About a month ago, we reported on a retraction by Pamela Ronald, of the University of California, Davis, and colleagues. We noted then that this was a case of scientists doing the right thing. Ronald contacted us after that post ran, and let us know that there would be another retraction shortly. That retraction notice has now appeared, in Science:
AS A RESULT OF ADDITIONAL EXPERIMENTS IN P.C.R.S AND S.W.-L.S LABORATORIES, WE WISH TO retract our 2009 Report, A type Isecreted, sulfated peptide triggers XA21-mediated innate immunity (1). Specifically, we have not been able to consistently reproduce the results shown in Figure 3. We have also discovered critical errors in Figures 2 and S3. The strain PXO99∆ax21, used in Figure 2, was mixed up with another strain (PXO99∆raxSt). When we repeated the experiment with the validated PXO99∆ax21 insertion mutant, this strain is still avirulent on Xa21 lines. These results indicate that this insertion in Ax21 does not abolish the ability of PX099 to trigger XA21-mediated immunity. Regarding fi gure S3, by using more sensitive methods, we have discovered that Ax21 is also secreted in the mutant strains PXO99∆raxA and PXO99∆raxC. Although we recognize that some parts of this paper may remain valid, we note that key parts of the work depend on the results of Figures 2 and 3. For these reasons, we retract the main conclusion of the paper that a type Isecreted, sulfated peptide triggers XA21-mediated innate immunity.
The paper has been cited 131 times, according to Thomson Scientific’s Web of Knowledge.
In a blog post at Scientific American timed for the publication of the notice today, Ronald explains what happened. Excerpt:
For me, there was never any question that I would correct the scientific record if we had made a mistake. The bigger challenge was confirming that we really had made mistakes and generating sufficient evidence to warrant full retraction of the papers.
There were two important factors to consider. A delay in the retraction would waste the time of my colleagues who wanted to replicate our assays and build on our work. But publishing a hasty retraction with insufficient evidence would be equally counterproductive. I therefore needed to figure out how to strike the right balance between getting the answer right and getting the word out that our research may be flawed. I discussed these issues with the journal editors early in the process. They agreed that caution was important and graciously allowed us ample time to carry out further experimentation. Although at first I planned to repeat all 25-plus experiments in the papers, it soon became clear that this would be impossible to accomplish within a reasonable time frame. In April, at an international plant immunity meeting, I announced that we had made errors, that we were questioning some of our conclusions, and that I was working with the journal editors to publish a statement as soon as possible.
Sorting out the situation was personally and professionally painful for all involved. Instead of advancing the science in new directions as we’d planned, it was necessary to backtrack: re-isolate bacterial strains, optimize greenhouse conditions, and repeat experiments. Former lab members who had begun new positions as professors in Korea and Thailand were devastated to learn that the researchers in my lab could not repeat their work. Junior scientists in the laboratory worried their careers would be tarnished, and understandably did not want to spend too much time on the “clean-up” operation. I therefore assigned the bulk of the work of replication to experienced, highly qualified staff scientists, which took time away from their own projects but helped the junior scientists move to projects that were not affected by errors. It took persistence, courage and confidence to stick together as a team throughout this challenging year. I am proud that we were able to do this.
The process even touched our families. My 6th grade daughter sent me an email with this subject line: “Everyone makes misktakes” and linked to a relevant story she had found in the news: Helium, not so super after all!
Ronald writes that the team will soon report the latest results in the Ax21 story. The whole post is definitely worth a read.