Takayama Seiji, Isogai Akira
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan.
J Exp Bot. 2003 Jan;54(380):149-56. doi: 10.1093/jxb/erg007.
In most self-incompatible plant species, recognition of self-pollen is controlled by a single locus, termed the S-locus. In Brassica, genetic dissection of the S-locus has revealed the presence of three highly-polymorphic genes: S-receptor kinase (SRK), S-locus protein 11 (SP11) (also known as S-locus cysteine-rich protein; SCR) and S-locus glycoprotein (SLG). SRK encodes a membrane-spanning serine/threonine kinase that determines the S-haplotype specificity of the stigma. SP11 encodes a small cysteine-rich protein that determines the S-haplotype specificity of pollen. SLG encodes a secreted form of stigma protein similar to the extracellular domain of SRK. Recent biochemical studies have revealed that SP11 functions as the sole ligand for its cognate SRK receptor complex. Their interaction induces the autophosphorylation of SRK, which is expected to trigger the signalling cascade that results in the rejection of self-pollen. This so-called ligand-receptor complex interaction and receptor activation occur in an S-haplotype-specific manner, and this specificity is almost certainly the basis for self-pollen recognition.
在大多数自交不亲和植物物种中，对自身花粉的识别由一个单一基因座控制，称为S基因座。在芸苔属植物中，对S基因座的遗传剖析揭示了三个高度多态性基因的存在：S受体激酶（SRK）、S基因座蛋白11（SP11）（也称为S基因座富含半胱氨酸蛋白；SCR）和S基因座糖蛋白（SLG）。SRK编码一种跨膜丝氨酸/苏氨酸激酶，它决定柱头的S单倍型特异性。SP11编码一种小的富含半胱氨酸的蛋白，它决定花粉的S单倍型特异性。SLG编码一种分泌形式的柱头蛋白，类似于SRK的细胞外结构域。最近的生化研究表明，SP11作为其同源SRK受体复合物的唯一配体发挥作用。它们的相互作用诱导SRK的自磷酸化，这有望触发信号级联反应，导致自身花粉被排斥。这种所谓配体-受体复合物相互作用和受体激活以S单倍型特异性方式发生，而且这种特异性几乎肯定是自身花粉识别的基础。
