The interaction of CaM7 and CNGC14 regulates root hair growth in Arabidopsis

Oscillations in cytosolic free calcium determine the polarity of tip‐growing root hairs. The Ca²⁺ channel cyclic nucleotide gated channel 14 (CNGC14) contributes to the dynamic changes in Ca²⁺ concentration gradient at the root hair tip. However, the mechanisms that regulate CNGC14 are unknown. In this study, we detected a direct interaction between calmodulin 7 (CaM7) and CNGC14 through yeast two‐hybrid and bimolecular fluorescence complementation assays. We demonstrated that the third EF‐hand domain of CaM7 specifically interacts with the cytosolic C‐terminal domain of CNGC14. A two‐electrode voltage clamp assay showed that CaM7 completely inhibits CNGC14‐mediated Ca²⁺ influx, suggesting that CaM7 negatively regulates CNGC14‐mediated calcium signaling. Furthermore, CaM7 overexpressing lines phenocopy the short root hair phenotype of a cngc14 mutant and this phenotype is insensitive to changes in external Ca²⁺ concentrations. We, thus, identified CaM7‐CNGC14 as a novel interacting module that regulates polar growth in root hairs by controlling the tip‐focused Ca²⁺ signal.     

The Sec1/Munc18-like proteins TgSec1 and TgVps45 play pivotal roles in assembly of the pellicle and sub-pellicle network in Toxoplasma gondii

Post-Golgi vesicle trafficking is indispensable for precise movement of proteins to the pellicle, the sub-pellicle network and apical secretory organelles in Apicomplexa. However, only a small number of molecular complexes involved in trafficking, tethering and fusion of vesicles have been identified in Toxoplasma gondii. Consequently, it is unclear how complicated vesicle trafficking is accomplished in this parasite. Sec1/Munc18-like (SM) proteins are essential components of protein complexes involved in vesicle fusion. Here, we found that depletion of the SM protein TgSec1 using an auxin-inducible degron-based conditional knockout strategy led to mislocalization of plasma membrane proteins. By contrast, conditional depletion of the SM protein TgVps45 led to morphological changes, asymmetrical loss of the inner membrane complex and defects in nucleation of sub-pellicular microtubules, polarization and symmetrical assembly of daughter parasites during repeated endodyogeny. TgVps45 interacts with the SNARE protein TgStx16 and TgVAMP4-1. Conditional ablation of TgStx16 causes the similar growth defect like TgVps45 deficiency suggested they work together for the vesicle fusion at TGN. These findings indicate that these two SM proteins are crucial for assembly of pellicle and sub-pellicle network in T. gondii respectively.     

KCTD10 interacts with proliferating cell nuclear antigen and its down‐regulation could inhibit cell proliferation

A novel gene (GenBank accession No. AF113208) named KCTD10 (potassium channel tetramerisation domain‐containing 10) was cloned from our 5300 EST database of human aorta cDNA library. Computational analysis showed that KCTD10 cDNA is 2,638 bp long, encoding 313 amino acids with a proliferating cell nuclear antigen binding motif, mapped to chromosome 12q24.11 with 7 exons, ubiquitously expressed in all 12 tested normal tissues and 7 of 8 tested tumor cell lines from MTN membranes by Northern blot. Nuclear localization of KCTD10 was observed in A549 cells. Yeast two‐hybrid analysis and immunoprecipitation assay showed that KCTD10 can interact with PCNA. In A549 cells, KCTD10 down‐regulation could inhibit cell proliferation, but its over‐expression could not influence cell proliferation. The results suggest that KCTD10 may be associated with DNA synthesis and cell proliferation. J. Cell. Biochem. 106: 409–413, 2009. © 2009 Wiley‐Liss, Inc.     

Terahertz Time-Domain Spectroscopy of Four Hydroxycinnamic Acid Derivatives

The well-resolved absorption spectra of the hydroxycinnamic acid (HCA) derivatives, caffeic acid, ferulic acid, sinapic acid and chlorogenic acid, were measured over the frequency region from 0.3 to 2.0 THz at 294 K with terahertz time-domain spectroscopy (THz-TDS). Theoretical calculation was applied to assist the analysis and assignment of the individual THz absorption spectra of the HCA derivatives with density functional theory (DFT). The distinctive spectral features were originated from the collective motion of molecules held together by hydrogen bonds. The real and imaginary parts of dielectric function of the four HCA derivatives were also obtained.     

Computational model of response maps in the dorsal cochlear nucleus

The neurons in the mammalian (gerbil, cat) dorsal cochlear nucleus (DCN) have responses to tones and noise that have been used to classify them into unit types. These types (I–V) are based on excitatory and inhibitory responses to tones organized into plots called response maps (RMs). Type I units show purely excitatory responses, while type V units are primarily inhibited. A computational model of the neural circuitry of the mammalian DCN, based on the MacGregor neuromime, was used to investigate RMs of the principal cells (P-cells) that represent the fusiform and giant cells. In gerbils, fusiform cells have been shown to have primarily type III unit response properties; however, fusiform cells in the cat DCN are thought to have type IV unit response properties. The DCN model is based on a previous computational model of the cat (Hancock and Voigt Ann Biomed Eng 27: 73–87, 1999) and gerbil (Zheng and Voigt Ann Biomed Eng 34: 697–708, 2006) DCN. The basic model for both species is architecturally the same, and to get either type III unit RMs or type IV unit RMs, connection parameters were adjusted. Interestingly, regardless of the RM type, these units in gerbils and cats show spectral notch sensitivity and are thought to play a role in sound localization in the median plane. In this study, further parameter adjustments were made to systematically explore their effect on P-cell RMs. Significantly, type I, type III, type III-i, type IV, type IV-T and type V unit RMs can be created for the modeled P-cells. Thus major RMs observed in the cat and gerbil DCN are recreated by the model. These results suggest that RMs of individual DCN projection neurons are the result of specific assortment of excitatory and inhibitory inputs to that neuron and that subtle differences in the complement of inputs can result in different RM types. Modulation of the efficacy of certain synapses suggests that RM type may change dynamically.     

Integrating multiple references for single-cell assignment

Efficient single-cell assignment is essential for single-cell sequencing data analysis. With the explosive growth of single-cell sequencing data, multiple single-cell sequencing data sources are available for the same kind of tissue, which can be integrated to further improve single-cell assignment; however, an efficient integration strategy is still lacking due to the great challenges of data heterogeneity existing in multiple references. To this end, we present mtSC, a flexible single-cell assignment framework that integrates multiple references based on multitask deep metric learning designed specifically for cell type identification within tissues with multiple single-cell sequencing data as references. We evaluated mtSC on a comprehensive set of publicly available benchmark datasets and demonstrated its state-of-the-art effectiveness for integrative single-cell assignment with multiple references.     

Evidence for a cross-linking mechanism underlying glucose-induced contraction of phenylboronate hydrogel

The glucose-dependent cross-linking of phenylboronate gels was investigated in order to understand the principle underlying glucose-induced hydrogel contraction. Glucose conformation upon binding to phenylboronates in aqueous solution was also examined and a 1:2 glucofuranose: boronate model was suggested by the results obtained.