ORIGINAL ARTICLE Study on programmed cell death and dynamic changes of starch accumulation in pericarp cells of Triticum aestivum L.* Zhuqing Zhou & Likai Wang & Jiwei Li & Xuefang Song & Chaonan Yang Received: 17 March 2009 / Accepted: 27 April 2009 / Published online: 20 May 2009 # Springer-Verlag 2009 Abstract Features of programmed cell death (PCD) and dynamic changes of starch accumulation in developing pericarp cells of wheat (Triticum aestivum L.) were observed and analyzed by periodic acid–Schiff/toluidine blue O double staining, fluorescence staining, terminal deoxynucleotidyl transferase-mediated fluorescein deoxy- uridine triphosphate nick-end labeling (TUNEL) and transmission electron microscopy. The results showed that cellular organelles were orderly disintegrated. TUNEL- positive nuclei were detected at 0 day after flowering (DAF), whereas nuclei showed significant features of degradation at 2 DAF, such as chromatin condensation, nuclei condensation, and nuclei deformation. Then, hetero- chromatin gradually disappeared and the cellular nucleus was completely degraded. The mitochondria degradation and vacuolation also were detected at 15 DAF. These results indicated that the development of pericarp cells was a typical process of PCD. However, the PCD in pericarp cells had their own characteristics: PCD started early and lasted for a considerable time. In the delayed process of PCD, starch granules were synthesized, deposited, and degraded temporarily in amyloplasts or chloroplasts. The delay of PCD in pericarp cells may be due to sufficient photosynthetic assimilates and energy supply. Besides, normal mitochondria were required for pericarp cells to survive. Pericarp cells contained only compound starch granules. Starch was massively synthesized from 0 to 11 DAF, but it was rapidly degraded after 11 DAF. Therefore, apart from protection, pericarp cells played essential roles in starch synthesis, storage, and degradation, as well as nutrient transportation. Keywords Pericarp cells . Programmed cell death (PCD) . Starch accumulation . Wheat (Triticum aestivum L.) Abbreviations DAF day after flowering DBF days before flowering HR hypersensitivity reaction NSGA numbers of starch granules in one amyloplast NAC numbers of amyloplasts in one cell PCD programmed cell death TUNEL terminal deoxynucleotidyl transferase-mediated fluorescein deoxyuridine triphosphate nick-end labeling Introduction Programmed cell death (PCD), a genetically regulated process of cell suicide, is central to the development, homeostasis, and integrity of multicellular organisms (Ameisen 2002). The PCD of animal and plant cells have many different features. In plant cells, it is accompanied by increased chromatic agglutination, vacuolation, and orderly degradation of cell inclusions. In some cases, DNA fragmentation and cysteine proteases activities are also detected (Otsuki et al. 2003; Gaffal et al. 2007; Mea et al. 2007). Many examples of PCD exist in the plants, such as root cap abscission, aerenchyma formation, differentiation of tracheary elements, leaf senescence, and hypersensitivity reaction (Pennell and Chris 1997; Jones 2001). However, Protoplasma (2009) 236:49–58 DOI 10.1007/s00709-009-0046-7 Zhuqing Zhou and Likai Wang contributed equally to this work. Z. Zhou (*) : L. Wang : J. Li : X. Song : C. Yang Laboratory of Cell Biology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China e-mail: zhouzhuqing@mail.hzau.edu.cn