中国农业科学 ›› 2016, Vol. 49 ›› Issue (10): 1936-1945.doi: 10.3864/j.issn.0578-1752.2016.10.010

• 园艺 • 上一篇    下一篇

三种类型柑橘成熟果实表面蜡质分析

王金秋,何义仲,徐坤洋,罗 怿,盛 玲,罗 焘,刘 欢,程运江   

  1. 华中农业大学园艺林学学院/农业部华中地区园艺作物生物学与种质创制重点实验室/园艺植物生物学教育部重点实验室,武汉 430070
  • 收稿日期:2015-11-04 出版日期:2016-05-16 发布日期:2016-05-16
  • 通讯作者: 程运江,Tel:027-87281796;E-mail:yjcheng@mail.hzau.edu.cn
  • 作者简介:王金秋,E-mail:shiyuejq023@163.com
  • 基金资助:
    国家“十二五”科技支撑计划(2015BAD16B06)、国家现代农业产业技术体系建设专项(CARS-27)、国家公益性行业科研专项(201303093)、华中农业大学自主创新基金

Characterization of Mature Fruit Surface Waxes of Three Cultivated Citrus Species

WANG Jin-qiu, HE Yi-zhong, XU Kun-yang, LUO Yi, SHENG Ling, LUO Tao, LIU Huan, CHENG Yun-jiang   

  1. College of Horticulture and Forestry, Huazhong Agricultural University/Key Laboratory of Horticultural Crop Biology and Genetic Improvement (Central Region), Ministry of Agriculture/Key Laboratory of Horticultural Plant Biology, Ministry of Education, Wuhan 430070
  • Received:2015-11-04 Online:2016-05-16 Published:2016-05-16

摘要: 【目的】分析中国主栽柑橘类型(‘鄂柑一号’椪柑(Citrus reticulata Blanco cv.Ponkan)、尤力克柠檬(C. limon cv Eureka cv. Lemon)和沙田柚(C. grandis Osbeck cv. Shatian Yu)成熟期果实表面蜡质,建立中国柑橘果实蜡质基础数据,为科学指导柑橘采后生产提供依据。【方法】以3种类型柑橘的成熟果实为材料,采用扫描电镜观察果实表面蜡质晶体结构;用GC-MS测定果实表面蜡质成分及含量;用定量PCR检测蜡质相关基因在不同类型柑橘果皮表达特性。【结果】扫描电镜结果显示沙田柚蜡质晶体呈较大的倒伏片状,椪柑片状晶体较小,柠檬介于上述两者之间。GC-MS分析表明,3种类型柑橘果实表面外蜡中脂肪族物质主要组成成分相同,分别为:脂肪醛、饱和游离脂肪酸、饱和正链烷烃和伯醇,但品种之间各组分比例及碳原子分布有一定差异。椪柑、柠檬以及沙田柚外蜡含量分别为1.1、2.2和9.3 μg·cm-2。椪柑外蜡中醛、脂肪酸、烷烃和伯醇所占比例为50%、16%、28%和6%;柠檬中各个成分比例分别为42%、30%、18%和11%;沙田柚中则分别为50%、31%、12%和7%。椪柑中26醛和28醛含量最高;柠檬中碳原子数分配比较均匀,没有绝对占主导的成分;沙田柚脂肪族物质中高碳原子数所占比例比其他柑橘类型果实蜡质中高,尤其是32酸、31和33烷烃含量很高。椪柑和柠檬总蜡含量分别为4.3和4.6 μg·cm-2。椪柑总蜡中醛、脂肪酸、烷烃和伯醇与外蜡各成分所占比例相似,分别为57%、14%、23%和4%;柠檬总蜡各成分所占比例则分别为53%、15%、19%和8%。总蜡不同种类脂肪族物质碳原子数分配与外蜡基本相同。萜类物质种类和含量在不同品种类型之间存在较大差异:柠檬中主要的三萜类成分是软木三帖酮(friedelin)、羽扇豆醇(lupeol)、α-香树精(α-amyrin)和β-香树精(β-amyrin);椪柑中主要含有后3种,没有检测到软木三帖酮;角鲨烯和法尼醇为紧皮柑橘(柚和柠檬)特有。定量表达分析表明,超长链脂肪酸辅酶A合成酶KCS6在不同柑橘类型之间的表达趋势与其对应的物质含量比较吻合,推测该基因造成了这些柑橘类型蜡质含量的差异。酰基转移酶CER2在沙田柚中表达量最高,推测该基因则导致了沙田柚中大于30碳原子数的蜡质成分在不同柑橘类型中占据最高比例。3种类型柑橘果实表面总蜡和外蜡中脂肪族物质均以醛为主,烷烃或酸次之,伯醇最少。总蜡和外蜡物质分配存在差异,其中伯醇和超长链脂肪酸在外蜡中占据比例更高,烷烃则是在外蜡中占据比例较低。萜类物质中三萜类和淄醇仅在总蜡中可以测定出,而角鲨烯和法尼醇则在外蜡和总蜡中都含有。【结论】蜡质成分在柑橘果实中受遗传背景和果皮结构共同影响。宽皮柑橘与紧皮柑橘具有不同的蜡质特征,本研究结果对宽皮柑橘和紧皮柑橘品种特异性的果蜡配方研发具有重要参考价值。

关键词: 柑橘果实, 蜡质, 扫描电镜, GC-MS, 基因表达

Abstract: 【Objective】This study is aiming at characterizing the mature fruits wax from citrus cultivated species(Citrus reticulata Blanco cv. Ponkan, C. limon cv. Eureka and C. grandis Osbeck cv. Shatian Yu) which are widespread in China, establishing the database of citrus fruits wax components, and providing important information for waxing for the specifical cultivar of citrus fruits. 【Method】Wax crystal structure of three citrus cultivars were observed by scanning electron microscopy, and cuticle thickness observed by transmission electron microscope. Subsequently, the fruits waxes of these cultivars were analyzed by gas chromatography-mass spectrometry (GC-MS). Then, the expression levels of wax associated genes were detected in different cultivars using qPCR. 【Result】 Scanning electron microscopy showed that larger and more wax platelets were deposited on the surface of tight-skin citrus Shatian Pummelo than on the loose-skin citrus Ponkan fruits, while wax platelets on lime fell in between. The total waxes of the three citrus cultivars were mostly composed of aldehydes, alkanes, fatty acids, and primary alcohols, while their proportions and carbon number distribution varied among different cultivars. The epicuticular wax concentrations in fruits of Citrus reticulata Blanco, C. limon cv Eureka and C. grandis Osbeck were 1.1, 2.2 and 9.3 μg·cm-2, respectively. The proportions of aldehydes, fatty acids, alkanes and primary alcohols in the epicuticular wax in Citrus reticulata Blanco were 50%, 16%, 28% and 6%, respectively. Their proportions in C. limon cv Eureka were 42%, 30%, 18% and 11%, respectively, while their proportions in C. grandis Osbeck were 50%, 31%, 12% and 7%, respectively. Hexacosanal (C26) and octacosanoic acid (C28) were the most abundant compounds in the epicuticular wax in Ponkan, while in Lemon, their carbon number distributed evenly. Higher carbon number aliphatic compounds were found in Shatian Pummelo, for example, dotriacontanoic acid, hentriacontane and tritriacontane were dominated. The total wax concentrations in fruits of Ponkan and Lemon were 4.3 and 4.6 μg·cm-2, respectively. The proportions of aldehydes, fatty acids, alkanes and primary alcohols in total wax in Ponkan were 57%, 14%, 23% and 4%, respectively. Their proportions in Lemon were 53%, 15%, 19% and 8%, respectively. The chain length distribution of total wax was similar with that of epicuticular wax in both of the cultivars. In addition, terpenoids showed great differences among these cultivars. The most predominant triterpenoid compounds were friedelin, lupeol, α-amyrin and β-amyrin in C. limon cv Eureka. However, there was no friedelin in total wax in Ponkan. Farnesol and squalene were exclusive in tense-skin citrus. qPCR analysis indicated that expression profile of member of beta-ketoacyl-CoA synthase family KCS6 showed a similar trend with wax amounts of the five cultivars, while member of the BAHD superfamily of acyl-transferases CER2 was expressed highest in Shatian Pummelo, which was consistent with high abundance of constituents with carbon number higher than 30. In this study, the wax of citrus fruits was mostly composed of aldehydes, followed by fatty acids or alkanes. Primary alcohols were the least predominant compounds. By comparing the distribution of wax components, it was found that, within the very-long-chain aliphatic wax components, primary alcohols and very-long-chain fatty acides tend to accumulate to higher percentages in the epicuticular layer, while alkanes occurred at lower percentages in it. With terpenoids, triterpenoids and sterols were only present in the total wax, however, squalene and farnesol were detected in both epicuticular and intracuticular wax.【Conclusion】Wax components were regulated by inheritance and peel anatomical structure synergistically. Therefore, loose-skin citrus and tight-skin citrus showed different characteristics of wax profile, which suggested that different synthetic waxes should be adopted in those two types of citrus fruits, respectively.

Key words: citrus fruits, wax, scanning electron microscope, GC-MS, expression analyses