Luu D T, Qin X, Morse D, Cappadocia M
Biology Department, University of Montreal, Quebec, Canada.
Nature. 2000 Oct 5;407(6804):649-51. doi: 10.1038/35036623.
Many flowering plants avoid inbreeding through a genetic mechanism termed self-incompatibility. An extremely polymorphic S-locus controls the gametophytic self-incompatibility system that causes pollen rejection (that is, active arrest of pollen tube growth inside the style) when an S-allele carried by haploid pollen matches one of the S-alleles present in the diploid style. The only known product of the S-locus is an S-RNase expressed in the mature style. The pollen component to this cell-cell recognition system is unknown and current models propose that it either acts as a gatekeeper allowing only its cognate S-RNase to enter the pollen tube, or as an inhibitor of non-cognate S-RNases. In the latter case, all S-RNases are presumed to enter pollen tubes; thus, the two models make diametrically opposed predictions concerning the entry of S-RNases into compatible pollen. Here we use immunocytochemical labelling of pollen tubes growing in styles to show accumulation of an S-RNase in the cytoplasm of all pollen-tube haplotypes, thus providing experimental support for the inhibitor model.
许多开花植物通过一种称为自交不亲和的遗传机制来避免近亲繁殖。一个高度多态的S位点控制着配子体自交不亲和系统，当单倍体花粉携带的S等位基因与二倍体花柱中存在的一个S等位基因相匹配时，该系统会导致花粉排斥（即花柱内花粉管生长的主动停滞）。S位点唯一已知的产物是在成熟花柱中表达的S-RNase。这个细胞间识别系统的花粉成分尚不清楚，目前的模型提出它要么作为一个守门员，只允许其同源的S-RNase进入花粉管，要么作为非同源S-RNase的抑制剂。在后一种情况下，所有的S-RNase都被假定进入花粉管；因此，这两种模型对S-RNase进入相容花粉的情况做出了截然相反的预测。在这里，我们使用在花柱中生长的花粉管的免疫细胞化学标记来显示所有花粉管单倍型的细胞质中都有S-RNase的积累，从而为抑制剂模型提供了实验支持。
