Patel M, Jung S, Moore K, Powell G, Ainsworth C, Abbott A
Department of Genetics and Biochemistry, Clemson University, 122 Long Hall, Clemson, SC 29634-0324, USA.
Theor Appl Genet. 2004 May;108(8):1492-502. doi: 10.1007/s00122-004-1590-3. Epub 2004 Feb 14.
A high-oleate trait in the cultivated peanut ( Arachis hypogaea L.) was reported to rely on the allelic composition of the two homeologous, microsomal oleoyl-PC desaturase genes ( ahFAD2A or ahFAD2B). The enzyme activity of either ahFAD2A or ahFAD2B is sufficient for a normal oleate phenotype, and a significant reduction in the levels of ahFAD2B and a mutation in ahFAD2A were reported to be responsible for the high-oleate phenotype in one chemically induced mutant (M2-225) and one derived from a naturally occurring (8-2122) mutant. Here, we report an insertion of the same miniature inverted-repeat transposable element (MITE) in the ahFAD2B gene in another chemically induced mutant (Mycogen-Flavo) and the previously characterized M2-225 mutant. In both cases, this MITE insertion in ahFAD2B causes a frameshift, resulting in a putatively truncated protein sequence in both mutants. The insertion of this MITE in ahFAD2B, in addition to the point mutation in ahFAD2A, appears to be the cause of the high-oleate phenotype in Mycogen-Flavo and M2-225 mutants. Utilizing sequences of the MITE, we developed a DNA marker strategy to differentiate the two insertion-containing mutants from the normal oleate peanut variety (AT-108) and the naturally occurring, high-oleate mutant 8-2122. Reverse transcript-PCR/differential digestion results reveal the expression of both ahFAD2A and ahFAD2B genes in Mycogen-Flavo mutant. This result is in contrast to the observation that ahFAD2B transcripts are greatly reduced in the M2-225 mutant having the MITE insertion further 3' in ahFAD2B gene.
据报道，栽培花生（Arachis hypogaea L.）中的高油酸性状依赖于两个同源的微粒体油酰-PC去饱和酶基因（ahFAD2A或ahFAD2B）的等位基因组成。ahFAD2A或ahFAD2B的酶活性足以产生正常的油酸表型，据报道，在一个化学诱导突变体（M2-225）和一个天然突变体（8-2122）衍生的突变体中，ahFAD2B水平的显著降低和ahFAD2A中的突变是高油酸表型的原因。在此，我们报道了在另一个化学诱导突变体（Mycogen-Flavo）和先前鉴定的M2-225突变体的ahFAD2B基因中插入了相同的微型反向重复转座元件（MITE）。在这两种情况下，ahFAD2B中的这种MITE插入都会导致移码，从而在两个突变体中产生推定的截短蛋白序列。除了ahFAD2A中的点突变外，ahFAD2B中这种MITE的插入似乎是Mycogen-Flavo和M2-225突变体中高油酸表型的原因。利用MITE的序列，我们开发了一种DNA标记策略，以区分这两个含有插入的突变体与正常油酸花生品种（AT-108）和天然存在的高油酸突变体8-2122。逆转录-PCR/差异消化结果显示Mycogen-Flavo突变体中ahFAD2A和ahFAD2B基因均有表达。这一结果与在M2-225突变体中观察到的结果相反，在M2-225突变体中，ahFAD2B基因中3'端更远位置有MITE插入，ahFAD2B转录本大大减少。
