Autophagy Increases Zinc Bioavailability to Avoid Light-Mediated Reactive Oxygen Species Production under Zinc Deficiency

Abstract

Zinc (Zn) is an essential micronutrient for plant growth. Accordingly, Zn deficiency (2Zn) in agricultural fields is a serious problem, especially in developing regions. Autophagy, a major intracellular degradation system in eukaryotes, plays important roles in nutrient recycling under nitrogen and carbon starvation. However, the relationship between autophagy and deficiencies of other essential elements remains poorly understood, especially in plants. In this study, we focused on Zn due to the property that within cells most Zn is tightly bound to proteins, which can be targets of autophagy. We found that autophagy plays a critical role during 2Zn in Arabidopsis (Arabidopsis thaliana). Autophagy-defective plants (atg mutants) failed to grow and developed accelerated chlorosis under 2Zn. As expected, 2Zn induced autophagy in wild-type plants, whereas in atg mutants, various organelle proteins accumulated to high levels. Additionally, the amount of free Zn 21 was lower in atg mutants than in control plants. Interestingly, 2Zn symptoms in atg mutants recovered under low-light, iron-limited conditions. The levels of hydroxyl radicals in chloroplasts were elevated, and the levels of superoxide were reduced in 2Zn atg mutants. These results imply that the photosynthesis-mediated Fenton-like reaction, which is responsible for the chlorotic symptom of 2Zn, is accelerated in atg mutants. Together, our data indicate that autophagic degradation plays important functions in maintaining Zn pools to increase Zn bioavailability and maintain reactive oxygen species homeostasis under 2Zn in plants.

Comprehensive Analysis of Autophagy-Related Genes in Sweet Orange (Citrus sinensis) Highlights Their Roles in Response to Abiotic Stresses

“…Most ATGs were first identified and functionally characterized by mutagenesis studies in yeast [2]. More than 30 ATGs have now been identified in yeast, and 23, including ATG1-10, [12][13][14][16][17][18]20,27,29,31,TOR,VPS15,and VPS34, are considered to be the core ATGs participating in autophagy [3,4]. In Arabidopsis, around 40 homologues to these core ATGs have been identified, except for ATG14, 17,27,29, and 31 with no homologues [1,3].…”

“…Under heat stress, atg mutants of Arabidopsis displayed visibly impaired pollen development (including atg2-1, atg5-1, atg7-2, and atg10-1) [29] or enhanced growth inhibition (including atg2-1, atg5-1, atg12ab, and atg18a-2) [30]. Recently, Shinozaki et al proved that autophagy played important role in maintaining zinc bioavailability to avoid ROS accumulation under zinc deficiency in Arabidopsis [31]. Moreover, the potential roles of autophagy in waterlogging and excess aluminum and copper stresses were also reported [13,32,33].…”

White Oak (Quercus Fabri Hance) Regenerated Stump Sprouts Show Few Symptom of Senescence During 40 Years’growth in the Natural Forest

“…During cell senescence, macromolecules tend to catabolize rather than synthesize, thus nutrient will be transferred to healthy cells (Avila-Ospina et al 2014;Qi et al 2020aQi et al ,2020bShinozaki et al 2020). For example, during bamboo shoot postharvest stage, pathways including autophagy, fatty acid degradation and amino acid metabolism upregulated, accompanied by organism senescence (Li et al 2019).…”

Zinc and Autophagy in Age-Related Macular Degeneration

“…Starvation is usually due to lack of certain nutrients, such as carbon/glucose or nitrogen, but Kawamata et al were the first to show that zinc deficiency can also be an autophagy trigger in yeast [68,69]. On the other hand, Shinozaki et al recently showed that autophagy maintained zinc pools increased zinc bioavailability and retained ROS homeostasis under zinc deficiency in plants [70]. These cases are not directly associated with the main subject of this review, but they show that autophagy, which is considered as an evolutionary conserved process, may be regulated by zinc and vice versa-zinc homeostasis can be regulated by autophagy.…”