Culm development in grasses can be controlled by both miR156 and cytokinin. However, the crosstalk between the miR156-SPL module and the cytokinin metabolic pathway remains largely unknown. Here, we found CYTOKININ OXIDASE/DEHYDROGENASE4 (PvCKX4) plays a negative regulatory role in culm development of the bioenergy grass Panicum virgatum (switchgrass). Overexpression of PvCKX4 in switchgrass reduced the internode diameter and length without affecting tiller number. Interestingly, we also found that PvCKX4 was always upregulated in miR156 overexpressing (miR156(OE)) transgenic switchgrass lines. Additionally, upregulation of either miR156 or PvCKX4 in switchgrass reduced the content of isopentenyl adenine (iP) without affecting trans-zeatin (tZ) accumulation. It is consistent with the evidence that the recombinant PvCKX4 protein exhibited much higher catalytic activity against iP than tZ in vitro. Furthermore, our results showed that miR156-targeted SPL2 bound directly to the promoter of PvCKX4 to repress its expression. Thus, alleviating the SPL2-mediated transcriptional repression of PvCKX4 through miR156 overexpression resulted in a significant increase in cytokinin degradation and impaired culm development in switchgrass. On the contrary, suppressing PvCKX4 in miR156(OE) transgenic plants restored iP content, internode diameter, and length to wild-type levels. Most strikingly, the double transgenic lines retained the same increased tiller numbers as the miR156OE transgenic line, which yielded more biomass than the wild type. These findings indicate that the miR156-SPL module can control culm development through transcriptional repression of PvCKX4 in switchgrass, which provides a promising target for precise design of shoot architecture to yield more biomass from grasses.

The back cover image is based on the Original Article Protein kinase MtCIPK12 modulates iron reduction in Medicago truncatula by regulating riboflavin biosynthesis by Tianzuo Wang et al., https://doi.org/10.1111/pce.14527.

This study is aimed to explore the capacity of metal nanoparticles (NPs) iron, zinc, copper and their combinations introduced in the Murashige-Skoog (MS) nutrient medium (NM) to affect the growth and development of tomato plants (Solanum lycopersicum L.). NPs were prepared by a flow-levitation method. Metal NPs were characterised by transmission and scanning electron microscopy, X-ray phase analysis. Average NPs diameters were: iron - 27.0 nm, zinc - 54.0 nm, copper - 79.0 nm. MS NM was modified by substitution of common metal sulphates by neutral metal NPs instead of salts. Tomato seedlings cultivation on NM MS with NPs instead of salts assures improved seedling parameters (root length and root activity) in comparison with plants grown on standard MS. Venice cultivar tomato seedlings grown on NM with metal NPs demonstrated an increase in: seed germination by 10-180%, root length by 10-20%, and root activity by 10 -125%. After 45 days of cultivation, tomato seedlings were transplanted in a greenhouse and were grown up to the harvest. Effects in seed germination and increase of crop mass depended on metal nature and NPs concentration.

In this study, the anatomical and ultrastructural responses of Capsicum annuum to iron nanoparticles (Fe NPs) were determined. The results showed that the bio-effects of Fe NPs on plants could be positive or negative, depending on the additive concentrations. Low concentrations of Fe NPs were found to promote plant growth. Light and electron microscope analyses showed that the Fe NPs promoted plant growth by altering the leaf organization, and increasing the chloroplast number and grana stacking, as well as regulating the development of vascular bundles. Meanwhile, it was found that the Fe NPs could be absorbed in the roots, and then transported to the central cylinder in bio-available forms, where they were translocated and utilized by the leaves and stems. In contrast, high concentrations of Fe NPs appeared to be harmful to the plants, and the majority of Fe NPs were aggregated into cell walls and transported via the apoplastic pathway in the roots, which may potentially block the transfer of iron nutrients. Taken together, the aforementioned data showed that the rational use of Fe NPs could alleviate iron deficiency, and Fe NPs could be an ideal supply for Fe 2+ ions fertilizers in agriculture.

Controlled ecological life support systems (CELSS) will be an important feature of long-duration space missions of which higher plants are one of the indispensable components. Because of its pivotal role in enabling plants to cope with environmental stress, interplant communication might have important implications for the ecological stability of such CELSS. However, the manifestations of interplant communication in microgravity conditions have yet to be fully elucidated. To address this, a well-established Arabidopsis thaliana co-culture experimental system, in which UV-C-induced airborne interplant communication is evaluated by the alleviation of transcriptional gene silencing (TGS) in bystander plants, was placed in microgravity modeled by a two-dimensional rotating clinostat. Compared with plants under normal gravity, TGS alleviation in bystander plants was inhibited in microgravity. Moreover, TGS alleviation was also prevented when plants of the pgm-1 line, which are impaired in gravity sensing, were used in either the UV-C-irradiated or bystander group. In addition to the specific TGS-loci, interplant communication-shaped genome-wide DNA methylation in bystander plants was altered under microgravity conditions. These results indicate that interplant communications might be modified in microgravity. Time course analysis showed that microgravity interfered with both the production of communicative signals in UV-C-irradiated plants and the induction of epigenetic responses in bystander plants. This was further confirmed by the experimental finding that microgravity also prevented the response of bystander plants to exogenous methyl jasmonate (JA) and methyl salicylate (SA), two well-known airborne signaling molecules, and down-regulated JA and SA biosynthesis in UV-C-irradiated plants.

Space particles have an inevitable impact on organisms during space missions; radio-adaptive response (RAR) is a critical radiation effect due to both low-dose background and sudden high-dose radiation exposure during solar storms. Although it is relevant to consider RAR within the context of microgravity, another major space environmental factor, there is no existing evidence as to its effects on RAR. In the present study, we established an experimental method for detecting the effects of gamma-irradiation on the primary root growth of Arabidopsis thaliana, in which RAR of root growth was significantly induced by several dose combinations. Microgravity was simulated using a two-dimensional rotation clinostat. It was shown that RAR of root growth was significantly inhibited under the modeled microgravity condition, and was absent in pgm-1 plants that had impaired gravity sensing in root tips. These results suggest that RAR could be modulated in microgravity. Time course analysis showed that microgravity affected either the development of radio-resistance induced by priming irradiation, or the responses of plants to challenging irradiation. After treatment with the modeled microgravity, attenuation in priming irradiation-induced expressions of DNA repair genes (AtKu70 and AtRAD54), and reduced DNA repair efficiency in response to challenging irradiation were observed. In plant roots, the polar transportation of the phytohormone auxin is regulated by gravity, and treatment with an exogenous auxin (indole-3-acetic acid) prevented the induction of RAR of root growth, suggesting that auxin might play a regulatory role in the interaction between microgravity and RAR of root growth.

One of the important questions in space biology is the mechanisms underlying plant responses to an outer space environment, i.e., how gene expression is altered in space. In this study, the transcriptome of Arabidopsis thaliana seedlings was analyzed as a part of Germany SIMBOX (science in microgravity box) spaceflight experiment on Shenzhou 8 spacecraft. This experiment involved the following treatments: spaceflight with microgravity (F μg), spaceflight with 1g centrifugal force (F 1g), and ground 1g control (G 1g). Gene chips were used to screen gene expression differences in Arabidopsis thaliana seedlings among these treatments. Microarray analysis revealed that 621 genes were differentially expressed in samples F μg vs. G 1g, 249 genes in samples F 1g vs. G 1g, and 368 genes in samples F μg vs. F 1g. Gene ontology analysis indicated that the genes were involved in metabolism of stress response, gravitropic response, and DNA damage and repair, suggesting that plants adjust these metabolic pathways to space environmental stress, microgravity, and radiation.

Objective: Construct the expression vector p1301-YO-K2-YO based on the oil body expression technology which has two oleosins flanking the KGF-2,observe whether it can improve the expression level of KGF-2 and identify its biological activity. Methods: KGF-2 core gene and Arabidopsis oleosin gene were amplified by PCR,KGF-2-oleosin fused sequence was obtained by the fusion PCR,ligated with the blank vector also has a oleosin gene( p1301-oleosin),then named it p1301-YO-K2-YO,which can be tanslated into the oleosin-KGF-2-oleosin fusion protein. Agrobacterium-mediated transformation of Arabidopsis thaliana was conducted by floral dip. The total protein of the T2 seeds were extracted for SDS-PAGE,Western blot analysis,the proliferation activity of hair follicles was tested on C57 BL /6 mice. Results: The plasmid which has two oleosins flanking the KGF-2 was successfully expressed in Arabidopsis thaliana. Western blot result shows this fusion expression strategy could be twice more higher than the single-oleosin configuration production in KGF-2 protein expression,and has a certain biological activity.

Both space radiation and microgravity have been demonstrated to have inevitable impact on living organisms during space flights and should be considered as important factors for estimating the potential health risk for astronauts. Therefore, the question whether radiation effects could be modulated by microgravity is an important aspect in such risk evaluation. Space particles at low dose and fluence rate, directly affect only a fraction of cells in the whole organism, which implement radiation-induced bystander effects (RIBE) in cellular response to space radiation exposure. The fact that all of the RIBE experiments are carried out in a normal gravity condition bring forward the need for evidence regarding the effect of microgravity on RIBE. In the present study, a two-dimensional rotation clinostat was adopted to demonstrate RIBE in microgravity conditions, in which the RIBE was assayed using an experimental system of root-localized irradiation of Arabidopsis thaliana (A. thaliana) plants. The results showed that the modeled microgravity inhibited significantly the RIBE-mediated up-regulation of expression of the AtRAD54 and AtRAD51 genes, generation of reactive oxygen species (ROS) and transcriptional activation of multicopy P35S:GUS, but made no difference to the induction of homologous recombination by RIBE, showing divergent responses of RIBE to the microgravity conditions. The time course of interaction between the modeled microgravity and RIBE was further investigated, and the results showed that the microgravity mainly modulated the processes of the generation or translocation of the bystander signal(s) in roots.

Controlled ecological life support systems provide food, air, water, and other basic living resources for crew members on long-duration spaceflight missions. Plants are an important basic requirement of these systems and their biological characteristics in space have very high research value. Based on experiments of spaceflight in Shenzhou 8 spacecraft and simulating microgravity effects on three-dimensional (3-D) clinostat, the biological characteristics of tomato’s leaf cell sub-microstructure and antioxidant enzyme activities were studied and compared in this work. Results showed that leaf cell sub-microstructure of the tomato samples experiencing spaceflight had more changes than that of the samples processed by simulated microgravity effects, and both peroxidase (POD) and superoxide dismutase (SOD) activities increase obviously in both the environments.

研究不同物质及添加量对青稞蛹虫草子实体中虫草菌素含量的影响,并对影响虫草菌素产量的培养基配方进行优化.结果表明,蔗糖、蚕蛹粉、磷酸二氢钾、链霉素分别作为碳源、氮源、无机盐和生长因子有利于青稞蛹虫草子实体虫草菌素的合成、累积,且作用显著.通过正交试验确定不同物质对青稞蛹虫草子实体中虫草菌素含量影响的主次因素为蔗糖＞蚕蛹粉＞磷酸二氢钾＞链霉索＞硫酸镁＞酵母膏,各物质最佳添加量为蔗糖30g/L,蚕蛹粉7.5 g/L,磷酸二氢钾1.0 g/L,链霉素2.0 g/L,硫酸镁1.5 g/L,酵母膏2.5 g/L.在优化配方条件下,青稞蛹虫草子实体中虫草菌素含量可达8 215 mg/kg.

MicroRNA (miRNA) is a non-coding small RNA composed of 20 to 24 nucleotides that influences plant root development. This study analyzed the miRNA expression in Arabidopsis root tip cells using Illumina sequencing and real-time PCR before (sample 0) and 15 min after (sample 15) a 3-D clinostat rotational treatment was administered. After stimulation was performed, the expression levels of seven miRNA genes, including Arabidopsis miR160, miR161, miR394, miR402, miR403, miR408, and miR823, were significantly upregulated. Illumina sequencing results also revealed two novel miRNAsthat have not been previously reported, The target genes of these miRNAs included pentatricopeptide repeat-containing protein and diadenosine tetraphosphate hydrolase. An overexpression vector of Arabidopsis miR408 was constructed and transferred to Arabidopsis plant. The roots of plants over expressing miR408 exhibited a slower reorientation upon gravistimulation in comparison with those of wild-type. This result indicate that miR408 could play a role in root gravitropic response.

School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China; Science and Technology of Human Factors Engineering Laboratory, China Astronaut Research and Training Center, Beijing 100094, China; School of Biological Science and Engineering, Hebei University of Economic and Business, Shijiazhuang 050061, Hebei Province, China; and Institute of Genetic and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China. Received 26 February 2013, accepted 16 July 2013. Published on the web 13 July 2013.

目的 筛选在航天环境下表达稳定的拟南芥幼苗内参基因.方法 “神舟”8号飞船搭载拟南芥幼苗,设置3个试验处理:1)空间飞行处理(F ug);2)空间飞行+1g离心力处理(F1g);3)地面对照(G1g).样品返回后,提取总RNA,通过实时定量RT-PCR的方法,利用geNorm软件分析8个内参基因:ACT8,EF1α,eIF4A,YLS8,UBQ5,ACT2,TIP41和UBC8.结果 三个处理中,内参基因表达的稳定性如下:TIP41=UBC＞ACT2＞UBQ5＞YLS8＞eIF4A＞EF1α ＞ACT8,其中ACT2,TIP41和UBC的M值小于0.5.结论 利用qRT-PCR分析比较太空中拟南芥幼苗基因表达差异时,ACT2,TIP41和UBC可作为内参基因.

Xu, D., Guo, S. and Liu, M. 2014. Effects of long-term simulated microgravity on tomato seedlings. Can. J. Plant Sci. 94: 273–280. Whether plants can adapt to a long-term microgravity environment is crucial to their reproduction in bioregenerative life-support systems in space. This research investigated the effects of simulated microgravity on Lycopersivon esculentum Mill. (cv. Dwarf Red-bell). Several indicators, namely germination ratio, percentage of cell membrane damage, malondialdehyde content (MDA), superoxide anion ([Formula: see text]) content, and mininucleolus, were observed 10, 20, 30, and 40 d after planting (DAP). Simulated microgravity [random positioning machine (RPM) treatment] barely had any effect on germination ratio, but it increased MDA, an index indicating membrane lipid peroxidation. Random positioning machine-treated samples had significantly higher [Formula: see text] content until 16 DAP, but these differences ceased after 21 DAP. Simulated microgravity damaged cell membranes, and the damage severity was positively related to the duration of the simulated microgravity treatment. Mininucleoli were more common in RPM-treated root tips than in the 1×g ones. In conclusion, simulated microgravity seriously disturbed tomato seedling growth by damaging cell membrane integrity, causing the accumulation of hazardous substances, and affecting the cell nucleus structure.