Screening and validation of reference genes for quantitative RT-PCR analysis in Ampelopsis grossedentata / 中草药

Objective: To screen reference genes for real time quantitative PCR (qRT-PCR) research in Ampelopsis grossedentata. Methods: On the basis of the conserved sequences among plant species, six candidate reference genes (including Actin, 18 S-rRNA, GAPDH, α-Tubulin, β-Tubulin, and UBQ) were cloned from A. grossedentata by RT-PCR in this study. The expression stability of each reference gene in different tissues (shoot tip, young leaf, mature leaf, old leaf, stem, and root) were analyzed by three softwares (GeNorm, NormFinder, and BestKeeper), followed by validation of the expression pattern of AgPAL by qRT-PCR. Results: Actin, 18 S-rRNA, and GAPDH expressed most stably in all samples and were suitable for reference genes, which were further confirmed by the transcript level analysis result of AgPAL in different tissues. Conclusion: This is the first report on the screening and validation of reference genes for qRT-PCR in A. grossedentata, which benefits future studies on gene expression in this species.

Q2N and E64G double mutation of ubiquitin confers a stress sensitive phenotype on Saccharomyces cerevisiae.

The eukaryotic protein, ubiquitin harbours a parallel β-bulge in its structure which is formed by residues Glu64(1), Ser65(2) and Gln2(X). Despite their low % frequency of occurrence in parallel β-bulges, the residues Gln2 and Glu64 have been totally conserved in ubiquitin. In a previous study, two single mutants UbQ2N and UbE64G were constructed by replacing the residues Gln2 and Glu64 with Asn and Gly, respectively to understand their importance. The choice of the residues for substitution was made on the basis of their high preference for existence in parallel β-bulge, so that the structure of mutants remains unaltered and any functional differences observed would highlight the importance of Gln2 and Glu64 in ubiquitin biology. The results from this study established that yeast cells expressing either UbQ2N or UbE64G, displayed functional differences with respect to survival upon exposure to cycloheximide and degradation of substrates by ubiquitin fusion degradation (UFD) pathway. It describes construction of the double mutant UbQ2N-E64G and its characterization. Our results showed expression of UbQ2N-E64G in stress hypersensitive SUB60 cells led to significant decrease in growth rate and prolonged half-life of substrates of UFD pathway, besides failure of complementation under heat and antibiotic stresses, providing the reason for conservation of Gln2 and Glu64 in ubiquitin sequence.