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.