One-step vs. two-step RT-qPCR—tips for choosing the right protocol

Introduction

Not sure whether to use a one-step or a two-step reverse transcription protocol? We’re here to help. Real-time PCR (qPCR) is a powerful and common technique for accurate analysis of gene expression. When starting with RNA samples, you first need to perform a reverse transcription (RT) step in order to generate cDNA for the qPCR experiment. In one-step RT-qPCR, the RT step takes place in the same tube as the qPCR. In two-step RT-qPCR, the RT and qPCR steps take place in separate tubes. Both techniques have advantages and limitations, so it is essential to consider which protocol suits your workflow.

One-step RT-qPCR workflow

The advantages

• Simple and rapid
• Works well when performing a small number of assays
• Amenable to high-throughput applications

In general, one-step RT-qPCR is best suited for high-speed, high-throughput applications. The single-tube protocol is easy to set up and can be used for processing many samples using liquid handlers or other high-throughput systems. This allows for less hands-on-time and reduces the chances of pipetting errors or contamination. The one-step approach works best when used in workflows containing many samples with a limited number of targets.

The limitations

• Unable to optimize RT step
• Does not generate stocks of cDNA

However, one-step RT-qPCR has some limitations. Since both the RT and qPCR steps take place in the same tube, the reaction conditions cannot be optimized separately. This can lead to lower yields or efficiency in either step. Another limitation is that all the cDNA generated is used up in the subsequent qPCR step. This means that no stocks of cDNA can be banked for further validation or experimentation.

Two-step RT-qPCR workflow

The advantages

• High sensitivity, works well with limited sample input
• Able to optimize RT and qPCR steps separately
• Can generate cDNA stocks

Two-step RT-qPCR is best suited for applications requiring flexibility and sensitivity. The two-tube protocol makes it possible to optimize the RT and qPCR steps separately, ensuring maximum specificity and efficiency. This approach works best with workflows analyzing many targets in fewer samples. Another advantage is that two-step RT-qPCR generates cDNA in a separate tube from the qPCR reaction. This allows cDNA stocks to be banked so that they can be used for additional targets or validation.

The limitations

• More time-consuming
• Less amenable to high-throughput applications

Two-step RT-qPCR has some limitations as well. In general, the protocols are more time-consuming and involve more pipetting steps. This introduces more variability and increases the risk of contamination. Additionally, while the ability to optimize both the RT and qPCR steps separately can improve sensitivity and efficiency, it comes with the drawback of having to optimize two reactions instead of one. Lastly, the two-tube protocol cannot be as easily adapted to automated, high-throughput workflows, necessitating more hands-on-time.

Summary

Choosing the right protocol is critical for ensuring optimal performance and consistency. Generally, one-step RT-qPCR is best suited for applications requiring high-speed and high-throughput amplification of many samples with few targets, at the cost of potential efficiency and yield. Two-step RT-qPCR excels at allowing optimization, which provides greater sensitivity and flexibility, but reduces throughput. Depending on your workflow and needs, one of these reverse transcription protocols may be a better choice than the other. Explore our selection guide to find the right kit for your application.