Isshiki M, Nakajima M, Satoh H, Shimamoto K
Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-0101, Japan.
Plant J. 2000 Aug;23(4):451-60. doi: 10.1046/j.1365-313x.2000.00803.x.
In the endosperm of japonica rice, du-1 and du-2 mutations cause the reduction of amylose contents. It was previously shown that the Wx(b) allele of rice, which is predominantly distributed in japonica rice, has a mutation in the 5' splice site of intron 1 resulting in the creation of two weak 5' splice sites within exon 1. In du-1 and du-2 mutants, spliced Wx(b) transcripts were highly reduced, whereas the processing of transcripts derived from three other genes highly expressed in endosperm was not apparently influenced. Results of competitive RT-PCR analysis indicate that transcripts spliced at the two newly created 5' splice sites were equally affected in these two mutants. Genetic and molecular analyses of the effects of du-1 and du-2 on Wx(a) pre-mRNA with normal splice sites indicate that these two mutations do not affect the processing of Wx(a) pre-mRNA after splicing, suggesting that du-1 and du-2 are mutations of genes required for the efficient splicing of mutated Wx(b) pre-mRNA. Furthermore, du-1 and du-2 showed differential effects in endosperm and pollen. Although both mutations caused similar effects on the splicing of Wx(a) transcripts in endosperm, du-1 caused higher reduction of Wx(b) mRNA in pollen than in endosperm, while du-2 had a lesser effect in pollen than in endosperm. Based on these results, we propose that the du-1 and du-2 loci of rice encode tissue-specifically regulated splicing factors that are involved in alternative splicing of pre-mRNA in rice.
在粳稻胚乳中，du - 1和du - 2突变导致直链淀粉含量降低。先前研究表明，主要分布于粳稻中的水稻Wx(b)等位基因在第1内含子的5'剪接位点发生突变，导致外显子1内产生两个较弱的5'剪接位点。在du - 1和du - 2突变体中，剪接后的Wx(b)转录本大幅减少，而胚乳中高表达的其他三个基因的转录本加工过程未受明显影响。竞争性逆转录 - 聚合酶链反应（RT - PCR）分析结果表明，在这两个突变体中，在两个新产生的5'剪接位点进行剪接的转录本受到同等程度的影响。对du - 1和du - 2对具有正常剪接位点的Wx(a)前体mRNA影响的遗传和分子分析表明，这两个突变不影响剪接后Wx(a)前体mRNA的加工过程，这表明du - 1和du - 2是突变的Wx(b)前体mRNA有效剪接所需基因的突变。此外，du - 1和du - 2在胚乳和花粉中表现出不同的效应。尽管这两个突变对胚乳中Wx(a)转录本的剪接产生相似的影响，但du - 1导致花粉中Wx(b) mRNA的减少幅度高于胚乳，而du - 2对花粉的影响小于胚乳。基于这些结果，我们提出水稻的du - 1和du - 2位点编码组织特异性调控的剪接因子，参与水稻前体mRNA的可变剪接。
