Search

Calcium (Ca

The mitogen-activated protein kinase OsMPK1 is involved in abscisic acid (ABA) biosynthesis in rice (Oryza sativa L.). However, the underlying molecular mechanisms of OsMPK1 in regulating ABA biosynthesis are poorly understood. Here, by using yeast two-hybrid assay and firefly luciferase complementary imaging assay, we show that OsMPK1 physically interact with a short-chain dehydrogenase protein OsABA2. However, OsMPK5, a homolog of OsMPK1, does not interact with OsABA2. Further, OsMPK1 can phosphorylate OsABA2S197 in vitro. Phosphorylation at the position of OsABA2S197 does not affect its subcellular localization, but enhances the stability of OsABA2 protein. We also found that OsABA2 has feedback regulation on OsMPK1 kinase activity. Further research reveals that OsMPK1 and OsABA2 coordinately regulate the biosynthesis of ABA, and phosphorylation of OsABA2 at Ser197 by OsMPK1 plays a crucial role in regulating the biosynthesis of ABA. Finally, genetic analysis showed that OsABA2 can enhance the sensitivity of rice to ABA and the tolerance of rice to drought and salt stress.

Asymmetric nucleophilic addition of 3-substituted N-Boc oxindoles to 3-bromooxindoles was designed to directly construct hetero-3,3′-bisoxindoles, with varying vicinal quaternary carbon stereocente...

Brassinosteroids (BRs) are plant steroidal phytohormones that play an important role in plant growth, stress responses, and adaptation. BIP130 is a BR-INSENSITIVE 1 (BRI1)-interacting protein, and BIP130 phosphorylation by OsMPK1 upregulates abscisic acid (ABA)-induced antioxidant defense in rice protoplasts. However, studies on BIP130-induced modulation of plant responses to salt stress are lacking. This study investigated the function of BIP130 in response to salt stress in transgenic rice (Oryza sativa L.). We assayed the relative BIP130 transcript levels in wild-type (WT) plants with NaCl treatment and observed the effects on scavenging reactive oxygen species (ROS) in transgenic plants. Changes in ABA content in transgenic plants were also analyzed. NaCl treatment upregulated relative transcript and protein levels of BIP130 in WT plants. The bip130 RNA interference (RNAi) rice mutants displayed a hypersensitive response to salt stress, while BIP130-overexpressing plants showed significant enhancement of salt tolerance, which was confirmed by changes in survival rates, antioxidant enzyme activities, H2O2 levels, and electrolyte leakage. RNA-sequencing analysis showed that BIP130 upregulates nine ABA-related genes (OsPSY2, OsNCED3, OsNCED4, OsCIPK6, OsCIPK16, OsCIPK31, OsEDL3, OsbZIP23, OsHVA22). ABA content significantly increased in BIP130-overexpressing and significantly decreased in bip130-RNAi plants. Therefore, BIP130 is involved in NaCl-induced antioxidant defense and enhances salt stress tolerance by modulating ABA biosynthesis and ROS scavenging in rice.

The bioaccumulation of cadmium (Cd) in crop and the subsequent food chain has aroused extensive concerns. However, the underlying molecular mechanisms of plant Cd tolerance remain to be clarified from the viewpoint of novel candidate genes. Here we described a highly efficient approach for preliminary identifying rice Cd-tolerant genes through the yeast-based cDNA library survival screening combined with high-throughput sequencing strategy. About 690 gene isoforms were identified as being Cd-tolerant candidates using this shotgun approach. Among the Cd-tolerant genes identified, several categories of genes such as BAX inhibitor (BI), NAC transcription factors and Rapid ALkalinization Factors (RALFs) were of particular interest, and their function of Cd tolerance was further validated via heterologous expression, which suggested that SNAC1, RALF12, OsBI-1 can confer Cd tolerance in yeast and tobacco leaves. Regarding the genes involved in ion transport, the validated Cd-tolerant heavy metal-associated domain (HMAD) isoprenylated protein HIPP42 was particularly noteworthy. Further elucidation of these genes associated with Cd tolerance in rice will benefit agricultural activities.

In rice (Oryza Sativa), Osmotic Stress/ABA-activated Protein Kinase 10 (SAPK10) has been shown to be induced by hyperosmotic stress and abscisic acid (ABA). However, the molecular function of SAPK10 and its downstream targets in ABA-induced antioxidant defense is poorly understood. Here, we identified an unknown function DUF1639 family protein, OsDUF1639.1, which interacts with SAPK10 in vitro and in vivo. OsDUF1639.1 positively regulates ABA responses in seed germination and tolerance to drought stress. We found that SAPK10 directly phosphorylates OsDUF1639.1 at Thr-80 in vitro. The transient expression analysis in combination with mutant analysis in rice protoplasts showed that Thr-80 is essential for ABA-induced stimulation of antioxidant defense by SAPK10. These results suggest that SAPK10 functions upstream of OsDUF1639.1 to regulate the activities of antioxidant enzymes, and Thr-80 phosphorylation of OsDUF1639.1 has a crucial role in ABA-induced antioxidant defense.

Abscisic acid (ABA) is a key component of many signaling networks mediating plant adaptation to various stresses. In this context, ABA-induced antioxidant defence is considered to be a main mechanism to that enhances water stress tolerance in plants. The specific details of this activation remain, however, elusive. In this work, we show that DIP1, a protein from novel R3H family, played a central role in modulating water stress tolerance in rice. OsDIP1 transcripts were induced by hydrogen peroxide (H2O2), ABA, drought (polyethylene glycol treatment), and salt stress. Overexpression of OsDIP1 in rice enhanced drought and salinity tolerance while knocking out OsDIP1 by CRISPR-Cas9 editing resulted in drought and salt sensitive phenotype. The activity and gene expression of antioxidant defence enzymes, superoxide dismutase (SOD), catalase (CAT), increased in OsDIP1-overexpressed transgenic rice plants, while the content of malondialdehyde (MDA) decreased. In contrast, the content and gene expression of SOD and CAT, decreased, and the content of MDA increased in knockout of OsDIP1 rice plants, suggesting that overexpression of OsDIP1 enhances the antioxidant capacity of rice plants. The yeast two hybrid screening test revealed that OsDIP1 interacted with ZFP36, a key zinc finger transcription factor involved in ABA-induced antioxidant defence. Moreover, OsDIP1 could modulate some key ABA-responsive genes via interacting with ZFP36. Overall, our findings indicate an important role of OsDIP1 in ABA-induced antioxidant defence signaling and adaptation to salinity and drought in rice.

Aluminum (Al) toxicity is the major limiting factor for plant production and crop yield on acid soils. Previous works revealed that ZFP36 played a key role in plant adaptation to water stress and rice blast. Here, we report another function of ZFP36, which is associated with detoxification of Al toxicity through abscisic acid (ABA)- dependent mechanism, in rice. Al exposure significantly increased ZFP36 expression level in an ABA-dependent manner. Knocking down ZFP36 triggered Al sensitivity, while overexpressing ZFP36 resulted in an increased Al tolerance. Chromatin immunoprecipitation-sequencing (ChIP-seq), yeast one-hybrid assay, and dual luciferase test revealed that a tonoplast-localized Al transporter, OsALS1, and antioxidant defense enzymes were targeted by ZFP36. Moreover, by combining yeast two-hybrid assay, bimolecular fluorescence complement (BiFC), GST pull-down and in vitro phosphorylation assay, we showed that ZFP36 could interact with and be phosphorylated by the pyruvate dehydrogenase kinase OsPDK1. A strong association was found between the expression, protein content and kinase activity of OsPDK1 with the responses to ABA and Al. Using transgenic plants, we have showed that OsPDK1 could inhibit OsALS1 expression via regulating ZFP36. Overall, our data demonstrates a new ZFP36-controlled mechanism of Al defense in rice plants, which is mediated by OsPDK1.

A highly enantioselective isocyanide-based multicomponent reaction catalyzed by a chiral N,N'-dioxide/MgII complex was reported. A wide range of substrates were tolerated in this reaction, including alkyl- and aryl-substituted isocyanides with alkylidene malonates and various phenols, affording the corresponding phenoxyimidate products in good to excellent yields (up to 94% yield) with good to excellent enantioselectivities (up to 95.5:4.5 er). A catalytic cycle and transition state were proposed to rationalize the reaction process and enantiocontrol.

Plants have evolved various strategies to sense and respond to saline environments, which severely reduce plant growth and limit agricultural productivity. Alteration to the cell wall is one strategy that helps plants adapt to salt stress. However, the physiological mechanism of how the cell wall components respond to salt stress is not fully understood. Here, we show that expression of XTH30, encoding xyloglucan endotransglucosylase-hydrolase30, is strongly up-regulated in response to salt stress in Arabidopsis. Loss-of-function of XTH30 leads to increased salt tolerance and overexpression of XTH30 results in salt hypersensitivity. XTH30 is located in the plasma membrane and is highly expressed in the root, flower, stem, and etiolated hypocotyl. The NaCl-induced increase in xyloglucan (XyG)-derived oligosaccharide (XLFG) of the wild type is partly blocked in xth30 mutants. Loss-of-function of XTH30 slows down the decrease of crystalline cellulose content and the depolymerization of microtubules caused by salt stress. Moreover, lower Na+ accumulation in shoot and lower H2O2 content are found in xth30 mutants in response to salt stress. Taken together, these results indicate that XTH30 modulates XyG side chains, altered abundance of XLFG, cellulose synthesis, and cortical microtubule stability, and negatively affecting salt tolerance., Xyloglucan endotransglucosylase-hydrolase30 modulates xyloglucan side chains by altering abundance of xyloglucan-derived oligosaccharide, negatively affecting salt tolerance.

Cadmium (Cd) is a widespread non-essential toxic heavy metal and usually arouses oxidative stress which impairs plant growth. The key lipophilic antioxidant α-tocopherol is synthesized from γ-tocopherol by γ- tocopherol-methyl-transferase (γ-TMT encoded by VTE4) in response to a variety of abiotic stresses. The main purpose of this study was to characterize the Cd-tolerant maize ZmVTE4 which was obtained through high-throughput survival screening in the presence of Cd. Further heterologous expression of a ZmVTE4 enhanced Cd tolerance in yeast as well in tobacco. Moreover, Cd treatment induced the increment of tocopherols in maize leaves. Similarly, transient overexpressing ZmVTE4 increased the content of γ-tocopherol and α-tocopherol thus enhancing the Cd tolerance in tobacco leaves. Visualized fluorescence indicated that ZmVTE4 was localized in chloroplasts, where tocopherols were synthesized. These results collectively implicated that ZmVTE4-mediated α-tocopherol generation facilitated plant tolerance to Cd.

Facing the growing high data rate and large communication capacity demands, optical communications are widely recognized to be used to implement satellite communications. For a space-based optical backbone network, an appropriately designed protocol stack is important. In this paper, we proposed a protocol stack that is suitable for a space-based optical backbone network. Following this, we then used software to simulate this stack, built a hardware platform to test it, and finally, analyzed the results. The results showed that the proposed protocol stack was well designed to provide efficient control and management of the space-based optical backbone network. It could improve management efficiency by collecting resources and automatically calculating and building route paths. It could also facilitate data forwarding in intermediate satellite nodes with limited source and power, by using an advanced orbiting systems (AOS) frame switching scheme to avoid unnecessary processes, such as unpacking, upper-layer processing and repacking for passing services. The protocol stack could also support the use of unidirectional links to improve the link resource utilization. Finally, it could also provide transparent transmission for different kinds of services.

Due to global warming and population growth, plants need to rescue themselves, especially in unfavorable environments, to fulfill food requirements because they are sessile organisms. Stress signal sensing is a crucial step that determines the appropriate response which, ultimately, determines the survival of plants. As important signaling modules in eukaryotes, plant mitogen-activated protein kinase (MAPK) cascades play a key role in regulating responses to the following four major environmental stresses: high salinity, drought, extreme temperature and insect and pathogen infections. MAPK cascades are involved in responses to these environmental stresses by regulating the expression of related genes, plant hormone production and crosstalk with other environmental stresses. In this review, we describe recent major studies investigating MAPK-mediated environmental stress responses. We also highlight the diverse function of MAPK cascades in environmental stress. These findings help us understand the regulatory network of MAPKs under environmental stress and provide another strategy to improve stress resistance in crops to ensure food security.

Drought stress seriously limits crop productivity. Although studies have been carried out, it is still largely unknown how plants respond to drought stress. Here we find that drought treatment can enhance the phosphorylation activity of brassinosteroid-signaling kinase 1 (ZmBSK1) in maize (Zea mays). Our genetic studies reveal that ZmBSK1 positively affects drought tolerance in maize plants. ZmBSK1 localizes in plasma membrane, interacts with calcium/calmodulin (Ca2+ /CaM)-dependent protein kinase (ZmCCaMK), and phosphorylates ZmCCaMK. Ser-67 is a crucial phosphorylation site of ZmCCaMK by ZmBSK1. Drought stress enhances not only the interaction between ZmBSK1 and ZmCCaMK but also the phosphorylation of Ser-67 in ZmCCaMK by ZmBSK1. Furthermore, Ser-67 phosphorylation in ZmCCaMK regulates its Ca2+ /CaM binding, autophosphorylation and transphosphorylation activity, and positively affects its function in drought tolerance in maize. Our results reveal an important role for ZmBSK1 in drought tolerance and suggest a direct regulatory mode of ZmBSK1 phosphorylating ZmCCaMK.

Ca2+/calmodulin (CaM)-dependent protein kinase (CCaMK) is an important positive regulator of abscisic acid (ABA) and abiotic stress signaling in plants and is believed to act upstream of mitogen-activated protein kinase (MAPK) in ABA signaling. However, it is unclear how CCaMK activates MAPK in ABA signaling. Here, we show that OsDMI3, a rice (Oryza sativa) CCaMK, directly interacts with and phosphorylates OsMKK1, a MAPK kinase (MKK) in rice, in vitro and in vivo. OsDMI3 was found to directly phosphorylate Thr-25 in the N-terminus of OsMKK1, and this Thr-25 phosphorylation is OsDMI3-specific in ABA signaling. The activation of OsMKK1 and its downstream kinase OsMPK1 is dependent on Thr-25 phosphorylation of OsMKK1 in ABA signaling. Moreover, ABA treatment also induces the phosphorylation in the activation loop of OsMKK1, and the two phosphorylations in the N-terminus and in the activation loop are independent. Further analyses revealed that OsDMI3-mediated phosphorylation of OsMKK1 positively regulates ABA responses in seed germination, root growth, and tolerance to both water stress and oxidative stress. Our results indicate that OsMKK1 is a direct target of OsDMI3, and OsDMI3-mediated phosphorylation of OsMKK1 plays an important role in the activation of MAPK cascade and ABA signaling.One-sentence summaryOsMKK1 is a direct target of OsDMI3, and OsDMI3-mediated phosphorylation of OsMKK1 plays an important role in the activation of MAPK cascade and ABA signaling.The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Mingyi Jiang (myjiang@njau.edu.cn)

A network control architecture and Advanced Orbiting Systems (AOS) frame switching scheme suitable for inter-satellite optical network are proposed and demonstrated. The proposed scheme will facilitate on-board data forwarding of resource and energy hungry satellite by avoiding unnecessary data packing and unpacking for bypass traffic.

Soil saline-alkalization is a major environmental stress that impairs plant growth and crop productivity. Plant roots are the primary site for the perception of soil stresses; however, the regulation mechanism engaged in the saline-alkaline stress response in plant roots is not well understood. In this study, we identified how a rice Ca(2+)/calmodulin-dependent protein kinase, OsDMI3, confers saline-alkaline tolerance in rice root growth. We measured the OsDMI3 activity by an in-gel kinase assay, Na(+) content by NaHCO(3) treatment, and Na(+) and H(+) fluxes by noninvasive micro-test technology (NMT). Furthermore, a real-time reverse-transcription polymerase chain reaction (RT-PCR) analysis was performed to identify the genes upregulated in response to NaHCO(3) treatment in rice roots. The results showed that NaHCO(3) significantly increased OsDMI3 expression and activity in rice roots. This was consistent with the results of Na(+) content and NMT that indicated OsDMI3 promoted root elongation under saline-alkaline stress by reducing root Na(+) and H(+) influx. Moreover, real-time RT-PCR analysis revealed that OsDMI3 up-regulated the transcript levels of OsSOS1 and PM-H(+)-ATPase genes OsA3 and OsA8 in saline-alkaline stressed rice plants. Collectively, our results suggest that OsDMI3 could promote saline-alkaline tolerance in rice roots by modulating the Na(+) and H(+) influx. These findings provide an important genetic target for protection of growth in rice exposed to saline-alkaline stress.

Salinity severely reduces plant growth and limits agricultural productivity. Dynamic changes and rearrangement of the plant cell wall is an important response to salt stress, but relatively little is known about the biological importance of specific cell wall components in the response. Here, we demonstrate a specific function of β-1,4-galactan in salt hypersensitivity. We found that salt stress induces the accumulation of β-1,4-galactan in root cell walls by up regulating the expression of GALACTAN SYNTHASE 1 (GALS1), which encodes a β-1,4-galactan synthase. The accumulation of β-1,4-galactan negatively affects salt tolerance. Exogenous application of D-galactose (D-Gal) causes an increase in β-1,4-galactan levels in the wild type and GALS1 mutants, especially in GALS1 overexpressors, which correlated with the aggravated salt hypersensitivity. Furthermore, we discovered that the BARLEY B RECOMBINANT/BASIC PENTACYSTEINE transcription factors BPC1/BPC2 positively regulate plant salt tolerance by repressing GALS1 expression and β-1,4-galactan accumulation. Genetic analysis suggested that GALS1 is genetically epistatic to BPC1/BPC2 with respect to the control of salt sensitivity as well as accumulation of β-1,4-galactan. Taken together, our results reveal a new regulatory mechanism by which β-1,4-galactan regulated by the BPC1/BPC2-GALS1 module aggravates salt sensitivity in Arabidopsis thaliana.

A highly enantioselective three-component hydroacyloxylation/1,4-conjugate addition of ortho-hydroxybenzyl alcohols, ynamides and carboxylic acids was developed under mild reaction conditions in the presence of a chiral N,N'-dioxide/Sc(OTf)3 complex, which went through in situ generated ortho-quinone methides with α-acyloxyenamides, delivering a range of corresponding chiral α-acyloxyenamides derivatives containing gem(1,1)-diaryl skeletons in moderate to good yields with excellent ee values. The scale-up experiment and further derivation showed the practicality of this catalytic system. In addition, a possible catalytic cycle and transition state model was proposed to elucidate the origin of the stereoselectivity based on X-ray crystal structure of the α-acyloxyenamide intermediate and product.

OsLEA5 acts as a co-regulator of a transcriptional fact ZFP36 to enhance the expression and the activity of ascorbate peroxidase OsAPX1 to regulate seed germination in rice, but it it unknown whether OsLEA5 is also crucial in plant seedlings under stress conditions. To determine this, we generated OsLEA5 overexpression and knockdown rice plants. We found that overexpression of OsLEA5 in rice plants enhanced the tolerance to drought and salt stress; in contrast, an RNA interference (RNAi) mutant of OsLEA5 rice plants was more sensitive to drought and salinity. Further investigation found that various stimuli and ABA could induce OsLEA5 expression, and OsLEA5 acted downstream of ZFP36 to be involved in ABA-induced generation of hydrogen peroxide (H2O2), and the regulation of the expression and the activities of antioxidant defense enzymes in plants leaves, and OsLEA5 contributed to stabilize ZFP36. Additionally, OsLEA5 participates in the accumulation of ABA by up-regulating ABA biosynthesis genes and down-regulating ABA metabolism genes. Moreover, we found that two homologs of OsLEA5 (5C700, short for Os05g0526700; and 5C300, short for Os05g0584300) which were induced by ABA also interacted with ZFP36 separately; interestingly, the nuclear-located 5C700 could also act as a co-activator of ZFP36 to modulate OsAPX1, while 5C300 which was down-regulated by ABA induction acted as an ABA-induced inhibitor of ZFP36 to regulate OsAPX1. Hence, our conclusion is that OsLEA5 participates in the ABA-mediated antioxidant defense to function in drought and salt stress response in rice, and the 5C subgroup of LEAs contribute by acting as co-regulators of the transcription factor ZFP36.

Seed germination is a vital developmental process. Abscisic acid (ABA) is an essential repressor of seed germination, while ROS (reactive oxygen species) also plays a vital role in regulating seed germination. ABA could inhibit the production of ROS in seed germination, but the mechanism of ABA reduced ROS production in seed germination was hitherto unknown. Here, by ChIP (chromatin immunoprecipitation)-seq, we found that ZFP36, a rice zinc finger transcription factor, could directly bind to the promoter of OsAPX1, coding an ascorbate peroxidase (APX) which has the most affinity for H2O2 (substrate; a type of ROS), and act as a transcriptional activator of OsAPX1 promoter. Moreover, ZFP36 could interact with a late embryogenesis abundant protein OsLEA5 to co-regulate the promoter activity of OsAPX1. The seed germination is highly inhibited in ZFP36 overexpression plants under ABA treatment, while an RNA interference (RNAi) mutant of OsLEA5 rice seeds were less sensitive to ABA, and exogenous ASC (ascorbate acid) could alleviate the inhibition induced by ABA. Thus, our conclusion is that OsAPX1 is a direct target of ZFP36 and OsLEA5 could interact with ZFP36 to co-regulate ABA-inhibited seed germination by controlling the expression of OsAPX1.

In plants, abscisic acid-, stress-, and ripening-induced (ASR) proteins have been shown to impart tolerance to multiple abiotic stresses such as drought and salinity. However, their roles in metal stress tolerance are poorly understood. To screen plant Cd-tolerance genes, the yeast-based gene hunting method which aimed to screen Cd-tolerance colonies from maize leaf cDNA library hosted in yeast was carried out. Here, maize ZmASR1 was identified to be putative Cd-tolerant through this survival screening strategy. In silico analysis of the functional domain organization, phylogenetic classification and tissue-specific expression patterns revealed that maize ASR1 to ASR5 are typical ASRs with considerable expression in leaves. Further, four of them were cloned for testifying Cd tolerance using yeast complementation assay. The results indicated that they all confer Cd tolerance in Cd-sensitive yeast. Then they were transiently expressed in tobacco leaves for subcellular localization analysis and for Cd-challenged lesion assay, continuously. The results demonstrated that all 4 maize ASRs tested are localized to the cell nucleus and cytoplasm in tobacco leaves. Moreover, they were confirmed to be Cd-tolerance genes in planta through lesion analysis in Cd-infiltrated leaves transiently expressing them. Taken together, our results demonstrate that maize ASRs play important roles in Cd tolerance, and they could be used as promising candidate genes for further functional studies toward improving the Cd tolerance in plants.

In plants, Ca(2+)/calmodulin-dependent protein kinase (CCaMK) is a positive regulator of abscisic acid (ABA) responses, including root growth, antioxidant defense, and tolerance of both water stress and oxidative stress. However, the underlying molecular mechanisms are poorly understood. Here, we show a direct interaction between DMI3 (Doesn't Make Infections 3), a rice (Oryza sativa) CCaMK and PP45, a type 2C protein phosphatase in rice (PP2C). This interaction involves the CaM binding domain of DMI3 and the PP2C domain of PP45. In the absence of ABA, PP45 directly inactivates DMI3 by dephosphorylating Thr-263 in DMI3. However, in the presence of ABA, ABA-induced H(2)O(2) production by the NADPH oxidases RbohB/E inhibits the activity of PP45 not only by inhibiting the expression of PP45 but also by oxidizing Cys-350 and Cys-428 residues to form PP45 intermolecular dimers. ABA-induced oxidation of Cys-350 and Cys-428 in PP45 blocked the interaction between PP45 and DMI3 and substantially prevented PP45-mediated inhibition in DMI3 activity. Genetic analysis indicated that PP45 is an important negative regulator of ABA signaling. These results reveal important pathways for the inhibition of DMI3 under the basal state and for its ABA-induced activation in rice.

Background Metal tolerance is often an integrative result of metal uptake and distribution, which are fine-tuned by a network of signaling cascades and metal transporters. Thus, with the goal of advancing the molecular understanding of such metal homeostatic mechanisms, comparative RNAseq-based transcriptome analysis was conducted to dissect differentially expressed genes (DEGs) in maize roots exposed to cadmium (Cd) stress. Results To unveil conserved Cd-responsive genes in cereal plants, the obtained 5166 maize DEGs were compared with 2567 Cd-regulated orthologs in rice roots, and this comparison generated 880 universal Cd-responsive orthologs groups composed of 1074 maize DEGs and 981 rice counterparts. More importantly, most of the orthologous DEGs showed coordinated expression pattern between Cd-treated maize and rice, and these include one large orthologs group of pleiotropic drug resistance (PDR)-type ABC transporters, two clusters of amino acid transporters, and 3 blocks of multidrug and toxic compound extrusion (MATE) efflux family transporters, and 3 clusters of heavy metal-associated domain (HMAD) isoprenylated plant proteins (HIPPs), as well as all 4 groups of zinc/iron regulated transporter protein (ZIPs). Additionally, several blocks of tandem maize paralogs, such as germin-like proteins (GLPs), phenylalanine ammonia-lyases (PALs) and several enzymes involved in JA biosynthesis, displayed consistent co-expression pattern under Cd stress. Out of the 1074 maize DEGs, approximately 30 maize Cd-responsive genes such as ZmHIPP27, stress-responsive NAC transcription factor (ZmSNAC1) and 9-cis-epoxycarotenoid dioxygenase (NCED, vp14) were also common stress-responsive genes reported to be uniformly regulated by multiple abiotic stresses. Moreover, the aforementioned three promising Cd-upregulated genes with rice counterparts were identified to be novel Cd-responsive genes in maize. Meanwhile, one maize glutamate decarboxylase (ZmGAD1) with Cd co-modulated rice ortholog was selected for further analysis of Cd tolerance via heterologous expression, and the results suggest that ZmGAD1 can confer Cd tolerance in yeast and tobacco leaves. Conclusions These novel findings revealed the conserved function of Cd-responsive orthologs and paralogs, which would be valuable for elucidating the genetic basis of the plant response to Cd stress and unraveling Cd tolerance genes. Electronic supplementary material The online version of this article (10.1186/s12864-018-5109-8) contains supplementary material, which is available to authorized users.

The plant-specific NAC transcription factors play diverse roles in various stress signaling. Alternative splicing is particularly prevalent in plants under stress. However, the investigation of cadmium (Cd) on the differential expression of the splice variants of NACs is in its infancy. Here, we identified three Cd-induced intron retention splice NAC variants which only contained the canonical NAC domain, designated as nacDomains, derived from three Cd-upregulated maize NACs. Subcellular localization analysis indicated that both nacDomain and its full-length NAC counterpart co-localized in the nucleus as manifested in the BiFC assay, thus implied that nacDomains and their corresponding NACs form heterodimers through the identical NAC domain. Further chimeric reporter/effector transient expression assay and Cd-tolerance assay in tobacco leaves collectively indicated that nacDomain-NAC heterodimers were involved in the regulation of NAC function. The results obtained here were in accordance with the model of dominant negative, which suggested that nacDomain act as the dominant negative to antagonize the regulation of NAC on its target gene expression and the Cd-tolerance function performance of NAC transcription factor. These findings proposed a novel insight into understanding the molecular mechanisms of Cd response in plants.

With the development of economic and the improvement of urbanization, the labor mobility in China is becoming more and more widespread. Also, with the accumulation of labor mobility, there has been a feature that the labor force concentrated from the underdeveloped areas to the developed areas. The characteristics of high-speed railway (HSR) such as timeliness and regional accessibility can promote the process of urbanization, induce employment. Thereby it attracts labor mobility, and creates labor agglomeration. Based on the theory of "cyclic accumulation of causality", this paper establishes the mechanism of the impact of HSR on labor agglomeration. We conduct an empirical analysis of the three cities along the HSR of the Beijing-Guangzhou line, and analyze whether the Beijing-Guangzhou line has an impact on the labor agglomeration.

Figure S1. Global view of Cd-responsive maize orthologs with rice counterparts in metabolic pathways. For the 1074 maize DEGs with rice orthologs, 471 data points were visible on the metabolic pathways (Arabidopsis seed-Molecular Networks) using MapMan software. The colored boxes indicate the Log2 ratio of Cd1h/ck1h. (PDF 1258Â kb)

Background The migration of cadmium (Cd) from contaminated soil to rice is a cause for concern. However, the molecular mechanism underlying the response of rice roots to various Cd stresses remains to be clarified from the viewpoint of the co-expression network at a system-wide scale. Results We employed a comparative RNAseq-based approach to identify early Cd-responsive differentially expressed genes (DEGs) in rice ‘Nipponbare’ seedling roots after 1 h of high-Cd treatment. A multiplicity of the identified 1772 DEGs were implicated in hormone signaling and transcriptional regulation, particularly NACs and WRKYs were all upregulated under Cd stress. All of the 6 Cd-upregulated ABC transporters were pleiotropic drug resistance proteins (PDRs), whereas all of the 6 ZRT/IRT-like proteins (ZIPs) were consistently downregulated by Cd treatment. To further confirm our results of this early transcriptomic response to Cd exposure, we then conducted weighted gene co-expression network analysis (WGCNA) to re-analyze our RNAseq data in combination with other 11 previously published RNAseq datasets for rice roots exposed to diverse concentrations of Cd for extended treatment periods. This integrative approach identified 271 transcripts as universal Cd-regulated DEGs that are key components of the Cd treatment coupled co-expression module. A global view of the 164 transcripts with annotated functions in pathway networks revealed several Cd-upregulated key functional genes, including transporter ABCG36/OsPDR9, 12-oxo-phytodienoic acid reductases (OPRs) for JA synthesis, and ZIM domain proteins JAZs in JA signaling, as well as OsWRKY10, NAC, and ZFP transcription factors. More importantly, 104 of these, including ABCG36/OsPDR9, OsNAC3, as well as several orthologs in group metalloendoproteinase, plastocyanin-like domain containing proteins and pectin methylesterase inhibitor, may respond specifically to various Cd pressures, after subtracting the 60 general stress-responsive genes reported to be commonly upregulated following multiple stresses. Conclusion An integrative approach was implemented to identify DEGs and co-expression network modules in response to various Cd pressures, and 104 of the 164 annotatable universal Cd-responsive DEGs may specifically respond to various Cd pressures. These results provide insight into the universal molecular mechanisms beneath the Cd response in rice roots, and suggest many promising targets for improving the rice acclimation process against Cd toxicity. Electronic supplementary material The online version of this article (10.1186/s12870-017-1143-y) contains supplementary material, which is available to authorized users.

Summary In maize (Zea mays), the mitogen-activated protein kinase ZmMPK5 has been shown to be involved in abscisic acid (ABA)-induced antioxidant defence and to enhance the tolerance of plants to drought, salt stress and oxidative stress. However, the underlying molecular mechanisms are poorly understood. Here, using ZmMPK5 as bait in yeast two-hybrid screening, a protein interacting with ZmMPK5 named ZmABA2, which belongs to a member of the short-chain dehydrogenase/reductase family, was identified. Pull-down assay and bimolecular fluorescence complementation analysis and co-immunoprecipitation test confirmed that ZmMPK5 interacts with ZmABA2 in vitro and in vivo. Phosphorylation of Ser173 in ZmABA2 by ZmMPK5 was shown to increase the activity of ZmABA2 and the protein stability. Various abiotic stimuli induced the expression of ZmABA2 in leaves of maize plants. Pharmacological, biochemical and molecular biology and genetic analyses showed that both ZmMPK5 and ZmABA2 coordinately regulate the content of ABA. Overexpression of ZmABA2 in tobacco plants was found to elevate the content of ABA, regulate seed germination and root growth under drought and salt stress and enhance the tolerance of tobacco plants to drought and salt stress. These results suggest that ZmABA2 is a direct target of ZmMPK5 and is involved in ABA biosynthesis and functions.

Brassinosteroids (BRs) have been shown to enhance stress tolerance by inducing antioxidant defense systems. However, the mechanisms of BR-induced antioxidant defense in plants remain to be determined. In this study, the role of calcium (Ca(2+)) and maize calcium/calmodulin-dependent protein kinase (CCaMK), ZmCCaMK, in BR-induced antioxidant defense, and the relationship between ZmCCaMK and Ca(2+) in BR signaling were investigated. BR treatment led to a significant increase in cytosolic Ca(2+) concentration in protoplasts from maize mesophyll, and Ca(2+) was shown to be required for BR-induced antioxidant defense. Treatment with BR induced increases in gene expression and enzyme activity of ZmCCaMK in maize leaves. Transient overexpression and silencing of ZmCCaMK in maize protoplasts demonstrated that ZmCCaMK was required for BR-induced antioxidant defense. The requirement for CCaMK was further investigated using a loss-of-function mutant of OsCCaMK, the orthologous gene of ZmCCaMK in rice. Consistent with the findings in maize, BR treatment could not induce antioxidant defense in the rice OsCCAMK mutant. Furthermore, Ca(2+) was required for BR-induced gene expression and activation of ZmCCaMK, while ZmCCaMK was shown to enhance the BR-induced increase in cytosolic Ca(2+) concentration. Moreover, our results also showed that ZmCCaMK and H2O2 influenced each other. These results indicate that Ca(2+) works together with ZmCCaMK in BR-induced antioxidant defense, and there are two positive feedback loops between Ca(2+) or H2O2 and ZmCCaMK in BR signaling in maize.

A Venn diagram showing the intersections of Cd-responsive 1772 DEGs and those identified in previous two reports. Rice roots exposed to 1 h of Cd treatment (Cd1h) and its control (ck1h) are sampled in our lab. The published rice roots RNAseq data of medium Cd stress for 1 h (MCd1) [27], and the microarray analysis of low Cd stress for 3 h (lowCd) [21] are listed in Additional file 6: Dataset 1. (PPT 373 kb)