for intra-endolysosomal Ca²⁺ release and the downstream Ca²⁺ targets involved in the fusion remain elusive. Previously, we demonstrated that endolysosomal P2X4 forms channels activated by luminal adenosine triphosphate in a pH-dependent manner. In this paper, we show that overexpression of P2X4, as well as increasing endolysosomal P2X4 activity by alkalinization of endolysosome lumen, promoted vacuole enlargement in cells and endolysosome fusion in a cell-free assay. These effects were prevented by inhibiting P2X4, expressing a dominant-negative P2X4 mutant, and disrupting the P2X4 gene. We further show that P2X4 and calmodulin (CaM) form a complex at endolysosomal membrane where P2X4 activation recruits CaM to promote fusion and vacuolation in a Ca²⁺-dependent fashion. Moreover, P2X4 activation-triggered fusion and vacuolation were suppressed by inhibiting CaM. Our data thus suggest a new molecular mechanism for endolysosomal membrane fusion involving P2X4-mediated endolysosomal Ca²⁺ release and subsequent CaM activation.