Wang Yuling, Zhang Xinfu, Yang Shaolan, Wang Caihong, Lu Guilong, Wang Ran, Yang Yingjie, Li Dingli
Qingdao Key Laboratory of Genetic Improvement and Breeding in Horticultural Plants, Department of Horticulture, Qingdao Agricultural University, Qingdao 266109, China.
Qingdao Key Laboratory of Genetic Improvement and Breeding in Horticultural Plants, Department of Horticulture, Qingdao Agricultural University, Qingdao 266109, China.
Gene. 2017 Dec 30;637:181-189. doi: 10.1016/j.gene.2017.09.056. Epub 2017 Sep 28.
Lignin, a natural macromolecular compound, plays an important role in the texture and taste of fruit. Hard end is a physiological disorder of pear fruit, in which the level of lignification in fruit tissues is dramatically elevated. Cinnamyl alcohol dehydrogenase and expansin genes (PpCAD2 and PpEXP2, respectively) exhibit higher levels of expression in 'Whangkeumbae' (Pyrus pyrifolia) pear fruit exhibiting this physiological disorder, relative to control fruit without symptoms. These genes were isolated from pear fruit and subsequently expressed in tobacco (Nicotiana tabacum) to investigate their function. Histochemical staining for lignin revealed that the degree of lignification in leaf veins and stem tissues increased in plants transformed with sense constructs and decreased in plants transformed with antisense constructs of PpCAD2. The expression of native NtCADs was also inhibited in the antisense PpCAD2 transgenic tobacco. Sense and antisense PpCAD2 transgenic tobacco exhibited an 86.7% increase and a 60% decrease in CAD activity, respectively, accompanied by a complementary response in lignin content in root tissues. The basal portion of the stem in PpEXP2 transgenic tobacco was bent and highly lignified. Additionally, the level of cellulose also increased in the stem of PpEXP2 transgenic tobacco. Collectively, these results suggested that PpCAD2 and PpEXP2 genes play a significant role in lignin accumulation in transgenic tobacco plants, and it is inferred that these two genes may also participate in the increased lignification observed in hard end pear fruit.
木质素是一种天然高分子化合物，在果实的质地和口感方面发挥着重要作用。硬端病是梨果实的一种生理病害，其中果实组织中的木质化水平显著升高。肉桂醇脱氢酶基因和扩展蛋白基因（分别为PpCAD2和PpEXP2）在表现出这种生理病害的‘黄金梨’（Pyrus pyrifolia）梨果实中的表达水平，相对于无症状的对照果实更高。这些基因从梨果实中分离出来，随后在烟草（Nicotiana tabacum）中表达以研究它们的功能。木质素的组织化学染色显示，用正义构建体转化的植株中叶脉和茎组织的木质化程度增加，而用PpCAD2反义构建体转化的植株中则降低。在反义PpCAD2转基因烟草中，天然NtCADs的表达也受到抑制。正义和反义PpCAD2转基因烟草的CAD活性分别增加了86.7%和降低了60%，同时根组织中的木质素含量呈现互补性变化。PpEXP2转基因烟草茎的基部弯曲且高度木质化。此外，PpEXP2转基因烟草茎中的纤维素水平也有所增加。总体而言，这些结果表明PpCAD2和PpEXP2基因在转基因烟草植株的木质素积累中发挥着重要作用，据此推测这两个基因可能也参与了硬端病梨果实中观察到的木质化增加过程。
