Studies on pollen coat proteins involved in pollen-stigma interactions in Brassica sp.

植物有性生殖依赖于花粉和雌蕊之间高度特异性的相互作用。雌蕊能够识别和选择到达柱头上的遗传多样性的花粉，因此只有合适的花粉才能起受精作用。这些系统包括跨种受精障碍和种内障碍，如自交不亲和（SI），阻止自花受精。在芸苔属植物中，一个蛋白家族的污名表达成员，SLG家族，预计在这些识别系统中发挥核心作用。SRK （s -受体激酶）和SLG （s -位点糖蛋白）被证明参与了SI中自我/非自我花粉的识别。SLR1可能参与了花粉-柱头粘附的初始阶段。虽然这些家族性蛋白被认为与花粉粒上的某些成分相互作用，但这些成分的分子性质仍然难以捉摸。在本研究中，我们在PCP（花粉外壳蛋白）蛋白家族中寻找这些相互作用的分子，并成功鉴定出两个关键成分SP11和SLR1-BP。SP11编码于自交不亲和位点，属于PCP家族的一个新类别，被证明是SI的花粉决定因素。我们提出的实验证据表明，SP11作为一种自我/非自我识别标记，被SRK感知到柱头乳头细胞。SLR1- bp是PCP a类蛋白的新成员，与SLR1具有高亲和力的相互作用。虽然SLR1-BP的生物学意义尚未得到实验证实，但SLR1与SLR1-BP的相互作用有望参与花粉-柱头粘附过程。本研究鉴定的这两种花粉成分应该是理解花粉-柱头识别过程的关键分子。

Plant sexual reproduction depends on highly specific interactions between pollen and pistil. Pistils can recognize to select from the genetically diverse range of pollen arriving on the stigma so that only appropriate pollen effects fertilization. These systems include barriers to cross-species fertilization and intraspecific barriers such as self-incompatibility (SI) that prevent self-fertilization.In Brassica, stigmaticaly expressed members of a protein family, SLG family, are expected to play central roles in these recognition systems. SRK (S-receptor kinase) and SLG (S-locus glycoprotein), are shown to be involved in the recognition of self/non-self pollen in SI.SLR1 is suggested to be involved in the initial stages of pollen-stigma adhesion. Although these familial proteins are expected to interact with some components on pollen grains, the molecular nature of these components remained elusive.In this study, we searched for these interacting molecules in PCP (pollen coat protein) family of proteins and succeeded to identify two key component named SP11 and SLR1-BP.SP11, which is encoded in the self-incompatibility (S) locus and belongs to a novel class of PCP family, is tumed out to be the pollen determinant of SI.We presented experimental evidence showing that SP11 is working as a self/non-self recognition marker which is perceived by SRK on stigmatic papillar cells. SLR1-BP, which is a new member of PCP class A proteins, is interacting with SLR1 with high affinity. Although the biological signficance of SLR1-BP is as yet to be exprimentally demonstrated, the interaction between SLR1 and SLR1 -BP is expected to be involved in the pollen-stigma adhesion process. These two pollen components identified in this study should be key molecules in understanding the pollen-stigma recognition process.