Supersweet and waxy: meeting the diverse demands for specialty maize by genome editing

SH2 and BT2 are the large (SH2) and small (BT2) subunit of ADP‐glucose Pyrophosphorylase genes; GBSS, the WAXY gene encodes the enzyme GRANULE BOUND STARCH SYNTHASE; SS, the soluble starch synthase genes; SBE, starch branching enzyme genes; DBE, the debranching enzyme genes; Red crosses represent CRISPR/Cas9 targeted‐knockout activity. (b) The CRISPR/Cas9 construct to target the SH2 and WX genes in duplex. Bar, bialaphos resistance marker; E35S, 35S CaMV promoter; LB, T‐DNA left border; NLS, nuclear location signal sequence; Nos, Nos terminator; RB, T‐DNA right border; sgRNA‐SH2, single‐guide RNA targeting the SH2 gene; sgRNA‐WX, single‐guide RNA targeting the WX gene; Ubi, the promoter of the ubiquitin 1 gene; U6‐2, the maize endogenous U6 PolIII promoter. (c) and (d) The targeted mutations on the SH2 (c) and WX (d) genes. Counts, variant counts identified in 52 T1 events; Nucleotide sequence in red shows the mutations; PAM, proto‐spacer‐motif; Red dash in sequence, deletions; Blue sequence, the sgRNA location; Sequence underlined, the PAM sequence; sgRNA, single‐guide RNA; Var., variants of identified mutations; WT, the wild type. (e) and (f) The diagram of the genetic basis for SWC production (e) and the morphology of corn ears from genome edited lines (f).Texts in red indicate supersweet traits and genotypes while those in blue indicate waxy traits and genotypes. Acknowledgements This work was supported by grants from Beijing Municipal Science and Technology (Major Program D171100007717001), the Key Area Research and Development Program of Guangdong Province (2018B020202008), the China National Major Research and Development Program (2016YFD0101803), the National Science Foundation of China (No. 31771808) and the National Engineering Laboratory for Crop Molecular Breeding.