Biology subjects

Xiong, M.

Publications and source records attributed to Xiong, M..

22 records · Page 2Linked to original sources

bioRxiv2021

A method for simultaneously monitoring phloem and xylem reconnections in grafted watermelon seedlings

Grafting is an effective way to increase watermelon tolerance to biotic and abiotic stresses. However, the survival of grafted seedlings largely depends on successful graft formation. Therefore, understanding the graft formation process, particularly the vascular reconnection process is of critical importance. This study found that lignin in watermelon stem shows strong auto-fluorescence under blue-light excitation which makes blue-light excited fluorescent tracers (FTs) such as 5(6)-carboxy fluorescein diacetate (CFDA) become unsuitable for assaying vascular connectivity in watermelon. In contrast, UV-light excited esculin and red-light excited acid fuchsin were proved to be efficient FTs for monitoring the phloem and xylem connectivity, respectively, in self-grafted watermelon. Furthermore, a combined application of esculin to the scion cotyledon and acid fuchsin to the rootstock root enabled simultaneous monitoring of the phloem and xylem connectivity in individual self-grafted watermelon seedlings. In addition, this method is also applicable in investigating the phloem and xylem reconnections in self-grafted melon and cucumber, and heterograft of watermelon, melon and cucumber onto pumpkin rootstock. Based on this established method, we found that phloem and xylem reconnections are not timely separated in self-grafted watermelon. Furthermore, low temperature and removal of the rootstock cotyledons both delayed the vascular reconnection process in watermelon. In conclusion, this new method provides a convenient, accurate and rapid way to analyze the vascular connectivity not only in watermelon, but also in other cucurbit crops.

plant biology↗

bioRxiv2021

The SARS-CoV-2 transcriptome and the dynamics of the S gene furin cleavage site in primary human airway epithelia

The novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) caused the devastating ongoing coronavirus disease-2019 (COVID-19) pandemic which poses a great threat to global public health. The spike (S) polypeptide of SARS-CoV-2 consists of the S1 and S2 subunits and is processed by cellular proteases at the S1/S2 boundary. The inclusion of the 4 amino acids (PRRA) at the S1/S2 boundary forms a furin cleavage site (FCS), 682RRAR{downarrow}S686, distinguishing SARS-CoV-2 from its closest relative, the SARS-CoV. Various deletions surrounding the FCS have been identified in patients. When SARS-CoV-2 propagated in Vero cells, the virus acquired various deletions surrounding the FCS. In the present study, we studied the viral transcriptome in SARS-CoV-2 infected primary human airway epithelia (HAE) cultured at an air-liquid interface (ALI) with an emphasis on the viral genome stability at the S1/S2 boundary using RNA-seq. While we found overall the viral transcriptome is similar to that generated from infected Vero cells, we identified a high percentage of mutated viral genome and transcripts in HAE-ALI. Two highly frequent deletions were found at the S1/S2 boundary of the S gene: one is a deletion of 12 amino acids, 678TNSPRRAR{downarrow}SVAS689, which contains the FCS, another is a deletion of 5 amino acids, 675QTQTN679, which is two amino acids upstream of the FCS. Further studies on the dynamics of the FCS deletions in apically released virions revealed that the selective pressure for the FCS maintains the S gene stability in HAE-ALI but with exceptions, in which the FCS deletions are remained at a high rate. Thus, our study presents evidence for the role of unique properties of human airway epithelia in the dynamics of the FCS region during infection of human airways, which is donor-dependent.

microbiology↗

bioRxiv2020

Kidney injury molecule-1 is a potential receptor for SARS-CoV-2

COVID-19 patients present high incidence of kidney abnormalities, which are associated with poor prognosis and high mortality. Identification of SARS-CoV-2 in kidney of COVID-19 patients suggests renal tropism and direct infection. Presently, it is generally recognized that SARS-CoV-2 initiates invasion through binding of receptor-binding domain (RBD) of spike protein to host cell-membrane receptor ACE2, however, whether there is additional target of SARS-CoV-2 in kidney remains unclear. Kidney injury molecule-1 (KIM1) is a transmembrane protein that drastically up-regulated after renal injury. Here, binding between SARS-CoV2-RBD and the extracellular Ig V domain of KIM1 was identified by molecular simulations and co-immunoprecipitation, which was comparable in affinity to that of ACE2 to SARS-CoV-2. Moreover, KIM1 facilitated cell entry of SARS-CoV2-RBD, which was potently blockaded by a rationally designed KIM1-derived polypeptide. Together, the findings suggest KIM1 may mediate and exacerbate SARS-CoV-2 infection in a vicious cycle, and KIM1 could be further explored as a therapeutic target.

cell biology↗

bioRxiv2018

Robust Reference Powered Association Test of genome-wide association studies

Genome-wide association studies (GWAS) have identified abundant genetic susceptibility loci, although they are far less from meeting the previous expectations due to low statistical power and false positive results. Effective statistical methods are required to further improve the analyses of massive GWAS data. Here we presented a new statistic (Robust Reference Powered Association Test, http://drwang.top/gwas.html) to use large public database as reference to reduce concern of potential population stratification. To evaluate the performance of this statistic for various situations, we simulated multiple sets of sample size and frequencies to compute statistical power. Furthermore, we applied our method to several real datasets (psoriasis genome-wide association datasets and schizophrenia genome-wide association dataset) to evaluate the performance. Careful analyses indicated that our newly developed statistic outperformed several previously developed GWAS applications. Importantly, this statistic is more robust than naive merging method in the presence of small control-reference differentiation, therefore likely to detect more association signals.

genetics↗