Y Xia

Publications (3)8.08 Total impact

• Article: Vacuolar ATPase subunit H is essential for the survival and moulting of Locusta migratoria manilensis.

  C Li, Y Xia
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  ABSTRACT: Vacuolar (H(+) )-ATPase (V-ATPase) functions as an electrogenic pump, transporting protons from the cytoplasm to the extracellular fluid to generate cell-negative membrane voltage. The V-ATPase subunit H, encoded by Vhasfd, is required for V-ATPase activity. In this study, the gene encoding V-ATPase subunit H from Locusta migratoria manilensis was cloned, and designated as Lm-Vhasfd. The complete cDNA sequence is 2018 bp, with an open reading frame encoding 515 amino acid residues. Semi-quantitative reverse transcription PCR (RT-PCR) showed that Lm-Vhasfd transcription is high in the haemolymph, midgut, trunk and leg, but relatively low in the fat body and head tissues. Injection with a specific double-strand RNA (dsRNA) led to a significant decrease in Lm-Vhasfd mRNA, V-ATPase enzyme activity and ATP concentration. Bioassays showed that silencing Lm-Vhasfd led to the death of individuals and various moulting defects. The accumulative mortality of the RNA interference (RNAi) mutant 11 days post-injection was 96.7%, which was conspicuously higher than that seen in wild type locusts. These RNAi phenotypes demonstrate that Lm-Vhasfd is essential for the growth and moulting of L. migratoria manilensis.
  Insect Molecular Biology 05/2012; 21(4):405-13. · 2.53 Impact Factor
• Article: Development and application of molecular‐based diagnosis for ‘Candidatus Liberibacter asiaticus’, the causal pathogen of citrus huanglongbing

  Z. Wang, Y. Yin, H. Hu, Q. Yuan, G. Peng, Y. Xia
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  ABSTRACT: Conventional PCR and two real-time PCR (RTi-PCR) methods were developed and compared using the primer pairs CQULA03F/CQULA03R and CQULA04F/CQULA04R, and TaqMan probe CQULAP1 designed from a species-specific sequence of the rplJ/rplL ribosomal protein gene, for diagnosis of citrus huanglongbing (HLB) disease in southern China. The specificity and sensitivity of the three protocols for detecting ‘Candidatus Liberibacter asiaticus’ in total DNA extracts of midribs collected from infected citrus leaves with symptoms in Guangxi municipality, Jiangxi Province and Zhejiang Province, were tested. Sensitivities using extracted total DNA (measured as copy number, CN per µL of recombinant plasmid solution) were 439·0 (1·30 × 105 CN µL−1), 4·39 (1·30 × 103 CN µL−1) and 0·44 fg µL−1 (1·30 × 102 CN µL−1) for conventional PCR, TaqMan and SYBR Green I (SGI) RTi-PCR, respectively. SGI RTi-PCR was the most sensitive, but its specificity needed to be confirmed by running a melt-curve assay. The TaqMan RTi-PCR assay was rapid and had the greatest specificity. Concerning the correlation of PCR detection results with the various HLB symptoms, uneven mottling of leaves had the highest positive rate (96·50%), indicating that leaf mottling was the most reliable symptom for field surveys. Dynamic analysis results from the TaqMan assays showed that the titre (CN) g−1 citrus tissue of ‘Ca. L. asiaticus’ was highest between October and December (threshold cycle (Ct) average = 29·3, CN = 3·35 × 107) and lowest between March and May (Ct average = 32·0, CN = 5·10 × 106) in 2004 and 2005. The optimized molecular-based assays should prove useful for presymptom diagnosis of HLB disease, monitoring and identification of ‘Ca. L. asiaticus’, and field epidemic regulation.
  Plant Pathology 08/2006; 55(5):630 - 638. · 2.13 Impact Factor
• Article: Mechanism of RNA 2'-O-methylation: evidence that the catalytic lysine acts to steer rather than deprotonate the target nucleophile.

  C Li, Y Xia, X Gao, P D Gershon
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  ABSTRACT: The weight of current evidence suggests that RNA 2'-O-MTases employ an S(N)2 mechanism with an in-line attack of the target nucleophile upon the methyl group of the AdoMet cofactor. It has been suggested that, like the phosphohydrolytic enzymes, ribozymes, and nucleic acid polymerases, the RNA 2'-O-MTases initially activate the substrate's attacking hydroxyl oxygen by deprotonation. Here, evidence is presented that the vaccinia virus mRNA cap specific 2'-O-MTase VP39 does not promote RNA 2'-oxyanion formation but that instead it acts by steering a hydroxyl oxygen orbital toward the cofactor methyl center.
  Biochemistry 06/2004; 43(19):5680-7. · 3.42 Impact Factor