毛竹茎秆纤维细胞发育过程中的细胞程序性死亡

利用TUNEL检测、细胞学及细胞化学方法,对毛竹茎秆纤维细胞发育过程中的细胞程序性死亡进行了研究。在次生壁形成的早期,纤维细胞出现染色质凝聚、细胞器膨胀、液泡膜解体和细胞质泡状化等典型的细胞程序性死亡形态学特征;TUNEL检测反应呈阳性,显示此时的纤维细胞核DNA发生了片段化。此时,在纤维细胞裂解的液泡膜、降解的细胞质和凝聚的染色质上具有ATPase活性。纤维细胞质的Ca^2＋水平会随着次生壁的形成而逐渐升高,随后Ca^2＋聚集成块状。在初生壁形成后期,纤维细胞染色质上的酸性磷酸酶（APase）活性增强。随着纤维次生壁的持续增厚,ATPase、酸性磷酸酶和Ca^2＋将在裂解的细胞质和凝聚的染色质上持续存在多年。结果表明,毛竹茎秆纤维细胞的次生壁形成过程是一个主动自溶的细胞程序性死亡过程。初生壁形成后期染色质上酸性磷酸酶活性增强及次生壁形成期胞质Ca^2＋的聚集,与纤维细胞的程序性死亡密切相关。ATPase,Ca^2＋和APase参与了纤维细胞程序性死亡过程中原生质体的降解。

Programmed Cell Death during Fiber Cell Development in Phyllostachys edulis (Poaceae) Culm

Programmed cell death during fiber cell development in Phyllostachys edulis culms was studied by using the TUNEL assay, and the cytological and cytochemical methods. At the early stage of secondary wall formation, the morphological features of PCD such as chromatin agglutination, organelle swelling, and the tonoplast disintegration and cytoplasm vacuolation were investigated in fiber cells. Positive signals by TUNEL assay could be also detected which evidenced the nDNA fragmentation. Mg2+-ATPase activity was examined on the cleavage tonoplast, disintegrated cytoplasm and agglutinated chromatin of fiber cells at that time. The level of Ca2+ in fiber cytoplasm would increase with secondary wall formation, and Ca2+ would be congregated densely. APase was sparsely localized on the nuclear chromatin during primary wall formation, but it was densely aggregated at the late stage. With the continual thickening of secondary wall, the cleavage cytoplasm and agglutinated chromatin with the activity of Mg2+-ATPase and APase in fiber cells were persistent for many years, and Ca2+ was also detected in these structures. The results showed that secondary wall formation of fiber in P.edulis culm was an active autophagic PCD, and the aggregation of Ca2+ in cytoplasm during secondary wall formation and APase densely localized on the nuclear chromatin during late primary wall formation, were correlated to the occurrence of fiber PCD. Mg2+-ATPase, Ca2+ and APase were all involved in the disintegration of fiber protoplast during PCD.