Selection and stability validation of reference gene candidates for transcriptional analysis in Rousettus aegyptiacus

From stability to reliability: Unveiling the un-biased reference genes in porcine ovarian granulosa cells under different conditions

Selection of optimal reference genes (RGs) is fundamental for functional genomics studies and gene expression analysis, which are two main approaches to identify functional genes and their expression patterns. However, no systematic study has identified the suitable RGs in porcine ovarian granulosa cells (GCs) which are essential for follicle fate and sow fertility. In this study, the expression profiles of 12 widely-used RGs (GAPDH, RPLP0, ACTB, TUBA1B, EIF3K, PPIA, ATP5F1, B2M, HPRT1, UBC, RPS3, and EEF1A1) in porcine GCs during follicular development and under different abiotic stresses were systematically investigated. Expression stability of the candidate RGs were comprehensively accessed by five statistical algorithms including ΔCt, NormFinder, BestKeeper, geNorm, and RefFinder, indicating that RPS3 and PPIA are the optimal RGs during follicular development, EEF1A1 and RPLP0 are most stable under oxidative stress and inflammation, while ATP5F1, B2M, and RPS3 have higher stability under starvation and heat stress. Notably, the most commonly used RGs (ACTB, GAPDH, and TUBA1B) exhibited low stability in GCs. Reliability of stable RGs was verified by RT-qPCR and showed that selection of the stable RGs significantly improved the detection accuracy of qPCR, which confirms once again that the stability of RGs should not be taken for granted. Our findings identified optimal RG sets in porcine GCs under different conditions, which is helpful in future studies to accurately identify the key regulators and their expression patterns during follicular development in sows.

Transcription profiles and phenotype reveal global response of Staphylococcus aureus exposed to ultrasound and ultraviolet stressors

Ultrasound and ultraviolet light have good inactivation performance against pathogens in sewage. In this study, the inactivation mechanisms of 60 kHz ultrasound and ultraviolet radiation against Staphylococcus aureus (S. aureus) were studied from the perspectives of cell phenotype and transcriptome for the first time. The results showed that both ultrasound and ultraviolet treatments had adverse impacts on the cellular morphology of S. aureus to varying degrees at cellular level. The transcriptomic analysis revealed that there were 225 and 1077 differentially expressed genes (DEGs) in the ultrasound and ultraviolet treatments, respectively. The result revealed that both ultrasound and ultraviolet could interfere with the expression of the genes involved in ABC transporters, amino acid and fatty acid metabolism to influence the membrane permeability. Besides the membrane permeability, ultraviolet also could disturb the ATP synthesis, DNA replication and cell division through restraining the expression of several genes related to carbohydrate metabolism, peptidoglycan synthesis, DNA-binding/repair protein synthesis. Compared with the single inactivation pathway of ultrasound, ultraviolet inactivation of S. aureus is multi-target and multi-pathway. We believe that the bactericidal mechanisms of ultrasound and ultraviolet radiation presented by this study could provide theoretical guidance for the synergistic inactivation of pathogens in sewage by ultrasound and ultraviolet radiation in the future.

Evaluation and validation of reference genes for RT-qPCR gene expression in Naegleria gruberi

Naegleria gruberi is a free-living amoeboflagellate commonly found in freshwater and in soils around the world. It is a non-pathogenic relative of Naegleria fowleri, which is the etiologic agent of Primary Amoebic Meningoencephalitis (PAM). PAM occurs world-wide and it is considered a rare disease, but its fatality rate is high (96%) mainly because of delay in initiation of treatment due to misdiagnosis and lack of a specific treatment. The analysis of gene expression by quantitative real-time PCR in N. gruberi could be a highly efficient means to understand the pathogenicity of N. fowleri and also to find drug targets. Accurate RT-qPCR analysis requires correct normalization of gene expression data using reference genes (RG), whose expression should be constant under different experimental conditions. In this study, six genes, representing the most frequently used housekeeping genes, were selected for evaluation as reference genes in N. gruberi. The expression and stability of these genes was evaluated employing four algorithms (geNorm, NormFinder, BestKeeper and RefFinder). This work shows significant variations of the stability of RGs depending on the algorithms employed and on the experimental conditions (i.e. logarithmic, stationary, heat-shock and oxidative stress). The geNorm, NormFinder and RefFinder analysis of all the experimental conditions in combination revealed that ACT and G6PD were the most stable RGs. While BestKeeper analysis showed that 18S and TBP were the most stable RGs. Moreover, normalization of HSP90 gene expression with the most stable RGs resulted in an upregulation whereas when the normalization was done with the unstable RGs, the gene expression was not reliable. Hence, the implications of this study are relevant to gene expression studies in N. gruberi.