The evidence for anthocyanins in the betalain-pigmented genus Hylocereus is weak

Here we respond to Zhou (BMC Genomics 21:734, 2020) "Combined Transcriptome and Metabolome analysis of Pitaya fruit unveiled the mechanisms underlying peel and pulp color formation" published in BMC Genomics. Given the evolutionary conserved anthocyanin biosynthesis pathway in betalain-pigmented species, we are open to the idea that species with both anthocyanins and betalains might exist. However, in absence of LC-MS/MS spectra, apparent lack of biological replicates, and no comparison to authentic standards, the findings of Zhou (BMC Genomics 21:734, 2020) are not a strong basis to propose the presence of anthocyanins in betalain-pigmented pitaya. In addition, our re-analysis of the datasets indicates the misidentification of important genes and the omission of key flavonoid and anthocyanin synthesis genes ANS and DFR. Finally, our re-analysis of the RNA-Seq dataset reveals no correlation between anthocyanin biosynthesis gene expression and pigment status.