LETTER

SNPs deciding the rapid growth of are alterable LETTER Jie Zhoua and Yin Lia,1

Cyanobacteria researchers are keen to understand cyanobacteria strains were grown under a high light

why elongatus UTEX 2973 (Synecho- intensity of 500 μE or 800 μE, at 38 °C, with 5% CO2. coccus 2973) can grow more than two times faster Two independent experiments and sequencing were than Synechococcus elongatus PCC 7942 (Synecho- performed. coccus 7942), as their sequences share 99.8% To our great surprise, no SNP was found in the identity (1). atpA gene, in either S. 2973-1 or S. 7942 HL-1. E260D A recent paper in PNAS by Ungerer et al. (2) gives in Ppnk and Q121R/E134K in RpaA were found in S. an answer. The authors investigate the molecular de- 2973-1, which is consistent with what Ungerer et al. (2) terminants accounting for the rapid growth of Syne- describe for Synechococcus 2973, while Q121R in chococcus 2973. They believe that the rapid growth of RpaA was found in S. 7942 HL-1. This SNP is described Synechococcus 2973 is decided by four SNPs in three in Synechococcus 2973 (2), but not in Synechococcus proteins, namely C252Y in AtpA, E260D in Ppnk, and 7942 HL (3). Q121R/E134K in RpaA. In our laboratory, S. 7942 HL-1 grows as fast as S. In a separate study, Lou et al. (3) coincidently 2973-1 under a high light intensity of 500 μEor

obtained a Synechococcus 7942 mutant (designated 800 μE, at 38 °C, with 5% CO2. However, the SNPs here as Synechococcus 7942 HL), which can grow detected were inconsistent with the published data equally fast compared with that of Synechococcus (2, 3). Our results suggest that the SNPs, which 2973, irrespective of light intensity. Lou et al. indi- were thought to determine the rapid growth of cyano- cated that a single SNP in AtpA (C252Y) accounts for , are alterable. the increased growth rate of Synechococcus 7942 HL. Thus, we argue that the relationship between Is one mutation (C252Y in AtpA) sufficient to create SNPs and the rapid growth requires further investi- a cyanobacterium mutant growing as fast as Synecho- gation. Perhaps an integrated analysis incorporat- coccus 2973? With this question, we sequenced ing SNPs with data from the genome-scale fluxome (according to ref. 2) the genes atpA, ppnK, and rpaA (4) and transcriptome (5) of Synechococcus 2973 would in Synechococcus 2973 and Synechococcus 7942 HL help gain further insight into the molecular mechanism stored in our laboratory (designated S. 2973-1 and underpinning the rapid growth of Synechococcus 2973. S. 7942 HL-1, respectively). Synechococcus 2973 was purchased from the Culture Collection of Algae at Acknowledgments This work was supported by the Key Research Program of the the University of Texas at Austin, and Synechococcus Chinese Academy of Sciences (ZDRW-ZS-2016-3 to Y.L. and 7942 HL was gift from Xuefeng Lu, Chinese J.Z.), and the National Natural Science Foundation of China Academy of Sciences, Qingdao, China (3). Both (31670048 to J.Z.).

1 Yu J, et al. (2015) Synechococcus elongatus UTEX 2973, a fast growing cyanobacterial chassis for biosynthesis using light and CO2. Sci Rep 5:8132. 2 Ungerer J, Wendt KE, Hendry JI, Maranas CD, Pakrasi HB (2018) Comparative genomics reveals the molecular determinants of rapid growth of the cyanobacterium Synechococcus elongatus UTEX 2973. Proc Natl Acad Sci USA 115:E11761–E11770. 3 Lou W, et al. (2018) A specific single nucleotide polymorphism in the ATP synthase gene significantly improves environmental stress tolerance of Synechococcus elongatus PCC 7942. Appl Environ Microbiol 84:e01222–e01218. 4 Hendry JI, et al. (2018) Genome-scale fluxome of Synechococcus elongatus UTEX 2973 using transient 13C-labeling data. Plant Physiol 01357.2018. 5 Tan X, et al. (2018) The primary transcriptome of the fast-growing cyanobacterium Synechococcus elongatus UTEX 2973. Biotechnol Biofuels 11:218.

aChinese Academy of Sciences Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China Author contributions: J.Z. and Y.L. designed research; J.Z. performed research; J.Z. and Y.L. analyzed data; and J.Z. and Y.L. wrote the paper. The authors declare no conflict of interest. Published under the PNAS license. 1To whom correspondence should be addressed. Email: [email protected]. Published online February 12, 2019.

www.pnas.org/cgi/doi/10.1073/pnas.1900210116 PNAS | March 5, 2019 | vol. 116 | no. 10 | 3945 Downloaded by guest on September 30, 2021