Principal Investigator
Researcher
Email:hqzheng@cemps.ac.cn
Personal Web:

Laboratory of Photosynthesis and Environmental Biology

2006-Present: Professor of Institute of Plant Physiology and Ecology,Shanghai Institutes for Biological Sciences（SIBS）, and Chinese Academy of Sciences (CAS), China 

2000- 2005: Associate Professor of Shanghai Institute of Plant Physiology and Ecology, SIBS, CAS, China 

2001-2002 (6 months): Visiting Scholar, University of Tuebigen, Germany 

1997- 2000: Postdoctoral Research Associate, University of Colorado, USA 

1996- 1997: Assistant Professor, Shanghai Institute of Plant Physiology, CAS, China. 

1992-1996: Ph.D. graduate studies Shanghai Institute of Plant Physiology, CAS, China 

1189-1992: M.S. graduate studies, Department of Biology, Shandong University, China  

Plants on earth have utilized gravity as the most reliable signal for morphogenesis to develop an appropriate body form for efficient life processes. Removal of the influence of gravitational acceleration by space flight causes a wide range of cellular and molecular changes in plants. Thus, it is of great interest to study plant growth in microgravity, and it is imperative that we examine whether any basic plant processes are affected by microgravity. The growth and morphogenesis of plants under microgravity conditions are greatly modified. Although as advances in plant culture technology in space, more frequent successful plant cultivation has been achieved (Sychev et al., 2008; Yano et al., 2013; Link et al., 2014), seeds developed in space are still often of lower quality and delayed development in compared with control seeds on ground (De Micco et al., 2014; Link et al., 2014).   

 In the last five years, we mainly focused on the potential important proteins and genes involved in microgravity response in two key developmental stages, seedling establishment and the phase transition, in which the plant life cycle in space can be interrupted more easily than in others also on Earth. At seedling stage, automorphogenesis often occurred and reduced successful seedling establishment in space (Zheng et al., 2007; Zheng et al., 2015; Wang et al., 2018). In opposition to automorphogenesis, gravitropism of plants on earth imposes a directional growth. Such gravitropic growth allow maximum water and nutrient uptake from the soil by roots and maximum solar energy capture by leaves. However, mechanism of plant responses to (micro)-gravity has yet been fully understood. Our studies on the proteome and transcriptome of Arabidopsis seedlings and culture cells under microgravity conditions showed that altered gravity has a significant impact on the expression of genes involved in stress responses, carbohydrate metabolism, protein synthesis, intracellular trafficking, signaling, and cell wall biosynthesis (Wang et al., 2006, Tan et al., 2010; Qi and Zheng, 2013; Zhang and Zheng, 2015; Zhang et al., 2015; Zheng et al., 2015; Wang et al., 2016; Zheng, 2018). The second stage we focused is the transition phase from vegetative to reproductive stage. On board the Chinese space lab Tiangong (TG)-2 and the Chinese recoverable Shijian (SJ)-10, Arabidopsis and rice were grown under two different photoperiod conditions. Arabidopsis completed a full life cycle in microgravity on TG-2. FLOWERING LOCUS T (FT) gene expression in both space and ground plants were observed in living time by a GFP imager (Wang et al., 2016). By comparing gene expression in space with those ground controls, a novel set of microgravity response genes, recognized mainly by quantitative differences, were identified. These results demonstrate that a new molecular plasticity in plant to adaptation to microgravity.  

In the next five years, we are going to extend the data of the microgravity response of plants obtained from the TG-2 and the SJ-10 experiments. To explore long-term space experiments from successive generations and a systematic analysis of regulatory networks at the molecular level to understand the mechanism of plant response to microgravity, we plan to use the Chinese space station (CSS) as well as the simulated microgravity machine on ground to identify particularly sensitive mechanism to the direct or indirect action of space factors in regulating phase transition and thresholds beyond which each factor can be considered a stressor due to microgravity. 

In last five years, we mainly studied plant development in space and response mechanisms of plants to (micro-)gravity. Using the Chinese satellite SJ-8, SJ-10, Chinese spacecraft Sheng Zhou (SZ)-8 and the Chinese space lab TG-2, we successfully cultured Chinese cabbage, Arabidopsis and rice in space. In addition, we also made progress on the understanding response mechanisms of plants to gravity among different organs, such as root, lateral root, shoot and its lateral organs. Molecular mechanisms involved in response to the space flight environment were also studied. The major research achievements in this field are described as follows: 

2.1 Microgravity on global gene and protein expression of plant in space: perception, response, and adaptation 

Our data presented in the proteome and transcriptome of Arabidopsis leaves and culture cells under stimulate (real) microgravity conditions showed that microgravity has a significant impact on the expression of genes and proteins involved in stress responses, carbohydrate metabolism, protein synthesis, intracellular trafficking, signaling, and cell wall biosynthesis (Wang et al., 2006, Tan et al., 2010; Qi and Zheng, 2013; Zhang and Zheng, 2015; Zhang et al., 2015; Zheng et al., 2015; Wang et al., 2016; Zheng, 2018). Among of these (micro-)gravity responsible proteome and transcriptome, we further focused on the potential important proteins and genes involved in plant response and adaptation to microgravity (Zheng et al., 2015; Wang et al., 2018). To evaluate the spaceflight-associated stress and identify molecular events important for acquired microgravity tolerance, we compared proteomic profiles of Arabidopsis thaliana callus grown under microgravity on board the Chinese spacecraft SZ-8 with callus grown under 1g centrifugation (1g control) in space. Alterations in the proteome induced by microgravity were analyzed by high performance liquid chromatography-electrospray ionization-tandem mass spectrometry with isobaric tags for relative and absolute quantitation labeling. Forty-five proteins showed significant (p<0.05) and reproducible quantitative differences in expression between the microgravity and 1g control conditions. Of these proteins, the expression level of 24 proteins was significantly up-regulated and that of 21 proteins was significantly down-regulated. The functions of these proteins were involved in a wide range of cellular processes, including general stress responses, carbohydrate metabolism, protein synthesis/degradation, intracellular trafficking/transportation, signaling, and cell wall biosynthesis. Several proteins not previously known to be involved in the response to microgravity or gravitational stimuli, such as pathogenesis-related thaumatin-like protein, leucine-rich repeat extension-like protein, and temperature-induce lipocalin, were significantly up- or downregulated by microgravity. These results imply that either the normal gravity-response signaling is affected by microgravity exposure or that microgravity might inappropriately induce altered responses to other environmental stresses. 

2.2 Molecular mechanism of gravity signal transduction in plant roots 

The annexin (ANN)2 could be interacted with auxin efflux carriers and regulate the early response of roots to the gravitational stimulation (Tan et al., 2011; Xia et al., 2017) by affecting the arrangement of actin-network in columella cells. This idea has been confirmed by the observation of a differential increase of ANN2-GFP signals in the columella cells of WT and gravity insensitive mutants pin2, pmg1 and argl, plants subject to both simulate or real microgravity. KNAT1, a homeobox family transcript factor, was found to negatively modulate root tip and the pedicel growth direction, possibly by regulating auxin redistribution after gravity signal transduction and transmission (Wei et al., 2010; Qi and Zheng, 2013). To identify novel proteins involved in the gravity signal transduction pathway, we previously carried out a comparative proteomic analysis of Arabidopsis pin2 mutant and wild type (WT) roots subjected to different gravitational conditions. These conditions included horizontal (H) and vertical (V) clinorotation, hypergravity (G) and the stationary control (S). Analysis of silver-stained two-dimensional SDS-PAGE gels revealed 28 protein spots that showed significant expression changes in altered gravity (H or G) compared to control roots (V and S). Whereas the majority of these proteins exhibited similar expression patterns in WT and pin2 roots, a significant number displayed different patterns of response between WT and pin2 roots. The latter group included 11 protein spots in the H samples and two protein spots in the G samples that exhibited an altered expression exclusively in WT but not in pin2 roots (Tan et al., 2011). One of these proteins was identified as annexin2, which was induced in the root cap columella cells under altered gravitational conditions. We further studied the expression and localization of Arabidopsis annexins under altered gravity conditions through AtANNsPro::AtANNsCDS:eGFP transgenic seedlings and reverse transcription PCR(RT-PCR). AtANN2 and AtANN4 specially expressed in root caps and AtANN4 localized in special region on endoplasmic reticulum (ER) in columella cells. Study on the response of Arabidopsis to altered gravity indicated that AtANN2 and AtANN4 could be important for roots to sense altered gravity. In addition, we found a special motif that determine AtANN4 localize on the ER membrane. These results provided us with new proofs to understand how annexins influence the response of plants to gravity.  

2.3 The space experiment on the Chinese satellite on SJ-10 

The reproductive success of plants is often dependent on their flowering time being adapted to the territorial environment, in which gravity remain constant. Whether plants can follow the same rule to determine their flowering time under microgravity in space is unknown. In our studies, a 12-day mission on orbiter Chinese recoverable satellite SJ-10 carried the long-day-flowering Arabidopsis thaliana and short-day-flowering rice (Oryza sativa) plants, and transgenic Arabidopsis plants engineered with a transgene composed of a heat shock-inducible promoter (HSP) linked to the green fluorescence protein (GFP) reporter gene and FLOWERING LOCUS T(FT) gene. The plants were used to examined FT gene expression patterns in space to address the effects of microgravity on flowering induction. In addition, application of GFP technique for FT visualization on the SJ-10 in this study is also introduced. Finally, a comprehensive analysis of global gene expression of leaves of Arabidopsis and rice grown in space under a long-day and a short-day condition, respectively, were carried out to understand effects of microgravity on photoperiodic flowering induction at molecular level. Our results showed that microgravity apparently down-regulated expression of GIGANTEA(GI), which is involved in circadian clock functions. Furthermore, possible key points of microgravity responses in the main photoperiod pathways, GI-CO-FT module in Arabidopsis or GI-Hd1-Hd3a module in rice, are also found. 

2.4 The space experiment on the Chinese space lab TG-2 

The seeds of Arabidopsis and rice were successfully germinated, grew and development under both the long-day (16h light/8h dark) and the short-day (16h light/8h dark) conditions, in space and on the ground control condition. Arabidopsis completed a full life cycle in microgravity under the long-day condition and the short-day condition transferred to the long-day condition before flowering. As we known, this is the first time, FT gene expression was observed directly in orbit by the GFP image technique (Wang et al., 2016). The results demonstrated that (1) microgravity significantly delay the photoperiod controlling floral transition. (2) Down linked images showed that expression of FT apparently up- regulated in response to microgravity in space. (3) microgravity affected the photoperiod-controlling growth of rice seedlings could be related to the enhanced guttation in space. (4) To delineate the transcriptional response mechanisms, we also carried out whole-genome microarray analysis of Arabidopsis leaves. We identified a novel set of microgravity response genes, recognized mainly by quantitative differences. These included a transcriptome signature of more pronounced proline transport in developing leaves. The further analysis provides developmental stage specific molecular resolution of different age leaves and demonstrates that a new molecular plasticity in Arabidopsis leaves to adaptation to microgravity by adjusted genome status during flowering induction in space.