Identification of coiled body-like structures in meristematic cells of Pisum sativum cotyledonary buds

This study focused on two types of nuclear bodies visible in plant cells th at were previously thought to be similar to the coiled bodies (CBs) of anim al cells: the nucleolus-associated body (NAB) and dense body (DB). We show that both NABs and DBs share common features with animal CBs: they consist of ribonucleoproteins, are silver-stainable, and lack DNA. Immunoelectron m icroscopy shows that only the NABs are rich in snRNAs and fibrillarin, two markers characteristic of animal CBs. This suggests that NABs rather than D Bs are the plant counterparts of the CBs of animal cells. These structures appear most frequently in cells blocked in G0-1, their frequency gradually declining with resumption of the cell cycle and nucleolar activity. During this reactivation period, NABs are released from the nucleolus to the nucle oplasm, suggesting that they may act as nuclear transport or sorting struct ures.