Nat. Biotechnol. 33, 1103–1108 (2015); published online 28 September 2015; corrected after print 18 December 2018

In the version of this article initially published, the y-axis numbering in Figure 1 was high by a factor of 10; the correct range is 0.5 to 2.5 million nonredundant genes. The error has been corrected in the HTML and PDF versions of the article.