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Pareuchiloglanis longicauda, a Sisorid fish that is distributed in the upper Pearl River. In this study, the complete mitogenome of P. longicauda was sequenced using traditional Sanger sequencing a...

MADS-box proteins are important transcription factors that play essential roles in various aspects of plant development, particularly in flower development. In this study, we performed the identification and functional characterization of CsMADS09 isolated from cucumber (Cucumis sativus L.). CsMADS09 contains a 648-bp open reading frame encoding 215 amino acid residues, and shares high sequence identities with the members of the AP1/FUL family of MADS-box proteins, especially the euAPETALA1 (euAP1) subclade. Many cis-elements related to plant development, stress response, and hormones were identified in the promoter region of CsMADS09. Quantitative real-time polymerase chain reaction results showed that CsMADS09 was mainly expressed in reproductive tissues such as male flowers and unexpanded ovaries, while its expression was low in roots and only traceable in fertilized ovaries. Moreover, the results revealed that CsMADS09 expression tended to decline during male flower development and stayed nearly constant during female flower development. Ectopic expression of CsMADS09 resulted in earlier flowering and abnormal leaf development in transgenic Arabidopsis. This study is the first functional analysis of an AP1-like gene from cucumber and provides some clues for revealing the molecular mechanisms of flower development in cucumber.

Superoxide dismutase (SOD) proteins, which are widely present in the plant kingdom, play vital roles in response to abiotic stress. However, the functions of cucumber SOD genes in response to environmental stresses remain poorly understood. In this study, a SOD gene CsCSD1 was identified and functionally characterized from cucumber (Cucumis sativus). The CsCSD1 protein was successfully expressed in E. coli, and its overexpression significantly improved the tolerance of host E. coli cells to salinity stress. Besides, overexpression of CsCSD1 enhanced salinity tolerance during germination and seedling development in transgenic Arabidopsis plants. Further analyses showed that the SOD and CAT (catalase) activities of transgenic plants were significantly higher than those of wild-type (WT) plants under normal growth conditions as well as under NaCl treatment. In addition, the expression of stress-response genes RD22, RD29B and LEA4-5 was significantly elevated in transgenic plants. Our results demonstrate that the CsCSD1 gene functions in defense against salinity stress and may be important for molecular breeding of salt-tolerant plants.

Environmental stressors, especially low temperature, are very common on the earth's dryland systems. Terrestrial cyanobacteria have evolved with cold adaptability in addition to extreme dryness and high irradiation resistance. The dryland soil surface-dwelling species, Nostoc flagelliforme, serves as a potential model organism to gain insights into cyanobacterial cold adaptation. In this study, we performed transcriptomic analysis of N. flagelliforme samples in response to low temperature. The results revealed that the biological processes, such as terpenoid biosynthetic process, oxidoreductase activity, carbohydrate metabolism, biosynthesis of secondary metabolites, lipid and nitrogen metabolism, were significantly and dynamically changed during the cold stress. It was noteworthy that the transcription of the denitrification pathway for ammonia accumulation was enhanced, implying an importance for nitrogen utilization in stress resistance. In addition, characterization of a cold-responsive hypothetical gene csrnf1 found that it could greatly improve the cold-resistant performance of cells when it was heterologously expressed in transgenic Nostoc sp. PCC 7120. It was also found that csrnf1 transgenic strain exhibited resistance to nitrogen-deficient environmental stress. Considering that dryland cyanobacteria have to cope with low temperature on infertile soils, this study would enrich our understanding on the importance of multifunction of the genes for environmental cold adaptation in drylands.

Cysteine-rich polycomb-like protein (CPP) transcription factors are a small gene family involved in the regulation of plant growth, development and stress response. Genome-wide identification and characterization of CPP gene family have been carried out in several plant species. However, no comprehensive phylogenetic analysis or expression profiling of CPP genes in Cucumis sativus has been reported. In this study, we characterized the CPP family genes in C. sativus, and 5 CPP candidate genes were found in cucumber genome. CPP proteins from cucumber and other plant species were classified into two groups, which were further divided into five subgroups based on the phylogenetic distribution. Most CPP genes in the same subgroup shared similar gene structures and conserved motifs. Transcriptome data revealed that CsCPP genes were expressed in leaves, ovaries, flowers, stems, roots, and tendril tissues. qRT-PCR expression analysis showed that many CsCPP genes exhibited different expression patterns in cucumber leaves under abiotic stresses including salt, cold, drought, and ABA. These results demonstrate that cucumber CPP gene family may play critical roles in plant development as well as in the responses to environmental stresses.

Echinenone and canthaxanthin are important carotenoid pigments with food and industrial applications. Biosynthesis of echinenone and/or canthaxanthin is catalyzed by β-carotene ketolase (CrtO), with β-carotene as the substrate. In this study, we generated transgenic Nostoc sp. PCC 7120 overexpressing a heterologous crtO gene from Nostoc flagelliforme and evaluated the productivity of both pigments. Normal (BG11 medium, 30 °C) and osmotic stress (BG11 medium supplemented with 0.4 M mannitol, 30 °C) conditions were used for cultivation. As compared to control strain, production of echinenone and canthaxanthin in transgenic strain were respectively increased by more than 16 % and 80 %, under either normal or osmotic stress conditions. Especially upon the stress condition, higher proportion of echinenone and canthaxanthin in total pigments was achieved, which should be beneficial for downstream separation and purification. In addition, transgenic strain showed drought tolerance and could revive from desiccation treatment after rewetting. Thus, this study provided technical clues for production of both pigments in engineered cyanobacteria as well as for cyanobacterial anhydrobiotic engineering.

Plant glutathione peroxidases (GPXs) are non-heme thiol peroxidases that play vital roles in maintaining H(2)O(2) homeostasis and regulating plant response to abiotic stress. Here, we performed a comparative genomic analysis of the GPX gene family in cucumber (Cucumis sativus). As a result, a total of 6 CsGPX genes were identified, which were unevenly located in four out of the seven chromosomes in cucumber genome. Based on the phylogenetic analysis, the GPX genes of cucumber, Arabidopsis and rice could be classified into five groups. Analysis of the distribution of conserved domains of GPX proteins showed that all these proteins contain three highly conserved motifs, as well as other conserved sequences and residues. Gene structure analysis revealed a conserved exon–intron organization pattern of these genes. Through analyzing the promoter regions of CsGPX genes, many hormone-, stress-, and development-responsive cis-elements were identified. Moreover, we also investigated their expression patterns in different tissues and developmental stages as well as in response to abiotic stress and x acid (ABA) treatments. The qRT-PCR results showed that the transcripts of CsGPX genes varied largely under abiotic stress and ABA treatments at different time points. These results demonstrate that cucumber GPX gene family may function in tissue development and plant stress responses. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13205-018-1185-3) contains supplementary material, which is available to authorized users.

Genetically engineered (GE) crops with resistance to environmental stresses are one of the most important solutions for future food security. Numerous genes associated to plant stress resistance have been identified and characterized. However, the current reality is that only a few transgenic crops expressing prokaryotic genes are successfully applied in field conditions. These few prokaryotic genes include Agrobacterium strain CP4 EPSPS gene, Bacillus thuringiensis Cry1Ab gene and a bacterial chaperonin gene. Thus, the excavation of potentially critical genes still remains an arduous task for crop engineering. Terrestrial macroscopic cyanobacteria, Nostoc commune and Nostoc flagelliforme, which exhibit extreme resistance to desiccation stress, may serve as new prokaryotic bioresources for excavating critical genes. Recently, their marker gene wspA was heterologously expressed in Arabidopsis plant and the transgenics exhibited more flourishing root systems than wild-type plants under osmotic stress condition. In addition, some new genes associated with drought response and adaptation in N. flagelliforme are being uncovered by our ongoing RNA-seq analysis. Although the relevant work about the terrestrial macroscopic cyanobacteria is still underway, we believe that the prospect of excavating their critical genes for application in GE crops is quite optimistic.

The mitogen-activated protein kinase kinases (MKK) represent a small gene family that is located at the center of the MAPK cascade and play an important role in responses to biotic and abiotic stresses and in plant growth and development. Here, we report the cloning of an MKK gene from Brassica napus, BnMKK1 (GenBank Accession No. HQ916282), by RT-PCR. The BnMKK1 cDNA is 1,447 bp in length with an open reading frame of 1,092 bp. The gene encodes a putative MKK protein that contains a conserved motif S/TxxxxxS/T (where x represents any amino acid) and a MPK docking domain in its N-terminal extension. The orthologues of the BnMKK1 protein are highly conserved among mosses, ferns, dicotyledons and monocotyledons. Southern hybridization revealed the presence of more than two copies of the BnMKK1 homologues in the genome of B. napus. Quantitative reverse transcription–polymerase chain reaction analyses showed that the BnMKK1 transcripts accumulated in response to cold, ABA (abscisic acid) and MeJA (methyl jasmonate) but declined in response to mannitol, NaCl, H2O2, and SA (salicylic acid). The inhibitors of MAPK activation, PD98059 and U0126, did not inhibit BnMKK1 transcription. BnMKK1 transgenic tobacco plants grew slower and showed significantly delayed flower times compared to the wild type. Their root development was insensitive to treatment with 100 mM IAA (indole-3-acetic acid). The detached leaves from the transgenic BnMKK1 tobacco plants strengthened the inhibition to bacterial development at later growth stages. The overexpression of BnMKK1 leads to rapid water loss and enhanced sensitivities to drought stress in transgenic tobacco plants. These results show that BnMKK1 plays an important role in the response of plants to pathogenic bacteria and drought stress.

Nostoc flagelliforme, a filamentous nitrogen-fixing cyanobacterium, is widely distributed in arid steppes of the west and northwestern parts of China. However, as a food delicacy this species has been overexploited from 1970 to 2000. Moreover, overgrazing, land reclamation and the removal of medicinal herbs have caused severely reduced vegetation coverage there. In this communication, a badly damaged but slowly rehabilitating N. flagelliforme-inhibiting steppe is described, and the rehabilitation of desertified steppes by the renewed growth of N. flagelliforme is proposed. The restoration of this dominant nitrogen supplier would be an ecologically sustainable solution for supplementing current measures already taken in the desertified regions. In addition, a goal of 50%–60% vegetation coverage is proposed by the N. flagelliforme restoration.

Environmental abiotic stresses are limiting factors for less tolerant organisms, including soil plants. Abiotic stress tolerance-associated genes from prokaryotic organisms are supposed to have a bright prospect for transgenic application. The drought-adapted cyanobacterium Nostoc flagelliforme is arising as a valuable prokaryotic biotic resource for gene excavation. In this study, we evaluated the salt-tolerant function and application potential of a candidate gene drnf1 from N. flagelliforme, which contains a P-loop NTPase (nucleoside-triphosphatase) domain, through heterologous expression in two model organisms Synechocystis sp. PCC 6803 and Arabidopsis thaliana. It was found that DRNF1 could confer significant salt tolerance in both transgenic organisms. In salt-stressed transgenic Synechocystis, DRNF1 could enhance the respiration rate, slow-down the accumulation of exopolysaccharides, up-regulate the expression of salt tolerance-related genes at a higher level, such as those related to glucosylglycerol synthesis, Na+/H+ antiport, and sugar metabolism, and maintain a better K+/Na+ homeostasis, as compared to the wild-type strain. These results imply that DRNF1 could facilitate salt tolerance by affecting the respiration metabolism and indirectly regulating the expression of important salt-tolerant genes. Arabidopsis was employed to evaluate the salt tolerance-conferring potential of DRNF1 in plants. The results show that it could enhance the seed germination and shoot growth of transgenic plants under saline conditions. In general, a novel prokaryotic salt-tolerant gene from N. flagelliforme was identified and characterized in this study, enriching the candidate gene pool for genetic engineering in plants.

Calcium-dependent protein kinases (CDPKs) control plant development and response to various stress environments through the important roles in the regulation of Ca(2+) signaling. Thirty-one CDPK genes have been identified in the rice genome by a complete search of the genome based upon HMM profiles. In this study, the expression of this gene family was analyzed using the Affymetrix rice genome array in three rice cultivars: Minghui 63, Zhenshan 97, and their hybrid Shanyou 63 independently. Twenty-seven tissues sampled throughout the entire rice life-span were studied, along with three hormone treatments (GA3, NAA and KT), applied to the seedling at the trefoil stage. All 31 genes were found to be expressed in at least one of the experimental stages studied and revealed diverse expression patterns. We identified differential expression of the OsCPK genes in the stamen (1 day before flowering), the panicle (at the heading stage), the endosperm (days after pollination) and also in callus, in all three cultivars. Eight genes, OsCPK2, OsCPK11, OsCPK14, OsCPK22, OsCPK25, OsCPK26, OsCPK27 and OsCPK29 were found dominantly expressed in the panicle and the stamen, and five genes, OsCPK6, OsCPK7, OsCPK12, OsCPK23 and OsCPK31 were up-regulated in the endosperm stage. The OsCPK genes were also found to be regulated in rice seedlings subjected to different hormone treatment conditions, however their expression were not the same for all varieties. These diverse expression profiles trigger the functional analysis of the CDPK family in rice.

Plant heat shock proteins (Hsps) facilitate protein folding or assembly under diverse developmental and adverse environmental conditions. Nine OsHsps were identified in our previous study from a proteomic analysis of rice cv. IRAT 109 leaf samples at the seedling stage under drought stress. To obtain additional information on the 9 OsHsp genes, this study focused on an expression profile analysis at different development stages throughout the life cycle of rice, and under different abiotic stresses and phytohormone treatments. The 9 genes exhibited distinctive expression patterns in different organs or development stages. Five of the genes (OsHsp72.90, OsHsp72.57, OsHsp71.18, OsHsp24.15 and OsHsp18.03) showed high expression in the endosperm, indicating that OsHsp genes may play important roles in rice seed development. All 9 OsHsps were up-regulated under heat, polyethylene glycol, and abscisic acid treatment, whereas salt stress caused up-regulation of 6 genes (OsHsp93.04, OsHsp71.10, OsHsp71.18, OsHsp72.57, OsHsp24.15 and OsHsp18.03) and cold stress resulted in down-regulation of OsHsp93.04 and OsHsp72.57. These diverse expression profiles imply potential functional diversity of the Hsp gene family in rice.