Abstract: In order to explore the function of GhDMT9 gene and understand the role of DNA methyltransferase in plant epigenetics and its mechanism of action, this paper cloned the GhDMT9 gene from Gossypium hirsutum L. TM-1 by PCR and constructed the pYL156:GhDMT9 VIGS silencing vector to infect cotton and PBI121:GhDMT9 overexpression vector to infect Arabidopsis thaliana.  The results of bioinformatics analysis showed that: The GhDMT9 protein with a relative molecular mass was 57 691.44 kDa, an isoelectric point was 5.45, and a total average hydrophilicity was -0.359.  GhDMT9 protein was an acidic stable with certain hydrophilic ability. It was not a secreted protein and could not migrate in cells.  There was no transmembrane domain. Secondary structure predictions contained alpha helix (29.61%), random coiling (45.29%), extended chain (19.22%) and beta-turn (5.88%). Drought and salt stress treatment of VIGS silencing GhDMT9 gene in cotton seedlings showed significant phenotypic differences. The expression pattern analysis by real-time PCR showed that the transcription level of GhDMT9 was significantly lower in the cotton infected with pYL156:GhDMT9 compared with the control. The Arabidopsis thaliana T3 seedlings overexpressing the GhDMT9 gene in drought and salt treatment showed water loss, yellowing and weak growth compared with wild-type. The cotton seedlings  silenced the GhDMT9 gene  reduced salt tolerance compared to the control. Arabidopsis thaliana overexpressing the GhDMT9 gene reduced salt tolerance compared to wild-type. Above results showed GhDMT9 gene played an important role in response to stress, which layed the foundation for further research on the stress resistance mechanism of cotton and mining functional genes.

Key words: Gossypium hirsutum L., GhDMT9, bioinformatics analysis, VIGS silencing；over-expression

摘要： 为探究GhDMT9基因的功能，深入了解DNA甲基转移酶在植物表观遗传方面的作用及其作用机制，利用PCR技术从陆地棉TM-1中克隆GhDMT9基因，构建pYL156:GhDMT9 VIGS沉默载体并侵染棉花；构建PBI121:GhDMT9过表达载体转染拟南芥。生物信息学分析结果为：GhDMT9蛋白质相对分子质量为57 691.44 kDa，等电点为5.45，总平均亲水性是-0.359，不存在跨膜结构域。GhDMT9是一种具有亲水能力的酸性稳定蛋白，不是分泌型蛋白，不能在细胞中发生迁移。二级结构预测显示含有α螺旋（29.61％）、无规则卷曲（45.29％）、延伸链（19.22％）、β-转角（5.88％）。干旱和盐胁迫处理VIGS沉默GhDMT9基因的棉花幼苗出现明显的表型差异。实时荧光定量PCR的表达模式分析结果表明：干旱和盐胁迫处理pYL156:GhDMT9侵染过的棉花与对照相比，GhDMT9的转录水平明显降低。干旱和盐处理转GhDMT9基因的拟南芥T3代幼苗叶片失水、发黄、长势较弱。棉花幼苗沉默GhDMT9基因后与对照相比耐盐性降低，过表达GhDMT9基因的拟南芥与野生型的拟南芥相比耐盐性降低。上述结果表明GhDMT9基因在棉花响应胁迫过程中发挥重要作用，为进一步研究棉花的抗逆机制，挖掘功能基因奠定基础。

关键词: 陆地棉, GhDMT9, 生物信息学分析, VIGS沉默, 超表达