Application of Single-Cell Assay for Transposase-Accessible Chromatin with High Throughput Sequencing in Plant Science: Advances, Technical Challenges, and Prospects.

The Single-cell Assay for Transposase-Accessible Chromatin with high throughput sequencing (scATAC-seq) has gained increasing popularity in recent years, allowing for chromatin accessibility to be deciphered and gene regulatory networks (GRNs) to be inferred at single-cell resolution. This cutting-edge technology now enables the genome-wide profiling of chromatin accessibility at the cellular level and the capturing of cell-type-specific cis-regulatory elements (CREs) that are masked by cellular heterogeneity in bulk assays. Additionally, it can also facilitate the identification of rare and new cell types based on differences in chromatin accessibility and the charting of cellular developmental trajectories within lineage-related cell clusters. Due to technical challenges and limitations, the data generated from scATAC-seq exhibit unique features, often characterized by high sparsity and noise, even within the same cell type. To address these challenges, various bioinformatic tools have been developed. Furthermore, the application of scATAC-seq in plant science is still in its infancy, with most research focusing on root tissues and model plant species. In this review, we provide an overview of recent progress in scATAC-seq and its application across various fields. We first conduct scATAC-seq in plant science. Next, we highlight the current challenges of scATAC-seq in plant science and major strategies for cell type annotation. Finally, we outline several future directions to exploit scATAC-seq technologies to address critical challenges in plant science, ranging from plant ENCODE(The Encyclopedia of DNA Elements) project construction to GRN inference, to deepen our understanding of the roles of CREs in plant biology.

Membrane stretch and cytoplasmic Ca2+ independently modulate stretch-activated BK channel activity.

Large conductance Ca(2+)-activated K(+) (BK) channels are responsible for changes in chemical and physical signals such as Ca(2+), Mg(2+) and membrane potentials. Previously, we reported that a BK channel cloned from chick heart (SAKCaC) is activated by membrane stretch. Molecular cloning and subsequent functional characterization of SAKCaC have shown that both the membrane stretch and intracellular Ca(2+) signal allosterically regulate the channel activity via the linker of the gating ring complex. Here we investigate how these two gating principles interact with each other. We found that stretch force activated SAKCaC in the absence of cytoplasmic Ca(2+). Lack of Ca(2+) bowl (a calcium binding motif) in SAKCaC diminished the Ca(2+)-dependent activation, but the mechanosensitivity of channel was intact. We also found that the abrogation of STREX (a proposed mechanosensing apparatus) in SAKCaC abolished the mechanosensitivity without altering the Ca(2+) sensitivity of channels. These observations indicate that membrane stretch and intracellular Ca(2+) could independently modulate SAKCaC activity.

A novel DSPP mutation causes dentinogenesis imperfecta type II in a large Mongolian family.

BACKGROUND: Several studies have shown that the clinical phenotypes of dentinogenesis imperfecta type II (DGI-II) may be caused by mutations in dentin sialophosphoprotein (DSPP). However, no previous studies have documented the clinical phenotype and genetic basis of DGI-II in a Mongolian family from China. METHODS: We identified a large five-generation Mongolian family from China with DGI-II, comprising 64 living family members of whom 22 were affected. Linkage analysis of five polymorphic markers flanking DSPP gene was used to genotype the families and to construct the haplotypes of these families. All five DSPP exons including the intron-exon boundaries were PCR-amplified and sequenced in 48 members of this large family. RESULTS: All affected individuals showed discoloration and severe attrition of their teeth, with obliterated pulp chambers and without progressive high frequency hearing loss or skeletal abnormalities. No recombination was found at five polymorphic markers flanking DSPP in the family. Direct DNA sequencing identified a novel A-->G transition mutation adjacent to the donor splicing site within intron 3 in all affected individuals but not in the unaffected family members and 50 unrelated Mongolian individuals. CONCLUSION: This study identified a novel mutation (IVS3+3A-->G) in DSPP, which caused DGI-II in a large Mongolian family. This expands the spectrum of mutations leading to DGI-II.

Identification of important regions for ethylene binding and signaling in the transmembrane domain of the ETR1 ethylene receptor of Arabidopsis.

The ethylene binding domain (EBD) of the Arabidopsis thaliana ETR1 receptor is modeled as three membrane-spanning helices. We surveyed ethylene binding activity in different kingdoms and performed a bioinformatic analysis of the EBD. Ethylene binding is confined to land plants, Chara, and a group of cyanobacteria but is largely absent in other organisms, consistent with our finding that EBD-like sequences are overrepresented among plant and cyanobacterial species. We made amino acid substitutions in 37 partially or completely conserved residues of the EBD and assayed their effects on ethylene binding and signaling. Mutations primarily in residues in Helices I and II midregions eliminated ethylene binding and conferred constitutive signaling, consistent with the inverse-agonist model of ethylene receptor signaling and indicating that these residues define the ethylene binding pocket. The largest class of mutations, clustered near the cytoplasmic ends of Helices I and III, gave normal ethylene binding activity yet still conferred constitutive signaling. Therefore, these residues may play a role in turning off the signal transmitter domain of the receptor. By contrast, only two mutations were loss of function with respect to signaling. These findings yield insight into the structure and function of the EBD and suggest a conserved role of the EBD as a negative regulator of the signal transmitter domain.