近年來對於黏菌聚集物要形成具移動能力的蛞蝓（slug）或者是進入向上延伸生長期（culmination）形成成熟的子實體的研究有了新的發現。我們經由限制酶插入突變法篩選出發育受到影響的突變株。在營養充足的環境下，隨著時間增加，會有拖曳物的出現，且拖曳物上有似水珠的滴狀物聚集；而在營養缺乏的環境下，突變株在發育早期聚集遲緩，且在發育36小時之後就會有拖曳物的形成，將蛞蝓撐離開地面。mtpA基因是單一拷貝基因，在阿米巴時期（vegetative stage）和發育早期表現量很少，直到發育12-16小時（大約是蛞蝓期）才有大量的表現之後就開始下降。經由序列比對分析，mtpA基因可轉譯出含有14個transmembrane domains 的膜上運輸蛋白(membrane transporter)。在協同發育實驗中發現，只要混合少部分野生株即可產生子實體，所以我們認為MtpA蛋白質對於細胞間訊息的產生或釋出是必須的;將90%的野生株混合10%的轉殖act15::lacZ的突變株進行發育，染色後發現突變株細胞主要分佈在孢原細胞區域，在發育後期則是分佈在子實體的上杯和下杯的部分，並能夠進入孢原細胞分化路徑，卻不參與在桿子結構的形成，由嵌合體的發育情形臆測， mtpA基因被剔除會影響桿子細胞的分化。突變株對於環境的變化很敏感，如丙酸鈉會造成其聚集能力的明顯下降而少量的氯化銨就能完全抑制其聚集，但三氮化鈉卻對其聚集能力有提升的作用。在經由流式細胞儀測定發現相較於野生株，突變株有胞內酸化的現象，或許這就是造成突變株會有延緩聚集的現象且對環境的pH值變化十分的敏感的原因。過去實驗證實PKA的活性上升會促進蛞蝓進入最後的發育，所以我們將持續表現PKA-catalytic活性的突變株rdeC (HTY217) 的mtpA基因剔除，HTY217/mtpA-雙重突變株發現雖然也能產生相似比例的孢子和桿子細胞，但在型態上和HTY217並不完全相同，所以持續表現PKA活性並不能完全彌補剔除mtpA基因所造成的缺失。結果顯示MtpA蛋白質的功能在早期細胞聚集過程可能調控胞內pH值來抵抗抑制物而在後期發育能夠藉由調控PKA的活性來調控最後的細胞分化。

By screening developmentally morphological mutants generated by the restriction enzyme-mediated integration (REMI) mutagenesis, we found a mutant that formed trails that lift the slug off substratum and with age could collect droplets of fluid along their length on bacterial lawn agar. The mutant cells were delayed to aggregate and had a defect in culmination (slugger mutant). The full-length gene was constructed from the plasmid rescued fragments and predicted to encode a membrane transporter, MtpA, containing fourteen transmembrane domains. The mtpA gene is single copy gene and the temporal expression is a very low level at vegetative stage, increases substantially about 12-16 hr and then decreases. In synergy experiments, they participated efficiently in fruiting bodies formation when developing along with wild-type cells, suggesting that MtpA affects the production or release the intracellular signal pathways. The act15::lacZ-marked mtpA- cells were excluded from the prestalk zone in slug stage and distributed over up and low cup at culmination stage, indicating that the mtpA- cells should have an inherent defect in the prestalk differentiation. The development of mtpA- cells was hypersensitive to the change of the environmental ammonia and propionate concentration but its aggregation-ability was slightly rescued by the azide. Disrupted mtpA gene leads to cytosolic acidification by FACS measurements. It is likely the reason to cause to delay to aggregate and over-sensitive to the environmental change. Knocked out mtpA gene in rapidly developing and sporogenous rdeC mutant HTY217 that lacks functional PKA regulatory and therefore has constitutive PKA catalytic activity, the phenotype of the double mutant HTY217/ mtpA- is partially like to the parental strain but is able to form spores. Our results indicate that MtpA plays as a regulator of the ammonia in the early aggregation via possibly regulating the intracellular pH and is required for the intercellular signal that controls the terminal differentiation of the prespore and prestalk cells via regulating the PKA activity.

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