Macroautophagy occurs in distal TMV-uninfected root tip tissue of tomato taking place systemic PCD

Abstract

Autophagy is an important mechanism for recycling cell materials upon encountering stress conditions. Our previous studies had shown that TMV infection could lead to systemic PCD in the distal uninfected tissues, including root tip and shoot tip tissues. But it is not clear whether there is autophagy in the distal apical meristem of TMV-induced plants. To better understand the autophagy process during systemic PCD, here we investigated the formation and type of autophagy in the root meristem cells occurring PCD. Transmission electron microscopy assay revealed that the autophagic structures formed by the fusion of vesicles, containing the sequestered cytoplasm, multilamellar bodies, and degraded mitochondria. In the PCD progress, many mitochondria appeared degradation with blurred inner membrane structure. And the endoplasmic reticulum was broke into small fragments. Finally, the damaged mitochodria were engulfed and degraded by the autophagosomes. These results indicated that during the systemic PCD process of root tip cells, the classical macroautophagy occurred, and the cell contents and damaged organelles (mitochondria) would be self-digested by autophagy.

Autophagy in crop plants: what's new beyond Arabidopsis ?

“…This phenotype difference was later attributed to the lack of an autophagy suppressor in the non-pathogenic mutant strain [68], suggesting that autophagy functions to inhibit pathogen-induced cell death. When tomato was infected by tobacco mosaic virus, PCD was triggered in distal non-infected areas like the root tip [128], and autophagy was also activated by virus-induced ROS production in the root tip [69]. Inhibition of autophagy led to higher ROS accumulation, suggesting that autophagy contributes to balancing ROS levels and maintaining cell survival [69].…”

Autophagy-Mediated Regulation of Different Meristems in Plants

“…When plants suffer from nutrient starvation, the number of autophagosomes increases in the elongation and differentiation regions, and numerous autophagosomes appear in plant cells near the apical meristem [ 95 ]. In addition, the canonical traits of the plant-type autophagosomes-autolysosomes pathway was observed in the root tip cells that received systemic PCD induced by TMV (tobacco mosaic virus) local infection for cell contents removal and recovery [ 96 ]. ATG genes are required for autophagy in root tip cells.…”

Destroy to create

“…Also the third contribution, by Zhou et al (2017), in the current issue, deals with a therapeutic activation of cellular dismantling, so called systemic programmed cell death. This phenomenon can be observed in root tips of Solanacean plants that have been infected by the Tobacco Mosaic Virus.…”