Population genetics and molecular evolution in the TIR-NBS-LRR family of the Rhododendron hormosanum Hemsl.

• Main Authors: Chiun-Jr Hwang, 黃群智
• Other Authors: Shih-Ying Hwang,Ph.D.
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/14020863151758669772

碩士 === 中國文化大學 === 生物科技研究所 === 97 === The objectives of this research were to clone the resistance gene analogs within TIR-NBS-LRR regions of the Rhododendron formosanum Hemsl., and to analyze the positive selection of R gene and its relationships among the population genetics and molecular evolution. A nuclear intron DNA sequence “LEAFY” gene was used as a background gene due to unaffected by positive selection. When the populations were encountered positive selection, R gene and pathogen are either co-evoluted or diversed between populations under the demography phylogeny conditions, causing the analysis differences. The results show that birth-and-death evolution was occurred in TIR-NBS-LRR gene, resulting in different haplotypes of R. formosanum. Analyzing these haplotypes of R and LEAFY genes, several unique DNA sequences of genes were found and distributed in the ten populations, indicating that intensive gene migration was interflew between the populations of R. formosanum. Furthemore, the ω values of lineages in the R. formosanum populations were calculated using the free-ratio model of PAML program. One hundred and three out of 223 lineages were greater than one, among them, 90 and 14 ω values were higher than 700 and 999, respectively. These resutls demonstrate that the TIR-NBS-LRR domains in disease resistance genes of R. formosanum populations were favored by positive selection, which may increase adaptation of the populations from low to medium altitudes in Taiwan.