Figures (1)  Tables (7)

    • Figure 1. 

      Schematic diagram of the molecular regulatory network involved in plant wax biosynthesis, hormone signaling, and systemic acquired resistance.

    • Wax component Core components Regulatory genes Ref.
      Alkanes: C25–C33 (odd carbons) C29, C31 SlCER1/3, SlCER6, SlKCS8/SlKCS10, SIFIS1, SlCER1-1 [16−21]
      Primary alcohols: C22–C30 C26, C28, C30 SlFARs, SlLACS1, SlABCG11, SlWRKY33, SlbHLH51 [22−24]
      Fatty acids: C16–C30 C16:0, C18:0, C20:0 SlLACS1, SlFIS1, SlKCS1 [20−22,25]
      Triterpenoids α-Amyrin, β-amyrin, lupeol, taraxerol SlTTS1, SlMYB75, SIFIS1 [21,26,27]
      Other components Sugar esters (glucose esters, sucrose esters) − [16]

      Table 1. 

      Analysis of wax components and regulatory genes in tomato.

    • Wax component Core components Regulatory genes Ref.
      Alkanes: C25–C33 (odd carbons) C29, C31 MdCER1, MdCER3, MdHDG5, MdERF2, MdSHN1 [28−32]
      Primary alcohols: C22–C30 (even carbons) C28, C30 MdMYB96, MdFAR1/MdFAR4 [33]
      Fatty acids: C16–C26 C16:0, C18:0 MdLACS2/MdLACS4, MdKCS1/MdKCS10, MdWRI4 [28,34]
      Triterpenoids Oleanolic acid. Ursolic acid, betulinic acid MdOSC1/MdOSC3/MdOSC4, MdCYP716A175, MdMYB16 [33,35,36]
      Wax esters (C22–C44) C32, C34, farnesyl linoleate MdLACS1, MdSHN2, MdWSD1, MdLACS2, MdNAC29, MdERF72 [33,37,38]
      Aldehydes: C28–C30 C30 MdCER1, MdDEWAX [28,39]
      Ketones C29 − −

      Table 2. 

      Analysis of wax components and regulatory genes in apple.

    • Wax component Core components Regulatory genes Ref.
      Alkanes: C23–C34 (odd carbons) C27, C29, C31 CsCER1, CitKCS1/CitKCS12, CitWRKY28, CitKCS1/CitKCS12, CsMYB44, CsMYB96 [5,40,41]
      Primary alcohols: C22–C32 (even carbons) C22,C24,C30 CsKCS2/CsKCS20, CsCER4/FAR3, CsERF003, CsMYB102 [5,42]
      Fatty acids: C12–C28 C16, C18, C24, C26 CsKCS20, CitKCS1, CsKCS2/CsKCS3, CsLACS1, CsMYB7, CitNAC029 [40−42]
      Triterpenoids Lanosterol, lupenol, α-amyrin,
      β-amyrin, corbigen      		 CsMYB96, CsOSC1, CsCYP716A175, CsERF003, CsMYB30, CsSQS [42−44]
      Aldehydes: C24–C28 C26, C28 CsCER3, CsMYB102, CsCER3, MdNAC29, MdERF72 [13, 41,42]

      Table 3. 

      Analysis of wax components, functions, and regulatory genes in citrus.

    • Wax component Core components Regulatory genes Ref.
      Alcohols: C16–C32 (even carbons) C32, C30 ZmCER4, ZmKCS12 [45−47]
      Aldehydes: C24–C32 (even carbons) C32, C30 ZmEREB46, ZmGL15, ZmCER2 [48,49]
      Alkanes: C23–C32 (odd carbons) C29, C31 ZmCER1, ZmFDL1 [50,51]
      Wax esters: C32–C44 (even carbons) C36, C38 ZmWSD11, ZmGL8 [45,52]
      Fatty acids: C20–C34 (even carbons) C24:0, C26:0, C28:0 ZmKCS3/ZmKCS19, ZmGPAT5 [47,50,53]
      Sterols: C27–C29 β-sitosterol (C29:1), campesterol (C28:1), stigmasterol (C29:2) ZmSMT1, ZmCYP51 [6,45,54]
      Alkyl hydroxycinnamates (AHCs): C16–C32
      (even carbons)      		 Alkyl coumarates (C20/C22), alkyl ferulates (C22/C24) ZmFHT, ZmFAR1/4/5 [45,55,56]
      ω-Hydroxy fatty acids (ω-OHFAs): C18–C32
      (even carbons)      		 18-hydroxyoleic acid (C18:1), C24/C26 ω-OHFAs ZmGPAT5, ZmCYP86A [45,50,53]
      Alkenes: C25–C33 (odd carbons) C29:1 alkene, C31:1 alkene ZmFAD2, ZmKCS20 [46,51]

      Table 4. 

      Analysis of wax components, functions, and regulatory genes in maize.

    • Wax component Core components Regulatory genes Ref.
      Primary alcohols: C22–C34 C28, C30 OSWSL5, OsPLS4, OsWSL4, OsGL1 [57−61]
      Fatty acids: C16–C34 C26, C28, C30 OsWSL4, OsABCG9, OsPLS4, OsWR1 [58,60−62]
      Alkanes: C23–C33 C27, C29, C31 OSWSL5, OsABCG9, OsPLS4, OsCER2 [60,62−64]
      Aldehydes: C28–C34 C30 and C32 OsABCG9, OsWSL2,OsWSL4 [57,61,62]

      Table 5. 

      Analysis of wax components, functions, and regulatory genes in rice.

    • Wax component Core components Regulatory genes Ref.
      β-diketones and their derivatives β-diketones, hydroxy-β-diketones TaW1, IW1, W3/W5 [65]
      Primary alcohols: C22–C35 C20, C22, C24, C26, C28 (general);
      C31, C35 (leaf epidermis)      		 TaFAR5 [7]
      n-Alkanes: C25–C35 C33 TaCER1-1A, TaCER1-6A, TaMYB96-2D/5D, TaWSD1, TaMYB60 [4,66,67]
      Wax esters (WE): C19–C50 C44 TaMIXTA-like, TaKCS6, TaFAR [68]
      Glycerides diacylglycerol (DG): C27–53, monoacylglycerol (MG): C31–C35, triacylglycerol (TG): C29–C73 DG: C47, C45. MG: C35, C31. TG: C48 TaGPAT, TaALDH7A1, TaALDH, TaDPP1, E2.3.1.158 [67]
      (O-Acyl)-1-hydroxy fatty acids (OAHFA): C31–C52 C48 TaACOT1-2-4, TaCYP704B1/CYP86 [67]
      Fatty acids: C16–C24 C16:0, C18:0, C18:1 TaMYB30, TaKCS [69]
      Aldehydes: C28–C32 C28, C30, C32 TaCER1, TaALDH [65,67]
      Other minor components: Ceramides (Cer), cholesterols (ChE), cardiolipins (CL) Cer: C29–C48, ChE: C46, CL: C65 − [67]

      Table 6. 

      Analysis of wax components, functions, and regulatory genes in wheat.

    • Species Hormone response Major wax changes Key regulatory genes
      Arabidopsis thaliana ABA, SA, JA C29 alkane↑, drought tolerance↑ AtMYB96, AtCER1, AtWRKY70
      Tomato ETH, GA, ABA Alkanes↑, wax ester dynamic changes SlCER1, SlFIS1, SlKCS
      Apple ETH, GA, ABA Primary alcohols↑, wax ester↑, optimised hydrocarbon ratio MdERF2, MdKCS2, MdMYB96
      Citrus ABA, SA, ETH C29/C31 alkanes↑, triterpenes respond to humidity[75,77–79] CsMYB96, CsCER1, CitKCS
      Maize JA, BRs, ABA C29 alkane↑, JA-wax balance ZmGL8, ZmKCS6, ZmCER3
      Rice BRs, ABA C28/C30 primary alcohol ratio remains stable OsBZR1, OsCER2, OsWSL
      Wheat ABA C27–C33 alkanes↑, enhanced drought tolerance TaMYB96, TaCER1-6A

      Table 7. 

      Hormonal responses and primary wax changes in various species.