Kakeda K, Jordan N D, Conner A, Ride J P, Franklin-Tong V E, Franklin F C
Wolfson Laboratory for Plant Molecular Biology, School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2T T, United Kingdom.
Plant Cell. 1998 Oct;10(10):1723-32. doi: 10.1105/tpc.10.10.1723.
The self-incompatibility response involves S allele-specific recognition between stigmatic S proteins and incompatible pollen. This response results in pollen inhibition. Defining the amino acid residues within the stigmatic S proteins that participate in S allele-specific inhibition of incompatible pollen is essential for the elucidation of the molecular basis of the self-incompatibility response. We have constructed mutant derivatives of the S1 protein from Papaver rhoeas by using site-directed mutagenesis and have tested their biological activity. This has enabled us to identify amino acid residues in the stigmatic S proteins of P. rhoeas that are required for S-specific inhibition of incompatible pollen. We report here the identification of several amino acid residues in the predicted hydrophilic loop 6 of the P. rhoeas stigmatic S1 protein that are involved in the inhibition of S1 pollen. Mutation of the only hypervariable amino acid, which is situated in this loop, resulted in the complete loss of ability of the S protein to inhibit S1 pollen. This clearly demonstrates that this residue plays a crucial role in pollen recognition and may also participate in defining allelic specificity. We have also established the importance of highly conserved amino acids adjacent to this hypervariable site. Our studies demonstrate that both variable and conserved amino acids in the region of the S protein corresponding to surface loop 6 are key elements that play a role in the recognition and inhibition of incompatible pollen in the pollen-pistil self-incompatibility reaction.
自交不亲和反应涉及柱头S蛋白与不亲和花粉之间的S等位基因特异性识别。这种反应导致花粉受抑制。确定柱头S蛋白中参与对不亲和花粉进行S等位基因特异性抑制的氨基酸残基，对于阐明自交不亲和反应的分子基础至关重要。我们通过定点诱变构建了罂粟S1蛋白的突变衍生物，并测试了它们的生物学活性。这使我们能够鉴定出罂粟柱头S蛋白中对不亲和花粉进行S特异性抑制所必需的氨基酸残基。我们在此报告，在罂粟柱头S1蛋白预测的亲水性环6中鉴定出了几个参与抑制S1花粉的氨基酸残基。位于该环中的唯一高变氨基酸发生突变，导致S蛋白抑制S1花粉的能力完全丧失。这清楚地表明该残基在花粉识别中起关键作用，并且可能也参与确定等位基因特异性。我们还确定了该高变位点附近高度保守氨基酸的重要性。我们的研究表明，S蛋白中与表面环6相对应区域的可变和保守氨基酸都是在花粉 - 雌蕊自交不亲和反应中参与识别和抑制不亲和花粉的关键元件。
