[Dynamic change of ATPase activity on amyloplasts and protein bodies during the endosperm development in rice (Oryza sative L.)].

The ultracytochemical localizations of ATPase activity on amyloplasts and protein bodies were studied by using a lead precipitation technique at middle and late developmental stage of endosperm in rice (Oryza sativa L. cv. Minghui 63). The results showed that the inner and outer plasma membrane of amyloplasts, the web-like passages among starch grains and the amorphous substance surrounding the amyloplasts exhibited high ATPase activity. ATPase activity products were present on the membranes of protein body I and protein body II, and on the vacuoles and vesicle-like structures surrounding protein bodies. Active products of ATPase were also located on the plasma membrane and cell wall of starchy endosperm cells, on the cell wall, plasma membrane, nucleus and plasmodesma of aleurone and subaleurone layer cells. According to the distribution pattern of active products of ATPase, we infer that the web-like passage in amyloplast may be the transporting channel for nutrients flowing into the amyloplast. The ATPase on amyloplasts and protein bodies can supply the power for nutrients passing through the plasma membranes.

Programmed cell death in wheat during starchy endosperm development.

The starchy endosperm of wheat underwent programmed cell death (PCD) during its development. It showed a ladder of DNA fragments in multiples of 180-200 bp at specific stages when analyzed by agarose gel electrophoresis. The onset of internucleosomal fragmentation of the genome in wheat endosperm could be accelerated by ethylene. While treatment with abscisic acid (ABA) did not delay the onset of DNA fragmentation, but reduced its extent in developing wheat endosperm. During PCD, beside some ultrastructural changes common to other animal and plant apoptotic cells, the starchy endosperm cells also showed some peculiar ultrastructural features. For example, the chromatins in the nucleoplasm were densely aggregated, only a few condensed chromatins abutted onto the inner surface of the nuclear envelope; the nucleus was the first to suffer from degeneration; during nuclear disintegration a large number of organelles could still be observed in the cytoplasm; after nuclear disintegration, the cell remained alive, and synthesis and accumulation of starches and proteins were carried out as usual in the cytoplasm until the starchy endosperm cell died when it was filled with reserves; no formation of apoptotic bodies could be found and the dead starchy endosperm cell served as a reservoir. The PCD of starchy endosperm cells in wheat was a special form of PCD.

[The starchy endosperm denucleation by a process of programmed cell death during rice grain development].

The cellular ultrastructural morphology, grain filling ratio and activity of related enzymes during denucleation development stage in starchy endosperm cell of an Indica rice variety Zhongxian 8836 were observed and analyzed. The endosperm cellularization was completed at about the 3rd day after flowering (DAF). At 5 DAF a few endosperm cells initiated denucleation development. At 13 DAF almost all the starchy endosperm cells completed their denucleation. The nuclear degradation is the first stage of programmed cell death (PCD) in starchy endosperm. It occurred unsynchronously among different starchy endosperm cells. The nuclear degradation of starchy endosperm cell during denucleation development stage showed not only morphological features commonly observed in animal and plant PCD, but also some unique characteristics. Mitochondria degeneration was observed along with nuclear degradation, indicating there were interrelations between the two processes. Enzymes related to PCD, such as super-oxide dismutases (SOD) and catalase (CAT), as well as enzymes related to starch synthesis, such as ADP-glucose pyriphosphorylase (AGP), soluble starch synthase (SSS) and starch branching enzyme or Q-enzyme, showed very high activity during the denucleation development stage. Maximum grain filling rate and grain weight increase were also achieved in the denucleation developing stage of most starch endosperm cells. The denucleated cell remained alive in the developing endosperm, keeping its normal metabolisms, the synthesis and accumulation of starch and storage proteins. However, enzyme activities and grain filling rate were apparently dropped to a lower level after denucleation. The starchy endosperm cell finally completed its PCD process when it was completely filled with reserves. Evan's blue staining indicated that cell death occurred unsynchronously among the starchy endosperm cells with initiation points randomly distributed in the endosperm tissue.

Ultrastructural localization of ATPase in mature tracheary elements of rice (Oryza sativa L.) stamen.

The development of mature tracheary elements (TEs) of rice (Oryza sativa L. cv. Nongkeng 58s-SD) stamen from big-vacuole to trinucleate pollen stage was studied with lead phosphate--deposition technique. At big-vacuole pollen stage, mature TEs, both in filament and connective, were short of ATPase activity. However, ATPase activity appeared at binucleate pollen stage; in filament, one or two vascular bundle cell (s) next to TE degenerated earlier than the rest; and the plasma membrane of degenerating cell (DC) always exhibited high ATPase activity on condition that the adjoining TE was of fully stretched second wall; when the second wall only turned up far off DC, the plasma membrane of DC still showed high ATPase activity except on borderline between DC and TE; in connective at the same stage, TEs also exhibited high ATPase activity, but the vascular bundle cell(s) adjoining TEs degenerated much later than their counterparts in filament. At trinucleate pollen stage, materials, either with or without ATPase activity, were observed both in filament and connective TEs. The above results indicated that (some of the) materials in mature TEs come from filament DC.