固氮蓝细菌是既能进行放氧光合作用又能进行固氮作用的原核生物，其中丝状种类可以分化出特化的固氮细胞，称为异形胞。鱼腥蓝细菌PCC7120是研究异形胞分化的模式蓝细菌，其异形胞沿藻丝半规律间隔分布。HetR和PatS分别是控制异形胞分化的主调控因子和抑制性小肽，后者被称为异形胞图式的形态发生素。本实验室发现，PatS从17肽加工为C-端7肽PatS-7，再转化为抑制活性较高的6肽PatS-6和5肽PatS-5，从分化细胞扩散至其他细胞，抑制HetR与hetZ等基因启动子结合，阻止细胞分化。本项申请拟鉴定出加工PatS的蛋白酶，研究其加工识别序列、编码基因的表达和对异形胞分化的效应，并以特异识别不同小肽的单抗和荧光标记检测PatS衍生小肽沿丝体在异形胞和营养细胞的分布。其结果对于建立异形胞图式形成的分子模型、理解异形胞分化的自我免疫特征有重要价值。

Nitrogen-fixing cyanobacteria are oxygenic photosynthetic prokaryotes that perform nitrogen fixation. Some groups of filamentous species can differentiate specialized nitrogen-fixing cells, called heterocysts. Anabaena sp. PCC 7120 is the most often used research model for heterocyst differentiation. HetR and PatS are the master regulator and peptide inhibitor for heterocyst differentiation, and the latter is also called the morphogen. In my lab, the 17-aa PatS of Anabaena sp. PCC 7120 has been shown to be processed into the C-terminal heptapeptide PatS-7 and further converted into the hexapeptide PatS-6 and the pentapeptide PatS-5, the two forms of high inhibitory activities. PatS-derived peptides may diffuse to neighboring vegetative cells, inhibiting the binding of HetR to promoters of hetZ and other genes to prevent cell differentiation. This proposal describes our plan to identify the protease that processes PatS, the expression of its encoding gene and its effects on heterocyst differentiation and patterning. In addition, the distribution of PatS-derived peptides will be detected by using peptide-specific monoclonal antibodies and fluorescence labeling. The results will contribute to the establishment of a molecular model of heterocyst patterning and promote understanding of the self-immunity of heterocyst differentiation.