蛞形橙黃壺菌 Aurantiochytrium limacinum BL10 在固態培養條件下會分泌一種可影響阿米巴細胞分化與遷移、進而調控群落發展的外泌蛋白，其分子來源與生成機制尚未明確。本研究進一步證實，於液態培養條件下亦可偵測到與固態培養相同的主要外泌蛋白（75 kDa），且其出現時序落在對數生長中期、阿米巴細胞比例高峰之後。在透過調整培養打氣量以改變細胞型態分布，發現隨阿米巴細胞比例下降，外泌蛋白分泌量亦顯著降低，於高打氣條件下幾乎無法偵測，支持該外泌蛋白主要來自阿米巴細胞。進一步以候選基因 #3413 之 RPT1–2 區域建立多株抗體系統，於 western blot 中可同時辨識 75 kDa 之外泌蛋白及一條對應於 #3413 全長蛋白之條帶，推測該外泌蛋白為 #3413 蛋白質經分泌後由蛋白水解作用所產生之片段。
本研究首次從細胞型態與分子層級連結 BL10 主要外泌分化與遷移因子的細胞來源與生成機制，為理解其群落調控行為提供新的分子基礎。

Aurantiochytrium limacinum strain BL10 secretes an extracellular protein under solid culture conditions that regulates amoeboid cell differentiation and migration, thereby influencing colony development; however, the molecular origin and generation mechanism of this protein remain unclear. In this study, we demonstrate that the same major extracellular protein (~75 kDa) is also detectable under liquid culture conditions, appearing during the mid-logarithmic growth phase after the peak proportion of amoeboid cells. By modulating aeration rates to alter cell-type composition, we observed that a decrease in amoeboid cell abundance was accompanied by a marked reduction in extracellular protein secretion, with the protein becoming nearly undetectable under high-aeration conditions, supporting the notion that this extracellular protein is primarily derived from amoeboid cells. Furthermore, antibodies generated against the RPT1–2 region of the candidate gene #3413 simultaneously recognized the 75 kDa extracellular protein and a protein band corresponding to the full-length #3413 protein in Western blot analyses, suggesting that the extracellular protein is produced as a proteolytically processed fragment of the #3413 protein following secretion. Together, these findings provide an integrated link between cell morphology and molecular processing in BL10 and offer a new molecular basis for understanding colony-level regulation mediated by extracellular proteins.

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