Ester Cross-Link Profiling of the Cutin Polymer of Wild-Type and Cutin Synthase Tomato Mutants Highlights Different Mechanisms of Polymerization1
Ester Cross-Link Profiling of the Cutin Polymer of Wild-Type and Cutin Synthase Tomato Mutants Highlights Different Mechanisms of Polymerization1
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DOI：
10.1104/pp.15.01620
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发表时间：
2015-12
期刊：
影响因子：
7.4
通讯作者：
G. Philippe;C. Gaillard;Johann Petit;Nathalie Geneix;M. Dalgalarrondo;C. Brès;J. Mauxion;R. Franke-R.-Fra
中科院分区：
文献类型：
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作者：
G. Philippe;C. Gaillard;Johann Petit;Nathalie Geneix;M. Dalgalarrondo;C. Brès;J. Mauxion;R. Franke-R.-Fra
合成酶影响番茄角质的酯交联。角质层的功能与角质层聚合物的结构密切相关。然而，这种由甘油和羟基/环氧脂肪酸组成的疏水聚酯的结构和形成尚未完全解决。一种被称为CUTIN SYNTHASE1 （CUS1）的外胞体gdsl -脂肪酶是番茄果实外果皮中角质沉积所必需的。在体外，CUS1可以催化9(10)，16-二羟基十六酸的2-单酰基甘油的自酯交换反应，9(10)，16-二羟基十六酸是番茄角质素的主要单体。该反应释放甘油，并导致形成低聚物，而仲羟基仍未酯化。为了在植物中验证这一机制，在角质中进行了甘油和羟基脂肪酸的非酯化羟基的苯醚化反应。值得注意的是，在番茄RNA干扰和甲磺酸乙酯-cus1突变体中，除了角质沉积显著减少外，二羟基六酸的中链羟基酯化也受到影响。此外，在这些突变体中，甘油的sn-1、3和sn-2位置的酯化反应受到影响，它们的角质含有更高的摩尔甘油与二羟基十六酸的比例。因此，在植物中，CUS1可以催化角质单体的伯醇和仲醇基的酯化反应，并且可能存在另一种酶促或非酶促聚合机制与CUS1催化的聚合共存。该机制对仲醇的反应效率较低，产生的聚酯分子尺寸较小。苯醚化切屑的共聚焦拉曼成像表明，在果实表面聚合是异质的。最后，通过比较影响和不影响角质层聚合的番茄突变体，我们得出结论，角质层交联水平对水渗透没有显著影响。
A Synthase impacts ester cross-links of tomato cutin. Cuticle function is closely related to the structure of the cutin polymer. However, the structure and formation of this hydrophobic polyester of glycerol and hydroxy/epoxy fatty acids has not been fully resolved. An apoplastic GDSL-lipase known as CUTIN SYNTHASE1 (CUS1) is required for cutin deposition in tomato (Solanum lycopersicum) fruit exocarp. In vitro, CUS1 catalyzes the self-transesterification of 2-monoacylglycerol of 9(10),16-dihydroxyhexadecanoic acid, the major tomato cutin monomer. This reaction releases glycerol and leads to the formation of oligomers with the secondary hydroxyl group remaining nonesterified. To check this mechanism in planta, a benzyl etherification of nonesterified hydroxyl groups of glycerol and hydroxy fatty acids was performed within cutin. Remarkably, in addition to a significant decrease in cutin deposition, mid-chain hydroxyl esterification of the dihydroxyhexadecanoic acid was affected in tomato RNA interference and ethyl methanesulfonate-cus1 mutants. Furthermore, in these mutants, the esterification of both sn-1,3 and sn-2 positions of glycerol was impacted, and their cutin contained a higher molar glycerol-to-dihydroxyhexadecanoic acid ratio. Therefore, in planta, CUS1 can catalyze the esterification of both primary and secondary alcohol groups of cutin monomers, and another enzymatic or nonenzymatic mechanism of polymerization may coexist with CUS1-catalyzed polymerization. This mechanism is poorly efficient with secondary alcohol groups and produces polyesters with lower molecular size. Confocal Raman imaging of benzyl etherified cutins showed that the polymerization is heterogenous at the fruit surface. Finally, by comparing tomato mutants either affected or not in cutin polymerization, we concluded that the level of cutin cross-linking had no significant impact on water permeance.