Figures (3)  Tables (2)
    • Figure 1. 

      The basic skeleton structure of cucurbitacin (adapted from Ma[7]).

    • Figure 2. 

      Cucurbitacin biosynthesis process (adapted from Ma[7]). FPS: Fanesyl pyrophosphate synthase; SQS: Squalene synthase; SQE: Oxidoqualene synthase; OSC: Oxidoqualene cyclase; P450: Cytochrome P450 monooxygenase; ACT: Acetyltransferase. The dotted line indicates that there are multiple steps involved.

    • Figure 3. 

      Cucurbitacin B, C, and E gene clusters (adapted from Ma[7]). Orange squares represent OSC family genes, pink squares represent ACT genes, and blue squares represent CYP450 family genes.

    • Species Chr Molecular marker Primer sequence (5'-3') Populations Ref.
      Cucumber 6 SSR02309 (1.7 cm), SSR00004 (2.2 cm) SSR02309-F: TGAAATGCCTCTGCAATGAC 9110Gt (bibi) × 9930 (BiBi)→RILs [9]
      SSR02309-R: TCATGACTAGACACGCCAGC
      SSR00004-F: TTCATTGCAAAGCACACACA
      SSR00004-R: TGAAAAGAGGGAACAAAAGCA
      5 E23M66-101 (5 cm), E25M65-213
      (4 cm)
      E23: GACTGCGTACCAATTCTA 931 (Bt) × 932 (bt)→F2 [42]
      M66: GATGAGTCCTGAGTA
      E25: GACTGCGTACCAATTCTG
      M65: GATGAGTCCTGAGTAAGAG
      5 SSR10795 (0.8 cm), SSR07081 (2.5 cm) SSR10795-F: CATCAAAATACCTCCATCTCCA 46GBt (BiBiBtBt) × 931 (BiBibtbt)→F2 [67]
      SSR10795-R: GCATGAATAGCATGGGGTTT
      SSR07081-F: GGCGACTTTGGAGTGTAACAA
      SSR07081-R: GGAAAGATATTCTCAGGGAATCTAA
      6 SSR0004 (1.9 cm), SSR02309 (3.3 cm) 9110Gt (bi-1bi-1) × 9930 (Bi-1Bi-1)→RILs [10]
      5 SSR12291 (1.9 cm), SSR02118 (1.8 cm) SSR12291-F: CGCACGAGAACCTTTATTGA D9320 (Bt) × D0432-2-2 (bt)→BC1 [36]
      SSR12291-R: TCACATCAAATTAACACTTTCATCTC
      SSR02118-F: TGGATTGTCATCTCATTGGC
      SSR02118-R: GGTGAGTGGTAATTTTATGAATTTTG
      Melon 2, 5 2mBiPr21619699, 2mBiPr21653588, 5mBiPr20403004, 5mBiPr20822407, and 5mBiPr21331862 2mBiPr21619699-F: AATGGCATAACCTTTCACCT C68 (Bt) × C69 (bt)→BC1 [45]
      2mBiPr21619699-R: CTTTCTATCACCAACCGACT
      2mBiPr21653588-F: TTATCTAAGTTTCCTCGGTC
      2mBiPr21653588-R: CTTCAACTTGGATGTTTTCT
      5mBiPr20403004-F: GGAATAGGAATAGGAAGAATGT
      5mBiPr20403004-R: AAAAGGGTTAATGATAAGAGAC
      5mBiPr20822407-F: TAGGTTTAACCTGTTTTCACC
      5mBiPr20822407-R: GCATACAAAGCATTTTTTCTT
      5mBiPr21331862-F: ATGGTGAGCATTGTTTTCGA
      5mBiPr21331862-R: TCTTTTGGGTCTTGGGCTTC
      Watermelon 1 W01-2 (0.93 cm), W01-3 (0.99 cm) W1-1 (bt) × PI 186490 (Bt)→BC1 [52]
      Watermelon 1 SNP3162335, SNP3278961 SNP3162335-F: TGTCAAATGGGTTCATGAAGTT 9904(Bt) × Handel (bt)→RILs [54]
      SNP3162335-R: TTCCTGTCTTTTGTGGTTTGG
      SNP3278961-F: TTCGCACTAACCTGGAAAAG
      SNP3278961-R: ATTTGAAACCCGCCCTTAAA
      Sponge gourd 7 LuBt1-2 (1.9 cm), LuBt1A (1.2 cm) 48-1-0-0 (bt) × 4-0-0-0 (bt)→BC1 [61]
      Sponge gourd 7 SGE292 (6.08 cm), SGC196 (3.11 cm) SGE292-F: TGGGGACAACCCGGCTT 48-1-0-0 (bt) × 4-0-0-0 (bt)→BC1 [62]
      SGE292-R: GACTGCGTACGAATTCTG
      SGC196-F: AGCGAGCAAGCCGGTGG
      SGC196-R: GACTGCGTACGAATTATG
      Bottle gourd 6, 7 BGReSe_09031-BGReSe_09068, BGReSe_11107-BGReSe_11032 Hangzhou Gourd (bt) × Puxian Gourd (bt)→F2 [2]

      Table 1. 

      The bitterness genes of cucurbitaceae crops located in related markers.

    • Gene name Gene ID Gene types Notes Structure of Cucurbitacins
      Cucurbitacin B CmBi Melo3C022374 OSC Cucurbitadienol synthase
      CmACT Melo3C022373 ACT Acyltransferase
      Cm160 Melo3C022377 CYP81Q58
      Cm170 Melo3C022376 CYP89A140
      Cm180 Melo3C022375 CYP81Q59 C2 hydroxylase
      Cm710 Melo3C022372 CYP87D19
      Cm890 Melo3C002192 CYP87D20 C11 carbonylase + C20 hydroxylase
      Cm490 Melo3C023960 CYP712D8
      CmBt Melo3C005611 bHLH TF Specifically expressed in fruits
      CmBr Melo3C005610 bHLH TF Specifically expressed in roots
      Cucurbitacin C CsBi Csa6G088690 OSC Cucurbitadienol synthase
      CsACT Csa6G088700 ACT Acyltransferase
      Cs160 Csa6G088160 CYP81Q58 19,25-Dihydroxy-cucurbitadienol
      Cs170 Csa6G088170 CYP89A140
      Cs710 Csa6G088710 CYP89D19
      Cs490 Csa3G698490 CYP712D8
      Cs540 Csa3G903540 CYP88L2 19-Hydroxy-cucurbitadienol
      Cs550 Csa3G903550 CYP88L3
      Cs890 Csa1G044890 CYP87D20
      CsBt Csa5G157230 bHLH TF Specifically expressed in fruits
      CsBl Csa5G156220 bHLH TF Specifically expressed in leaves
      Cucurbitacin E ClBi Cla007080 OSC Cucurbitadienol synthase
      ClACT Cla007081 ACT Acyltransferase
      Cl160 Cla007077 CYP81Q58
      Cl170 Cla007078 CYP89A140
      Cl180 Cla007079 CYP81Q59 C2 hydroxylase
      Cl710 Cla007082 CYP89D19
      Cl890A Cla008355 CYP87D20 C11 carbonylase + C20 hydroxylase
      Cl890B Cla008354 CYP87D20 C11 carbonylase + C20 hydroxylase
      Cl490 Cla017252 CYP712D8
      Cl510 Cla016164 CYP88A60
      ClBt Cla011508 bHLH TF Specifically expressed in fruits
      ClBr Cla011510 bHLH TF Specifically expressed in roots

      Table 2. 

      Gene related to biosynthesis and regulation of cucurbitacin B, C, and E in melon, cucumber, and watermelon.