Ethylene-Mediated Programmed Cell Death during Maize Endosperm Development of Wild-Type and shrunken2 Genotypes

Abstract

We characterized the progression of programmed cell death during maize (Zea mays L.) endosperm development of starchy (Su; wild-type) and shrunken2 (sh2) genotypes and tested the involvement of ethylene in mediating this process. Histological and viability staining demonstrated that endosperm cell death was initiated earlier and progressed more rapidly in sh2 endosperm compared with Su endosperm. lnternucleosomal DNA fragmentation accompanied endosperm cell death and occurred more extensively in sh2 endosperm. 1 -Aminocyclopropane-1 -carboxylic acid levels peaked approximately 16 d after pollination (dap) in Su endosperm and gradually decreased during subsequent development, whereas two large 1 -aminocyclopropane-1 -carboxylic acid peaks were observed in sh2 endosperm, the first between 16 and 20 dap and the second at 36 dap. Ethylene levels were elevated in sh2 kernels compared with Su kernels, with an initial peak 20 dap approximately 3-fold higher than in Su kernels and a second peak 36 dap approximately 5-fold higher than that in Su kernels. Ethylene treatment of Su kernels resulted in earlier and more extensive endosperm cell death and DNA fragmentation. Aminoethoxyvinylglycine treatment of sh2 kernels reduced the extent of DNA fragmentation. We conclude that ethylene is involved in triggering programmed cell death in developing maize endosperm and is responsible for the aberrant phenotype of sh2 kernels.

Integrated Proteomic and Cytological Study of Rice Endosperms at the Storage Phase

“…5 Previous studies of maize and barley have revealed that starch first is deposited in the central endosperm and then spreads toward the periphery during development, 6,39 and endosperm cell death closely follows the pattern of starch deposition in maize. 6 We revealed that the developing rice endosperm displays a pattern of starch accumulation and cell death similar to that in barley and maize. This finding suggests that a common position cue may specify the fate of starchy endosperm cells during development, at least in rice, maize, and barley.…”

“…To assess the endosperm cell viability, cross sections located at the longitudinal median of the endosperm were stained by Evans blue as described previously. 6 At least 20 caryopses were observed at each stage.…”

“…Evans-blue stain, which stains senescent or dead cells with lost integrity of plasma membranes, 6,24 showed only a few such cells in endosperm at 12 DAF (Figure 1b). The stained region appeared in the center of the TER at 15 DAF and extended outward from the center with TER enlargement at 18 DAF.…”

Coordinate involvement of cysteine protease and nuclease in the executive phase of plant apoptosis

“…Although some plant PCD programs induce chromatin condensation and fragmentation of nuclear DNA into a nucleosomal ladder [18][19][20][21], little is known about intracellular components and mechanisms involved in these events in plants. In animal cells, each apoptotic endonuclease such as CAD/DFF40, endoG and DNase II is solely capable of inducing DNA laddering and/or chromatin condensation [10][11][12][13]15].…”

“…Several apoptogenic effectors, such as caspases (cysteine proteases) [9][10][11][12], CAD/DFF40 (caspase-activated DNase/40 kDa DNA fragmentation factor) [9][10][11][12], endoG (mitochondrial endonuclease G) [13], DNase I [14], DNase II [15], AIF (apoptosis-inducing factor) [16] and Acinus (apoptosis chromatin condensation inducer in the nucleus) [17], have been implicated in mediating these nuclear disintegration processes using a cell-free system. In plants, chromatin condensation and DNA laddering are induced during PCD in response to biotic/abiotic stresses and developmental factors [4,6,[18][19][20][21][22]. However, only limited information is available about plant effectors, especially those involved in the executive phase of plant PCD.…”