Allelic diversification at the wx locus in landraces of Asian rice
Allelic diversification at the wx locus in landraces of Asian rice
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DOI：
10.1007/s00122-008-0729-z
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发表时间：
2008-05-01
影响因子：
5.4
通讯作者：
Sano, Y.
中科院分区：
文献类型：
--
作者：
Mikami, I.;Uwatoko, N.;Sano, Y.
为了检查亚洲水稻 (Oryza sativa) 地方品种直链淀粉水平的连续变化，在近等基因系 (NIL) 中研究了 wx 基因座的五个假定等位基因（Wx(a)、Wx(in)、Wx(b)、Wx(op) 和 wx）。 NIL 中表观直链淀粉水平为 0.5% 至 29.9%，与 Wx 基因产物、颗粒结合淀粉合酶 (GBSS) 以及每毫克淀粉颗粒的酶活性呈正相关。只有不透明 (Wxop) 种质的 GBSS 酶活性降低到其他种质的一半。对含有 5 个不同等位基因的 18 个种质的 Wx 基因的核苷酸序列进行了比较。每个 Wx 等位基因都有一个独特的替换、移码或剪接供体位点突变，表明这些核苷酸变化可以反映在表型改变中。使用 Wx 基因构建的分子系统发育树表明 ssp。粳稻形成一个独特的进化枝，而 ssp。籼稻与野生祖先一起形成不同的进化枝。出乎意料的是，160（来自台湾的籼稻）的wx等位基因加入了粳稻谱系；然而，使用两个台湾品种的连锁基因进行比较表明，wx 基因是从粳稻到籼稻的基因流的产物。因此，粳稻谱系经常包括Wx(in)、W-xb和wx，而在其他谱系中也发现了Wx(a)和Wx(op)，强烈表明两个亚种分化后发生了等位基因多样化。目前的结果与各种地方品种中具有农艺价值的基因的维持有关。
To examine continuous variation of amylose levels in Asian rice (Oryza sativa) landraces, the five putative alleles (Wx(a), Wx(in), Wx(b), Wx(op), and wx) at the wx locus were investigated in near-isogenic lines (NILs). Apparent amylose levels ranged from 0.5 to 29.9% in the NILs, showing a positive relation with the levels of Wx gene product, granule-bound starch synthase (GBSS) as well as the enzymatic activity per milligram starch granule. Only opaque (Wxop) accessions had an enzymatic activity per GBSS that was reduced to half the level of the others. Nucleotide sequences in the Wx gene were compared among 18 accessions harboring the five different alleles. Each of the Wx alleles had a unique replacement, frame-shift or splice donor site mutation, suggesting that these nucleotide changes could be reflected in phenotype alterations. A molecular phylogenetic tree constructed using the Wx gene indicated that ssp. japonica forms a distinct clade, whereas ssp. indica forms different clades together with the wild progenitor. Unexpectedly, the wx allele of 160 (indica from Taiwan) joined the japonica lineage; however, comparisons using linked genes for two Taiwanese accessions revealed that the wx gene was the product of gene flow from japonica to indica. Therefore, the japonica lineage frequently included Wx(in), W-xb and wx, while Wx(a) and Wx(op) were found in the other lineages, strongly suggesting that allelic diversification occurred after divergence of the two subspecies. The present results were discussed in relation to the maintenance of agronomically valuable genes in various landraces.