| Summary: | 碩士 === 中國文化大學 === 生物科技研究所 === 95 === Plant disease resistance gene (R-gene) is a very big gene family, many plant disease resistance genes and related genes have been sequenced. Most of the functional sequence have some special characteristics in their structure which can be recognized whether belong to a resistance gene.
Plant disease resistance gene that encode protein sequences containing a Nucleotide-binding site domains (NBS) and C-terminal leucine-rich repeats (LRR), NBS-LRR genes are the major class of disease resistance in flowering plants, and NBS resistance gene are subdivided into two families based on the presence or absence of an N-terminal region with homology to Drosophila Toll and human interlukin-1 receptor (TIR region), namely TIR and non-TIR genes. The non-TIR type commonly has a predicted leucine-zipper (LZ)domain or putative coiled-coil (CC) domain at N-terminal region. The non-TIR family is widely distributed in both monocotyledonous and dicotyledonous species, but not seen in gymnosperm species. wherea the TIR family appears to be restricted to dicotyledonous and gymnosperm species.The research is based on cloning the resistance gene analogs within CC(TIR) and NBS regions in the R gene of Rhododenfdrom formosanum Hemsl. and Rhododendron kanehirai Wilson gene sets and analyzing their possible relationships in structure forming between these R gene domain. The results show that there’s gene duplication in both Rhododendron formosarum Hemsl. and Rhododendron kanehirai Wilson. Tajima’s relative rate test shows that there’s evolutional branching between TIR and non-TIR.
Furthermore, selective constraint analysis proves that there’s diversity between these two types of rhododendron. However, when tested with the most suitable free-ratio, most ω is less than 1, which means the end result of cloning does not allow any substitutions to form within these conserved region in order to protect it’s function.
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