Functional characterization of Nicotiana benthamiana chromomethylase NbCMT2 gene in developmental programs and disease resistance

• Main Authors: Chang, Kai-Ya, 張凱雅
• Other Authors: Fu, Shih-Feng
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6w4a38

碩士 === 國立彰化師範大學 === 生物學系 === 105 === DNA methylation is a heritable epigenetic process controlling gene expression and developmental programs in various organisms. The chromomethylase (CMT) protein family is unique to plants and controls non-CpG methylation. However, the function of CMT2 genes in plants remains elusive. In this study, we isolated and characterized CMT2 gene from Nicotiana benthamiana, designated NbCMT2. We investigated the developmental expression of NbCMT2 in Nicotiana benthamiana and its roles in resistance to tomato leaf curl Taiwan virus (ToLCTV). Alignment of the NbCMT2 amino acid sequence with other plant CMTs showed conservation of bromo-adjacent-homology and methyltransferase catalytic domains. NbCMT2 has unique N-terminal extension when compared to other NbCMTs. NbCMT2 protein showed a nuclear location, which could be related to its putative cellular functions. NbCMT2 was expressed predominately in flower and other proliferating tissues such as apical shoots, and young leaves. Functional characterization was carried out by generation of transgenic N. benthamiana overexpressing NbCMT2 fused with a HA tag (HA-NbCMT2). The transgenic HA-NbCMT2 lines were characterized with increased transgene mRNA expression and accumulation of HA-fused NbCMT2 protein. Overexpressing of HA-NbCMT2 demonstrated its vital role(s) in flower development. NbCMT2 may play an essential role in flower development. In addition, transgenic N. benthamiana overexpressing NbCMT2 enhanced host resistance to ToLCTV (HA-NbCMT2). The NbCMT2 overexpressing–plants exhibited mild symptoms when infected with ToLCTV. Therefore, NbCMT2 play an essential role in flower development and resistance to ToLCTV.