云南芝麻丛枝和花变叶植原体16S rRNA和rp基因序列分析

 本研究通过对表现出丛枝和花变叶症状的芝麻感病植株总DNA进行植原体16S rRNA和rp基因的PCR扩增、克隆、测序及序列分析,明确了两种病株的病原均为植原体,并将其命名为云南元谋芝麻丛枝植原体(SEWB-YNym)和云南元谋芝麻花变叶植原体(SEP-YNym)。两个株系的16S rRNA基因片段长度均为1 248 bp,并且碱基序列完全一致。通过与其他地区报道的芝麻植原体株系16S rRNA基因序列比对后发现这两个株系与来自缅甸的株系不存在位点差异,而与泰国、中国台湾、印度的株系分别存在3~6个位点差异。同时,还从两个株系中获得了长度均为1 171 bp并且碱基序列也完全一致的SEWB-YNym和SEP-YNym的rp基因序列。此rp基因序列包括全部rpl22基因(nt90-476)和部分rps3基因(nt550-1170),分别编码128和206个氨基酸。通过对16S rRNA和rp基因的序列进行同源性比对、构建系统进化树等分析,表明两个株系与候选种‘Candidatus Phytoplasma aurantifolia'相关,为16SrII-A亚组成员,并归属于植原体rp-iii亚进化支。

Sequence analysis of 16S rRNA and rp genes of sesame witches'-broom and phy-llody phytoplasma in Yunnan Province

This study confirmed that the pathogens of the sesame witches'-broom and phyllody in Yunnnan Province were both phytoplasma, and named as SEWB-YNym and SEP-YNym, respectively, based on the sequences of 16S rRNA and rp genes amplified from the total DNA of sesame disease plants. The 16S rRNA gene fragments of the two strains were both 1 248 bp in length, and the base sequences were identical. In compare with the 16S rRNA gene sequences of sesame phytoplasma strains reported from other geographical regions, the sequences of the two strains were identical with those from Myanmar, but differences on 3-6 sites with those from Thailand, Taiwan and India. The rp gene sequences of SEWB-YNym and SEP-YNym were identical with 1 171 bp in length and base sequences from the two strains. This rp gene sequence includes all rpl22 genes (nt90-476) and part of rps3 genes (nt550-1 170) which encode 128 and 206 amino acids, respectively. Through comparison of the 16S rRNA and rp gene sequences, and the construction of a phylogenetic tree, the two strains are closely related to the 'Candidatus Phytoplasma aurantifolia' in the 16SrII-A subgroup and belong to the rp-iii subclade of phytoplasma.