Li Zheng-Guo, Gao Xue, Fan Jing, Yang Ying-Wu, Li Dao-Gao, Kanellis Angelos K
Genetic Engineering Research Center, Bio-Engineering College, Chongqing University, Chongqing 400044, China.
Zhi Wu Sheng Li Yu Fen Zi Sheng Wu Xue Xue Bao. 2006 Jun;32(3):381-6.
Citrus fruit is prone to develop peel pitting during development and storage, which greatly decreases its fresh market value because of the deterioration of the peel. In the present study, we have examined the effect of different temperatures (15 degrees C and 4 degrees C), waxing and mechanical damage on the changes in the activity of phenylalanine ammonia-lyase (PAL) and the incidence of peel pitting in 'Fengjie' navel orange (Citrus sinensis Osbeck) fruits. The expression levels of PAL2, PAL6 genes in the peel during the development of peel pitting have been investigated through semi-quantitative PCR method. The incidence of peel pitting was greatly enhanced by waxing and mechanical damage and was decreased in lower temperature storage (4 degrees C) (Fig.1). Waxing and mechanical damage might be the important factors inducing peel pitting and suitable low temperature could decrease the incidence of this disease. The PAL activity increased during the whole storage period in accordance with the development of this pitting (Fig.2). The expression levels of PAL2 and PAL6 genes in damaged peel were higher than those in healthy peel and the expression of PAL2 is much more higher than that of PAL6 (Figs.4 and 5). The results suggested that the enzyme activity of PAL, along with the expression of PAL2 gene is highly related to this peel pitting occurred on 'Fengjie' navel orange fruits.
柑橘类水果在发育和贮藏过程中容易出现果皮凹陷，由于果皮变质，这大大降低了其新鲜市场价值。在本研究中，我们研究了不同温度（15℃和4℃）、打蜡和机械损伤对‘奉节’脐橙（Citrus sinensis Osbeck）果实中苯丙氨酸解氨酶（PAL）活性变化和果皮凹陷发生率的影响。通过半定量PCR方法研究了果皮凹陷发育过程中果皮中PAL2、PAL6基因的表达水平。打蜡和机械损伤大大提高了果皮凹陷的发生率，而在低温贮藏（4℃）下发生率降低（图1）。打蜡和机械损伤可能是诱导果皮凹陷的重要因素，适宜的低温可降低该病的发生率。随着这种凹陷的发展，PAL活性在整个贮藏期间都有所增加（图2）。受损果皮中PAL2和PAL6基因的表达水平高于健康果皮，且PAL2的表达远高于PAL6（图4和图5）。结果表明，PAL的酶活性以及PAL2基因的表达与‘奉节’脐橙果实上发生的这种果皮凹陷高度相关。
