Schmidt Simon, Lombardi Maria, Gardiner Donald M, Ayliffe Michael, Anderson Peter A
School of Biological Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.
Theor Appl Genet. 2007 Aug;115(3):373-82. doi: 10.1007/s00122-007-0571-8. Epub 2007 May 30.
Alternative splicing is an important step in controlling gene expression and has been shown to occur for a number of plant disease resistance (R) genes. The specific biological role of alternatively spliced transcripts from most R genes is unknown, yet in two cases it is clear that functional disease resistance cannot be activated without them. We report 12 splice isoforms of the M flax rust resistance gene, a TIR-NBS-LRR class of R gene. Collectively, these isoforms are predicted to encode at least nine different polypeptide products, only one of which is a full length peptide believed to confer functional M gene-specific disease resistance. An additional intron to that previously described was found in the 5' untranslated region. Splicing of this leader intron removes an upstream ORF (muORF) sequence. In some transcripts the leader intron is retained and in this case we predict negligible translation initiation of the full length M gene-encoding ORF. The majority of the alternatively spliced isoforms of M would encode truncated TIR and TIR-NBS containing proteins. Although the role of alternative splicing and the existence and function of the products they encode is still unclear, the complexities of the splicing profile, and the 5' UTR of the M gene, are likely to serve in mechanisms to regulate R protein levels.
可变剪接是控制基因表达的重要步骤，并且已证实在许多植物抗病（R）基因中都会发生。大多数R基因的可变剪接转录本的具体生物学作用尚不清楚，但在两个案例中很明显，如果没有它们，功能性抗病性就无法激活。我们报告了M亚麻锈病抗性基因的12种剪接异构体，该基因属于TIR-NBS-LRR类R基因。总体而言，这些异构体预计至少编码九种不同的多肽产物，其中只有一种是全长肽，被认为赋予功能性M基因特异性抗病性。在5'非翻译区发现了一个比先前描述的额外内含子。该前导内含子的剪接去除了上游开放阅读框（muORF）序列。在一些转录本中，前导内含子被保留，在这种情况下，我们预测全长M基因编码开放阅读框的翻译起始可忽略不计。M基因的大多数可变剪接异构体将编码截短的含TIR和TIR-NBS的蛋白质。尽管可变剪接的作用以及它们编码的产物的存在和功能仍不清楚，但M基因剪接图谱和5'UTR区域的复杂性可能参与调节R蛋白水平的机制。
