同形化型 自家不和合性에 관한 硏究動向 Ⅱ. 配偶體型 自家不和合性에 관한 遺傳分析 및 分子的 硏究

Research trend on homomorphic self-incompatibility Ⅱ. Genetic analysis and molecular research on gametophytic self-incompatibility

In gametophytic self-incompatibility, pollen tubes expressing S-alleles identical to those expressed in the style cease growth in the upper third of the style. The S-allele products of pollen and discriminate between self and cross-pollen. S-allele-associated pistil proteins(S-glycoproteins) have been identified in many Solanaceae. The sequences of a number of Solanaceous S-glycoprotein have been deduced from the corressponding cDNA sequences and compared their primary structure between them. The biological function of S-glycoproteins in the self-incompatibility interactions has not been demonstrated. S-glycoproteins corresponding to the most S-alleles isolated from style extracts of Nicotiana, Petunia, Solanum has a ribonuclease(RNase) activity. But the arrest of pollen tube growth was not simply explained by RNase action, and transcription and glycosylation process is necessary for the expression of self-incompatibility, plural genes or action sites may be involved in an S-gene. There are some unresolved question in RNase hypothesis ; How can be explain S-allele specificity? What is substrate of RNase? What is self-incompatibility related substance in pollen side against style side? Anyhow, at the moment, differences between gametophytic and sporophytic systems are clear, and we are inevitably believe that plants having different structure of flower have obtained respective systems to secure the genetic heteroveneity in the course of evolution.