Ramos M Laura, Fleming Geraldine, Chu Ye, Akiyama Yukio, Gallo Maria, Ozias-Akins Peggy
Department of Horticulture, University of Georgia Tifton Campus, Tifton, GA, 31793, USA.
Mol Genet Genomics. 2006 Jun;275(6):578-92. doi: 10.1007/s00438-006-0114-z. Epub 2006 Apr 14.
Comparative genomic and cDNA sequence analysis of ara h 2, a major peanut allergen, and a related conglutin ara h 6 were performed in Arachis hypogaea L. and its putative progenitors, Arachis duranensis and Arachis ipaensis. The complete identity between sequences encoding Ara h 2 isoforms demonstrated that these are homeologous genes and represent orthologs from diploid ancestors. Three copies of ara h 6 were identified in A. hypogaea, one of them located in the A-genome and the other two in the B-genome. Expression analysis showed higher levels of ara h 2 transcripts compared with ara h 6. Dual-labeled genomic in situ hybridization permitted identification of two subgenomes, each of which contained one pair of ara h 2-ara h 6 signals localized by fluorescence in situ hybridization. Characterization of genomic clones showed close genetic linkage between Ara h 2.02 and one copy of ara h 6 in the B-genome. The physical linkage may have arisen by tandem duplication and divergence of an ancestral gene. A gene duplication event specific to the B-genome progenitor has resulted in ara h 6 paralogs. These data provide further evidence for progenitor relationships and genomic organization of the conglutin gene family in the genus Arachis and could contribute to the development of a hypoallergenic peanut.
对花生主要过敏原ara h 2以及相关凝集素ara h 6在花生（Arachis hypogaea L.）及其假定祖先种Arachis duranensis和Arachis ipaensis中进行了比较基因组和cDNA序列分析。编码Ara h 2亚型的序列之间完全相同，表明这些是同源基因，代表来自二倍体祖先的直系同源基因。在花生中鉴定出三个ara h 6拷贝，其中一个位于A基因组，另外两个位于B基因组。表达分析表明，与ara h 6相比，ara h 2转录本水平更高。双标记基因组原位杂交能够鉴定出两个亚基因组，每个亚基因组都包含一对通过荧光原位杂交定位的ara h 2-ara h 6信号。基因组克隆的特征表明，Ara h 2.02与B基因组中的一个ara h 6拷贝之间存在紧密的遗传连锁。这种物理连锁可能是由一个祖先基因的串联重复和分化产生的。B基因组祖先特有的基因重复事件导致了ara h 6旁系同源基因的产生。这些数据为花生属中凝集素基因家族的祖先关系和基因组组织提供了进一步的证据，并可能有助于开发低过敏性花生。
