Liu Yong-Zhong, Tang Peng, Tao Neng-Guo, Xu Qiang, Peng Shu-Ang, Deng Xiu-Xin, Xiang Ke-Shu, Huang Ren-Hu
National Key Laboratory of Crop Genetic Improvement, College of Horticulture and Forestry, Huazhong Agricultural University, Wuhan 430070, China.
Zhi Wu Sheng Li Yu Fen Zi Sheng Wu Xue Xue Bao. 2006 Feb;32(1):31-6.
Fruit color is one of the most important external quality traits. Mutants with different color are useful for the study of regulating mechanism of coloration progress. A novel mutant, Fengwan, derived from Fengjie72-1 navel orange (Citrus sinensis L. Osbeck), has the distinctive characteristic of the coloration delay of 30 d or so, with the change in total soluble solid (TSS) and the ratio of TSS/acidity. In order to understand the mechanism underlying the difference of coloration between the mutant and the parental variety, the chlorophyll and carotenoid contents in the peel of two cultivars at different maturation stages were analyzed. The expression of genes responsible for some carotenoid biosynthetic enzymes (phytoene synthase, phytoene desaturase, zeta-carotene desaturase, beta-lycopene cyclase, beta-carotene hydroxylase) and chlorophyllase using the RT-PCR technique were also studied. The distinct decrease of chlorophyll in the peel of Fengwan navel orange occurred from early November to late November, about three weeks later than that of its original cultivar. Obvious accumulation of carotenoid in the peel of the mutant began on Dec.12, while that of the original cultivar began on Nov. 3. Analysis of independent-samples t-test showed that the chlorophyll content of the peel of Fengwan navel orange from October to November was significantly higher, and the carotenoid content from December to January was significantly lower than that in the peel of the parental line, Fengjie72-1 navel orange. The expression of chlorophyllase gene in the peel of Fengwan navel orange reached a maximum in January and kept at a slightly lower level from October to December than that of Fengjie 72-1 orange, while the time of gene expression about some carotenoid biosynthetic enzymes reaching a maximum in the peel of the mutant were one month later than that of the original cultivar.
果实颜色是最重要的外观品质性状之一。不同颜色的突变体对于研究果实着色过程的调控机制很有用。一个新的突变体“奉晚”，源自奉节72-1脐橙（Citrus sinensis L. Osbeck），具有约30天左右的明显着色延迟特征，同时总可溶性固形物（TSS）和TSS/酸度比也发生了变化。为了了解突变体与亲本品种在着色方面差异的潜在机制，分析了两个品种在不同成熟阶段果皮中的叶绿素和类胡萝卜素含量。还利用RT-PCR技术研究了一些类胡萝卜素生物合成酶（八氢番茄红素合酶、八氢番茄红素去饱和酶、ζ-胡萝卜素去饱和酶、β-番茄红素环化酶、β-胡萝卜素羟化酶）和叶绿素酶相关基因的表达。奉晚脐橙果皮中的叶绿素在11月初至11月末明显减少，比其原始品种晚约三周。突变体果皮中类胡萝卜素的明显积累始于12月12日，而原始品种则始于11月3日。独立样本t检验分析表明，10月至11月奉晚脐橙果皮中的叶绿素含量显著更高，12月至1月其类胡萝卜素含量显著低于亲本奉节72-1脐橙果皮中的含量。奉晚脐橙果皮中叶绿素酶基因的表达在1月达到最大值，10月至12月期间比奉节72-1脐橙略低，而突变体果皮中一些类胡萝卜素生物合成酶基因表达达到最大值的时间比原始品种晚一个月。
