蕨类植物紫萁绒毡层细胞凋亡的细胞学特征(英文)

Cytological Features of the Tapetal Cells during Apoptosis in the Fern Osmunda japonica Thunb.

绒毡层凋亡过程是小孢子发生中的重要事件,以往的研究主要集中在被子植物,蕨类植物尚未见此方面的报道。该研究首次采用透射电镜和免疫荧光技术对蕨类植物紫萁(Osmunda japonica Thunb.)绒毡层细胞凋亡的细胞学过程进行了观察,以明确紫萁绒毡层细胞的发育类型和凋亡特征,为蕨类植物绒毡层细胞凋亡的深入研究以及孢子发育研究提供依据。结果显示:(1)紫萁的绒毡层属于复合型,即外层绒毡层为分泌型,该层细胞发育过程中液泡化,营养物质被吸收;内层绒毡层为原生质团型,经历了细胞凋亡的过程。(2)绒毡层内层细胞在凋亡过程中细胞壁和细胞膜降解,细胞质浓缩且空泡化;细胞核内陷、变形,染色质浓缩凝聚,形成多数小核仁,DAPI荧光由强变弱;线粒体、质体、内质网、高尔基体等细胞器逐渐退化,液泡中多包含纤维状物、絮状物、黑色嗜锇颗粒和小囊泡等;出现多泡体、多膜体和细胞质凋亡小体,上述特征与种子植物绒毡层凋亡特征基本一致。(3)与种子植物相比,紫萁绒毡层的细胞凋亡开始得早,在整个凋亡过程中没有核凋亡小体的产生;除了产生孢粉素外,绒毡层细胞内产生了大量的丝状物质、絮状物质和电子染色暗的颗粒物,这些物质可能用于形成蕨类植物的孢子周壁。

The process of the tapetal apoptosis is a key event in microsporogenesis.Previous studies have mainly focused on angiosperms,but ferns have not reported this aspect.The cytological features of the tapetal cells during apoptosis of Osmunda japonica was studied using transmission electron microscopy(TEM)and immunofluorescence technology.The main aim of this paper is to clarify the development type and apoptosis characteristics of tapetal cells of O.japonica.It provides a basis for the further study of tapetum cell apoptosis and spore development of ferns.The results showed that:(1)the structure of tapetum in Osmunda was of the mixed type.The outer layer of the tapetum was of the secretion type,and the inner layer of the tapetum was of plasmodium type.(2)The plasmodium tapetum underwent apoptosis during development.The cell wall and plasmalemma degenerated and the cytoplasm became dense and gradually vacuolated.The nuclei were collapsed and deformed.The chromatin condenses and small nucleoli were formed.The DAPI fluorescence staining became weak gradually.Organelles of mitochondria,plastids,endoplasmic reticulum,Golgi bodies gradually degenerated.The vacuoles contained fibrous,flocculent,dark osmiophilic granules and some small vesicles.Multi-vesicle bodies and multi-membrane bodies and apoptosis bodies occurred in the tapetal cells.(3)In contrast to seed plant,apoptosis of Osmunda started earlier than in seed plants;no nucleus apoptosis bodies occured during apoptosis.Besides sporopollenin,the tapetal cells also produced the fibrous,flocculent,dark osmiophilic granules during apoptosis.The materials were considered to form perispore of ferns.This paper provides a scientific basis for the further study of apoptosis of tapetal cells and spore development in ferns.