Characterization of programmed cell death in the endosperm cells of tomato seed: two distinct death programs

Abstract

Programmed cell death (PCD) is a requisite, genetically controlled process in plants resulting in the death of particular cells and tissues and the recycling of the cellular constituents back to the organism. PCD in the lateral and micropylar endosperm cells during and following germination of tomato ( Solanum lycopersicum L.) seeds was characterized by transmission electron microscopy, by terminal d-UTP nick-end labelling of nuclei, and agarose gel electrophoretic analysis of genomic DNA. Postgerminative cells of lateral and micropylar endosperm displayed morphologies and terminal d-UTP nick-end labelling positive nuclei consistent with PCD. PCD was not detected in the lateral endosperm in the absence of the embryo. The embryo’s effect on promoting lateral endosperm PCD could be substituted with gibberellic acid at 50 μmol/L. Micropylar endosperm cells undergo PCD irrespective of incubation with or without the embryo; gibberellic acid only hastens the onset of PCD morphology. Precursor protease vesicles, novel endoplasmic reticulum derived organelles considered markers of PCD, were observed in postgerminative lateral and micropylar endosperm cells. Internucleosomal laddering was not detected in endospermic DNA. These results suggest that a late postimbibition gibberellic acid linked mechanism promotes PCD in the lateral endosperm, whereas the promotion of PCD in the micropylar endosperm occurs early in, or prior to, imbibition.

Programmed cell death during quinoa perisperm development

“…(ii) Another type of cell death detected during quinoa seed development is that occurring in the micropylar endosperm during germination, which is also characteristic of the aleurone layer of grass endosperms, and, in general, of endosperms that store lipids and proteins. In this type, cells survive until germination, their contents become mobilized, and they die by autophagy; that is, they direct their own deterioration by secreting hydrolases that are released from the vacuole (Greenwood et al , 2005; DeBono and Greenwood, 2006). (iii) A third type of cell death, observed in the lasting layers of quinoa integuments, is also characteristic of the quinoa perisperm and grass starchy endosperm: in these tissues, death and dismantling are temporally divorced, a separation that can take years, depending on when the seeds germinate.…”

Molecular mechanisms of seed dormancy

“…2007). Also in the tomato endosperm PCD events have been observed during seed imbibition (DeBono & Greenwood 2006).…”

Ricinosomes Predict Programmed Cell Death Leading to Anther Dehiscence in Tomato

“…However, with limited exceptions (Sanders et al, 2005;Varnier et al, 2005), ultrastructural details of the progression of PCD in anther tissues other than the tapetum have been largely ignored and limited to documenting mitochondrial and nuclear changes that occur as the cells approach death. Common ultrastructural features consistent with the progression of PCD in plant cells have been provided (Gunawardena et al, 2004, and references therein;DeBono and Greenwood, 2006) and include the following: progressive condensation of chromatin with nuclear shrinkage, invagination, and lobing; aberrant morphologies and changes in electron density of mitochondria and plastids; vesiculation and vacuolization of the cytoplasm with changes in electron density of the tonoplast and cytoplasm; shrinkage of the plasma membrane from the cell wall; and vacuolar collapse. Ricinosomes may or may not be present.…”