Cell death in seedlings of the interspecific hybrid of Nicotiana gossei and N. tabacum; possible role of knob-like bodies formed on tonoplast in vacuolar-collapse-mediated cell death

Abstract

Vacuolar collapse plays a direct role in the cell death of the interspecific hybrid of Nicotiana gossei Domin xN. tabacum L. which exhibits hybrid lethality at the seedling stage. We have previously reported that cell death in these seedlings began at the base of hypocotyls and spread throughout the plant (Mino et al. 2002). A light microscopic analysis revealed that the process involved disruption of the intra-cellular membranes, plasmolysis, and retraction of the wall of the cell in hypocotyls. A transmission electron microscopic analysis showed that there were several abnormal structures, i.e. knob-like bodies on the tonoplast and small vesicles in the cytoplasm, and the disintegration of the tonoplast, in the cells of seedlings grown at 26 degrees C. However, no such cytological defects were observed in the seedlings grown at 37 degrees C, at which temperature the expression of lethality was suppressed. The activity levels of vacuolar processing enzyme (VPE), which might be involved in the vacuolar collapse of plant cells, temporarily increased in the seedlings grown at 26 degrees C before apparent cell death proceeded, but it remained unchanged in the seedlings grown at 37 degrees C. Applications of acetyl-L: -tyrosyl-L: -valyl-L: -alanyl-L: -aspart-1-aldehyde, an inhibitor for VPE, and cycloheximide to the seedlings suppressed VPE's activities, the formation of knob-like bodies on the tonoplast, and cell death. VPE might be involved in the structural anomalies on the tonoplast which lead to cell death triggered by vacuolar collapse in hybrid seedlings.

Vacuolar processing enzyme activates programmed cell death in the apical meristem inducing loss of apical dominance

“…Accordingly, no prevention of AMS101 labelling by the caspase 3 inhibitor Ac-Asp-Glu-Val-Asp-1-aldehyde was detected (Figure 2c). VPE is a vacuolar enzyme (Hara-Nishimura & Maeshima, 2000;Hatsugai et al, 2015;Kinoshita et al, 1999), and consequently, it exhibits maximal activity at acidic pH (Figure 3a), suggesting optimal localization for activity in the cell vacuole (Hatsugai et al, 2006;Kinoshita et al, 1999;Kuroyanagi et al, 2002;Mino et al, 2007;Misas-Villamil et al, 2013;Sueldo & van der Hoorn, 2017). VPE is a legumain, a member of the cysteine proteases (reviewed by Bonneau, Ge, Drury, & Gallois, 2008;Bosch, Poulter, Perry, Wilkins, & Franklin-Tong, 2010).…”

Release of Apical Dominance in Potato Tuber Is Accompanied by Programmed Cell Death in the Apical Bud Meristem

“…Plants do possess a phylogenetically distinct family of Cys proteases, the VPEs (legumains; Hatsugai et al, 2004Hatsugai et al, , 2006Kuroyanagi et al, 2005) and serinyl aspartate-specific proteases (Coffeen and Wolpert, 2004;Piszczek and Gutman, 2007). In the process of PCD in plants, disruption of vacuoles or a change in the permeability of the tonoplast plays an essential role in the speed of death and the degree of recovery of the cell contents (Mino et al, 2007). VPEs, as well as other types of proteases (Bonneau et al, 2008;Lam, 2008;Reape and McCabe, 2008), are functionally but not structurally related to caspases (Vercammen et al, 2004;Watanabe and Lam, 2004;Bonneau et al, 2008).…”

“…A known amount of 7-amino-4-methylcoumarin was used for calibration. To confirm that the hydrolyzing activity was from VPE, 200 mM Ac-YVAD-CHO, which specifically inhibits VPE (Hatsugai et al, 2004;Mino et al, 2007), was added to the reaction mixture. Protein content was determined with the BCA Protein Assay kit (Pierce) using bovine serum albumin as the standard.…”

“…VPE activity was measured using the method reported by Mino et al (2007) with some modifications. The frozen apical meristems were homogenized in extraction buffer (50 mM sodium acetate, pH 5.5, 50 mM NaCl, 1 mM EDTA, and 100 mM dithiothreitol [DTT]) under ice-cold conditions.…”

Achievement of genetics in plant reproduction research: the past decade for the coming decade

“…Embryonic death has been found at interspecific crosses in several plant genera such as Nicotiana (Zhou et al, 1991), Gossypium (Phillips, 1977), and wheat (Zeven, 1981). Although causal genes have not been identified yet, these genes seem to involve programmed cell death, along with chromatin condensation, nuclear fragmentation and vacuolar collapse (Mino et al, 2007;Tezuka et al, 2007). In Drosophila, it has been proposed that polygene controls hybrid male sterility (Tao et al, 2003;Moehring et al, 2006).…”