Proteomic analysis in different development stages on SP0 generation of rice seeds after space flight

https://doi.org/10.1016/j.lssr.2020.02.001Get rights and content

Abstract

The space biological effects of plants will drive the development of aerospace science and breeding science. The aim of this study is to reveal changes in the proteome of contemporary plants at different growth and development stages after space flight of rice seeds. We carried the rice seeds (DN416) through the SJ-10 returning satellite and returned to the ground for planting to the three-leaf stage (TLP) and tillering stage (TS) after a 12.5-day orbital flight. We found that the space flight caused the rice germination rate, the TLP plant height, and the number of tillers in the TS decreased by 11.64%, 9.75%, and 9.80%, respectively. In addition, the treatment group ROS and MDA level increased in the TLP and TS. The abundance patterns of proteins in these leaves identified 214 proteins in the TLP and 286 in the TS leaves that were markedly changed. Moreover, our study identified D14 proteins that control plant height and tiller. Our results show that the space environment may affect the downstream signaling mechanism by regulating the level of ROS in the body to achieve a response to the space environment. Meanwhile, the space environment may affect the plant height and tiller of rice by altering the expression of D14 protein and hormone-regulated proteins. Our results reveal changes in the proteome of different growth stages of rice plants, and also reveal the molecular mechanism of space environment regulation of rice plant height and tiller, which provides a new direction for further understanding of space biological effects and space mutation breeding.

Introduction

The space environment has the characteristics of high vacuum, micro gravity, weak magnetic field and complex radiation, which can cause biological gene mutations and even directly affect the survival, growth, and aging of organisms (Chancellor et al., 2014). The space environment can induce a variety of biological effects. Thus, when astronauts and plant samples are exposed to the space environment, it directly threatens the health of astronauts and affects the metabolic process of plant samples (Schimmerling, 2010). The space biological effects have always been the main content of manned spaceflight. However, the lack of systematic research on space biology and the depth of research cannot meet the needs of manned space radiation hazard assessment and protection so far (La Tessa et al., 2016).

Under abiotic stress, the production of plant ROS usually increases. Plants require a certain amount of ROS to maintain vital function, and any change in their amount may affect the whole physiological process of the plant. ROS levels are maintained by a defense system called the antioxidant system, which includes both enzymatic and non-enzymatic components (Ahmad et al., 2010). Down-regulation of the antioxidant system leads to ROS-induced oxidative stress, causing harm to important cellular structures and then leading to metabolic abnormalities (Ahanger et al., 2017). Plants produce ROS as a signal molecule for stress response, which activates the signaling pathways involved in calcium and G proteins (Yan et al., 2014). In addition, ROS can also regulate the metabolic processes of plants by affecting hormone signaling. A large number of studies have been done to understand the intricate interactions between ROS and plant hormones. Due to abiotic stress, ROS levels are elevated, and the synthesis of plant hormones such as auxin (IAA), abscisic acid (ABA), and gibberellin (GAs) is regulated (Mohanta et al., 2018). ROS production can alter the auxin tendency in plants and the growth phenotype (Tognetti et al., 2010). Hormones can induce ROS production (TOGNETTI et al., 2012) and help in maintaining ROS homeostasis in plants, which indicates a close relationship between serotonin signaling and oxidative stress (Pasternak et al., 2005). However, these results are based on common biotic stresses, whether space flight, which is one of the most specific abiotic stress conditions, affects ROS levels in plants, and how ROS respond to space environmental stress needs further research.

Current research has shown that complex space environments can cause changes in plant phenotype, cell structure, genetic material, and protein (La Tessa et al., 2016). Recent studies have shown that plants can alter gene expression patterns and calcium distribution in cells to adapt to the space environment (Hasenstein et al., 2005). The expression of a great deal of genes in plants, especially stress-related genes and molecular chaperones, was significantly altered after space flight, and these changes in plants can be considered as stress responses to the space environment (Salmi and Roux, 2008). Although these studies have shown that the space environment can significantly affect the changes in gene expression levels in the plants, proteins are the performers of life activities, so it is necessary to analyze the effects of the space environment on plants from the proteome level. In addition, space flight caused changes in agronomic traits such as plant height, tiller number, ear length, grain number per ear, grain type and 1000-grain weight (Yu et al., 2007). Yu et al (2013) research also showed that the grain morphological characteristics, protein and amylose content of rice planting changed after space flight. Zhao et al (2011) study of space-borne wheat also found that space flight resulted in wheat with lower plant height, shorter ear length, fewer kernel numbers, and smaller individual plant weight and 1000-grain weight. At the same time, the agronomic traits related to plant yield changed after space flight, but the current research has observed changes in these agronomic traits and has not conducted in-depth research.

The purpose of this work is to understand protein changes in different stages of contemporary plants following the space flight of rice seeds. In order to achieve our research purposes, DN416 rice seeds were placed in the radiant metal box of the SJ-10 scientific experimental satellite, and after 12.5 days, they were brought back to the ground and planted into the TLP and the TS. First, we analyzed the effects of the space environment on agronomic traits of rice at two different growth stages and explored the changes in physiological indices related to ROS metabolism in rice leaves. Next, iTRAQ (Isobaric Tag for Relative and Absolute Quantification) technique coupled to liquid chromatography-mass spectrometry (LC-MS) analysis was applied to evaluate the changes in the proteome of rice which has two different development stages of leaves after space flight treatment. Finally, real-time quantitative PCR (RT-qPCR) was performed to assess transcript accumulation of genes encoding differentially rich proteins as demonstrated by iTRAQ.

Section snippets

Rice materials and spaceflight conditions

Rice seeds of DN416 were provided and certified by the Agricultural College of Northeast Agricultural University. In our study, the experiment was divided into two groups (treatment group and control group). The seeds of treatment group were loaded in a biological radiation box which was placed in the SJ-10 Return Satellite. The total radiation dose was 0.970 mGy (radiation equivalent = 160 μSv/d), and the gravity during flight was 104 g to 106 g. The seeds of the control group kept on the

The morphological changes of rice induced by space flight

In order to better understand the effect of space flight on rice growth and development, we analyzed some changes in agronomic traits during rice growth and development (Fig. 1). Space flight inhibits the germination rate of rice (Fig. 1A). The germination rate had decreased, with a significant difference (p < 0.01) in the space flight group compared to the control group. Next, we evaluated the effect of space flight on plant height and found that the plant height of the space flight group was

Discussion

As a special abiotic stress condition, the space environment can cause plants to change at various levels. But how plants respond and adapt to the impact of the space environment remains an open question. In this study, we systematically analyzed how rice responds to the effects of the space environment using iTRAQ technology.

Conclusions

In conclusion, we found that space flight caused a decrease in rice germination rate, plant height, tiller number, and also found that the expression trend of D14 protein was consistent with the trend of rice plant height and tiller number. Meanwhile, differentially expressed proteins are related to the calcium signaling, ABA, jasmonic acid and auxin-mediated signaling pathways. Recently accumulated evidence suggests that ROS participates in calcium signaling, ABA, jasmonic acid and

Acknowledgments

This research was supported by The National Key Research and Development Program of China (2017YFC160900), Planning Project for Space Application of China (01-1-08), National Science Foundation of China (31770918), and Strategic Priority Research Program of the Chinese Academy of Sciences (XDA04020202-12 and XDA04020412). The authors declare that there are no conflicts of interest.

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