Xiong Bo, Gu Xianjie, Qiu Xia, Dong Zhixiang, Ye Shuang, Sun Guochao, Huang Shengjia, Liu Xinya, Xi Lijuan, Wang Zhihui
College of Horticulture, Sichuan Agricultural University, Chengdu, Sichuan, China.
Mianyang Academy of Agricultural Sciences, Mianyang, Sichuan, China.
PLoS One. 2017 Jun 15;12(6):e0178973. doi: 10.1371/journal.pone.0178973. eCollection 2017.
Considering the known effects of xyloglucan endotransglycosylase (XET) on plant growth and development, we aimed to determine whether XETs help to regulate the growth and elongation of Huangguogan shoots and roots. We confirmed a possible role for XET during seedling etiolation. Our results revealed that the roots of etiolated seedlings (H-E) were longer than those of green seedlings (H-G). However, shoot length exhibited the opposite pattern. We also observed positive and negative effects on the xyloglucan-degrading activity of XET in the root sub-apical region and shoots of etiolated Huangguogan seedling, respectively. There was a significant down-regulation in CitXET expression in the etiolated shoots at 15 days after seed germination. On the contrary, it was significantly increased in the root sub-apical region of etiolated and multicolored seedlings at 15 days after seed germination. The XET coding sequence (i.e., CitXET) was cloned from Huangguogan seedlings using gene-specific primers. The encoded amino acid sequence was predicted by using bioinformatics-based methods. The 990-bp CitXET gene was highly homologous to other XET genes. The CitXET protein was predicted to contain 319 amino acids, with a molecular mass of 37.45 kDa and an isoelectric point of 9.05. The predicted molecular formula was C1724H2548N448O466S14, and the resulting protein included only one transmembrane structure. The CitXET secondary structure consisted of four main structures (i.e., 21% α-helix, 30.72% extended strand, 9.09% β-turn, and 39.18% random coil). Analyses involving the NCBI Conserved Domains Database (NCBI-CDD), InterPro, and ScanProsite revealed that CitXET was a member of the glycosyl hydrolase family 16 (GH16), and included the DEIDFEFLG motif. Our results indicate that the differed degrees of etiolation influenced the CitXET expression pattern and XET activity in Huangguogan seedlings. The differential changes in XET activity and CitXET expression levels in Huangguogan seedlings may influence the regulation of root and shoot development, and may be important for seedling etiolation.
考虑到木葡聚糖内转糖基酶（XET）对植物生长发育的已知影响，我们旨在确定XET是否有助于调节黄果柑嫩枝和根系的生长与伸长。我们证实了XET在幼苗黄化过程中可能发挥的作用。我们的结果显示，黄化幼苗（H-E）的根比绿色幼苗（H-G）的根长。然而，嫩枝长度呈现相反的模式。我们还分别观察到XET对黄化黄果柑幼苗根尖下区域和嫩枝中木葡聚糖降解活性的正向和负向影响。种子萌发15天后，黄化嫩枝中CitXET表达显著下调。相反，在种子萌发15天后，黄化和彩色幼苗的根尖下区域中CitXET表达显著增加。使用基因特异性引物从黄果柑幼苗中克隆了XET编码序列（即CitXET）。利用基于生物信息学的方法预测了编码的氨基酸序列。990 bp的CitXET基因与其他XET基因高度同源。预测CitXET蛋白含有319个氨基酸，分子量为37.45 kDa，等电点为9.05。预测的分子式为C1724H2548N448O466S14，所得蛋白质仅包含一个跨膜结构。CitXET二级结构由四种主要结构组成（即21%的α螺旋、30.72%的延伸链、9.09%的β转角和39.18%的无规卷曲）。涉及NCBI保守结构域数据库（NCBI-CDD）、InterPro和ScanProsite的分析表明，CitXET是糖基水解酶家族16（GH16）的成员，并包含DEIDFEFLG基序。我们的结果表明，不同程度的黄化影响了黄果柑幼苗中CitXET的表达模式和XET活性。黄果柑幼苗中XET活性和CitXET表达水平的差异变化可能影响根和嫩枝发育的调控，并且可能对幼苗黄化很重要。
