Programmed-cell-death events during tapetum development of angiosperms

Abstract

Summary. Programmed-cell-death events in the tapetum of two angiosperms (Lobivia rauschii Zecher and Tillandsia albida Mez et Purpus) are described by ultrastructural methods. Tapetum degradation appears to be a type of programmed cell death, with the cellular remnants necessary for pollen development, acting as products of holocrine secretion. Diagnostic features of apoptosis during tapetum development are: general shrinkage of the whole cell and the nuclei; condensation of the chromatin at the periphery of the internal nuclear membrane; the enlargement of the endoplasmicreticulum cisternae to circumscribe portions of the cytoplasm; the persistence of mitochondria together with microfilament bundles until the last stages of tapetal degeneration.

PERSISTENT TAPETAL CELL1Encodes a PHD-Finger Protein That Is Required for Tapetal Cell Death and Pollen Development in Rice

“…At stage 8, the wild-type rice anther initiates an apoptosis-like cell death in the tapetum, displaying typical apoptotic hallmarks including cell shrinkage and fragmentation of chromatin DNA (Papini et al, 1999;Li et al, 2006). However, chromatin condensation, as indicated by TUNEL analysis, does not occur in the ptc1 tapetum (Fig.…”

“…The tapetum, the innermost cell layer of the anther wall, plays a crucial role in regulating programmed anther development, microspore/pollen formation, and pollen wall formation (Li et al, 2006;Parish and Li, 2010). Tapetal cell development and differentiation are critical for the early events in male reproduction, including meiosis; however, during late pollen development, tapetal degeneration, triggered by an apoptosis-like process, is also vital for viable pollen formation (Papini et al, 1999;Varnier et al, 2005;Li et al, 2006;Aya et al, 2009). Currently, although several genes encoding putative transcription factors have been reported to be associated with tapetal function and degeneration, such as Arabidopsis (Arabidopsis thaliana) MYB33/MYB65 (Millar and Gubler, 2005), DYSFUNCTIONAL TAPETUM1 (DYT1; Zhang et al, 2006), ABORTED MICROSPORE (AMS; Sorensen et al, 2003;Xu et al, 2010), and MALE STERILITY1 (MS1; Wilson et al, 2001;Ito and Shinozaki, 2002) and rice (Oryza sativa) GAMYB (Kaneko et al, 2004;Aya et al, 2009;Liu et al, 2010), UNDEVELOPED TAPETUM1 (UDT1; Jung et al, 2005), TAPETUM DE-GENERATION RETARDATION (TDR; Li et al, 2006), and MADS3 (Hu et al, 2011), their detailed functional roles in regulating tapetal PCD during anther development are unclear.…”

The unusual tegumental tissues of the Lunaria annua (Brassicaceae) seed: A developmental study using light and electron microscopy

“…The many ribosomes, both free and associated within the ER, are likely involved in producing lytic enzymes. The dead cells often showed traces of partially lysed, osmiophilic cytoplasm and nuclei, hallmarks of PCD in plants (Brighigna et al, 2006;Papini et al, 1999Papini et al, , 2010cPapini et al, , 2011. At maturity, these dead cells are characterized by their walls, which possess a loose and filamentous matrix.…”

Ultrastructure of autophagy in plant cells

“…Later on these plastids fully degenerate and are hardly recognizable. 48,67 Plastids in tapetum cells of Lobivia rauschii show several concentric double-membrane structures, and many electron-dense plastoglobules. 67 No vesicles leaving the organelle and no role of autophagy have as yet been described during the degradation of these types of plastids.…”