Comprehensive evaluation of salt-alkali tolerance of rice germplasms at germination and seedling stages and analysis of salt-tolerant genes / 生物工程学报

Cultivating salt-alkali tolerant rice varieties is one of the important ways to meet the increasing food demand of growing global population. In this study, twenty-one rice germplasms with different salt-alkali tolerance were treated with six salt-alkali concentrations at germination and seedling stages. The germination potential, germination rate, shoot length, root length, root number, fresh weight of shoot and seedlings were measured. The average value of salt damage rate was used to evaluate the salt-alkali tolerance. As the salt-alkali concentration increases, the inhibition on seed germination and growth became more obvious. Upon treatment with 1% NaCl plus 0.25% NaHCO3, the salt damage rate of germination rate has the largest variation, ranging from 0% to 89.80%. The salt damage rate of each trait shows a similar trend at all concentrations. Four germplasm resources with strong salt-alkali tolerance (Dajiugu, Nippobare, Mowanggu and 02428) and 7 sensitive germplasms were screened. The salt-tolerant gene sequence of 4 salt-alkali tolerant varieties and 3 sensitive germplasms were analyzed. OSHAL3 and OsRR22 were identical among the 7 germplasms, but SKC1 and DST showed clear variations between the salt-alkali tolerant and sensitive germplasms. Besides the salt-alkali tolerant germplasm resources, this study can also serve as a reference for mining of genes involved in salt-alkali tolerance and breeding of salt-alkali tolerant rice varieties.

Mechanism of salicylic acid ameliorates salt-induced changes in Andrographis paniculata / 中国中药杂志

In this study, Andrographis paniculata seedlings were used as experimental materials to study the effects of salicylic acid(SA) on the growth and effective component accumulation of A. paniculata under NaCl stress. The results showed that with the increase of NaCl concentration, the growth of A. paniculata seedlings was significantly inhibited, and the content of carotene and carotenoid decreased. The activity of antioxidant enzyme was enhanced. At the same time, the contents of proline, proline and soluble protein were on the rise. The contents of andrographolide, new andrographolide and deoxyandrographolide showed an upward trend, while deoxyandrographolide showed a downward trend. Treatment with 100 mmol·L~(-1) NaCl+5 mg·L~(-1) SA showed a significant increase in antioxidant enzyme activity in A. paniculata leaves. Treatment with 100 mmol·L~(-1) NaCl+10 mg·L~(-1) SA showed significant changes in soluble protein and proline content in A. paniculata leaves, while MDA content in A. paniculata leaves significantly decreased. 10 mg·L~(-1) SA had the best effect on the growth of A. paniculata seedlings under salt stress. Under the treatment of 50 mmol·L~(-1) NaCl+10 mg·L~(-1) SA, fresh weight, dry weight and leaf dry weight of A. paniculata seedlings reached the highest level, which were 1.02, 1.09 and 1.11 times of those in the control group, respectively. The concentrations of NaCl and 10 mg·L~(-1) SA were significantly higher than those of the control group. Four key enzyme genes of A. paniculata diterpene lactone synthesis pathway were selected to explore the molecular mechanism of salicylic acid to alleviate salt stress. With the increase of salt stress, the relative expressions of HMGR, GGPS and ApCPS were up-regulated, indicating that salt stress may enhance the synthesis of A. paniculata diterpene lactone through MVA pathway. SA can effectively promote the growth and development of A. paniculata under salt stress, improve its osmotic regulation and antioxidant capacity, improve its salt tolerance, and alleviate the effects of salt stress on A. paniculata.

Transcriptome analysis of phosphorus stress responsiveness in the seedlings of Dongxiang wild rice (Oryza rufipogon Griff.)

Abstract Background: Low phosphorus availability is a major factor restricting rice growth. Dongxiang wild rice (Oryza rufipogon Griff.) has many useful genes lacking in cultivated rice, including stress resistance to phosphorus deficiency, cold, salt and drought, which is considered to be a precious germplasm resource for rice breeding. However, the molecular mechanism of regulation of phosphorus deficiency tolerance is not clear. Results: In this study, cDNA libraries were constructed from the leaf and root tissues of phosphorus stressed and untreated Dongxiang wild rice seedlings, and transcriptome sequencing was performed with the goal of elucidating the molecular mechanisms involved in phosphorus stress response. The results indicated that 1184 transcripts were differentially expressed in the leaves (323 up-regulated and 861 down-regulated) and 986 transcripts were differentially expressed in the roots (756 up-regulated and 230 down-regulated). 43 genes were up-regulated both in leaves and roots, 38 genes were up-regulated in roots but down-regulated in leaves, and only 2 genes were down-regulated in roots but up-regulated in leaves. Among these differentially expressed genes, the detection of many transcription factors and functional genes demonstrated that multiple regulatory pathways were involved in phosphorus deficiency tolerance. Meanwhile, the differentially expressed genes were also annotated with gene ontology terms and key pathways via functional classification and Kyoto Encyclopedia of Gene and Genomes pathway mapping, respectively. A set of the most important candidate genes was then identified by combining the differentially expressed genes found in the present study with previously identified phosphorus deficiency tolerance quantitative trait loci. Conclusion: The present work provides abundant genomic information for functional dissection of the phosphorus deficiency resistance of Dongxiang wild rice, which will be help to understand the biological regulatory mechanisms of phosphorus deficiency tolerance in Dongxiang wild rice.

Characterization and expression of codon optimized soybean phytase gene in E. coli.

Phytic acid, the major storage form of phosphorus in plant seeds is degraded by the phytases to yield inositol and free phosphate, contributing thereby to the improved bioavailability of phytate phosphorus and essential minerals in plant foods and simultaneous reduction in phosphorus pollution of the terrestrial and aquatic ecosystems. As a possible strategy for altering seed phytate levels, the approach involving reduction of phytate content by ectopically expressing endogenous phytase gene during seed development of soybean (Glycine max L. cv. Pusa-20) was attempted in the present study. Semi-quantitative RT-PCR revealed the maximum expression of phytase gene transcripts in germinating cotyledons (~10 days after germinations), compared to other vegetative tissues. A full-length phytase cDNA was amplified from the germinating seedlings by splicing by overlap extension (SOE)-PCR and its sequence analysis revealed an open-reading-frame of 1644 bp, including an N terminal signal peptide of 28 amino acids. Predicted amino acid sequence (547-aa) of molecular mass 62 kDa on alignment with related purple acid phosphatases in other plants shared five conserved domains and seven invariant amino acids involved in coordination of the metals in the binuclear center of purple acid phosphatases. Owing to a large number of E. coli low-usage codons in soybean phytase gene, the modified gene was cloned into a prokaryotic expression vector pET-28a (+) and its expression in E. coli was confirmed by SDS-PAGE and Western blot analysis. Bioassay of the crude expression product in E. coli revealed a functional phytase gene, showing a great potential for developing low phytate transgenic soybean through its seed-specific overexpression in the early stages of seed development.

Parâmetros genéticos de frutos, sementes e plântulas de Jatropha ribifolia (Pohl) Baill. (Euphorbiaceae) / Genetic parameters of fruits, seeds and seedlings of Jatropha ribifolia (Pohl) Baill. (Euphorbiaceae)

O objetivo deste trabalho foi estimar parâmetros genéticos de frutos, sementes e plântulas de Jatropha ribifolia (Pohl) Baill., subsidiando futuros programas de melhoramento e conservação genética. Foram selecionadas 20 matrizes da espécie e os frutos coletados em área de Caatinga, no Município de Jequié - BA / Brasil. Para descrição morfológica foram observadas características de 50 frutos e 50 sementes. Para germinação foi utilizado o delineamento experimental inteiramente casualizado com 20 tratamentos (progênie) e três repetições de 20 sementes. O fruto de J. ribifolia é seco, cápsula loculicida e septicida, endocarpo lenhoso e deiscência explosiva (autocórica). A semente é oval, endospérmica, de testa lisa, com diferentes colorações e carúncula presa na parte ventral. O hilo é visível e a rafe bem marcada longitudinalmente. A germinação é hipógea-criptocotiledonar. O tempo médio para germinação foi de 10 a 40 dias. As matrizes de J. ribifolia estudadas apresentaram variabilidade genética significativa para a maioria dos caracteres estudados.

The aim of this study was to estimate genetic parameters of fruits, seeds and seedlings of Jatropha ribifolia (Pohl) Baill, subsidizing future breeding and genetic conservation programs. Twenty matrices of the species and the fruits collected in the Caatinga area in the city of Jequié - BA / Brazil were selected. For morphological description, the features of 50 fruits and 50 seeds were observed. For germination, completely randomized design was used with 20 treatments (progeny) and three replicates of 20 seeds. J. ribifolia fruit is dry and has loculicidal and septicidal capsule, woody endocarp and explosive dehiscence (autochory). The seed is oval, endospermic and has smooth testa and different colors, with caruncle attached to the ventral part. The hilum is visible and the raphe is longitudinally marked. Germination is hypogeal-cryptocotylar. The average time for germination was from 10 to 40 days. The matrices of J. ribifolia showed significant genetic variability for most of the studied traits.

Transgenic lettuce seedlings carrying hepatitis B virus antigen HBsAg

The obtainment of transgenic edible plants carrying recombinant antigens is a desired issue in search for economic alternatives viewing vaccine production. Here we report a strategy for genetic transformation of lettuce plants (Lactuca sativa L.) using the surface antigen HBsAg of hepatitis B virus. Transgenic lettuce seedlings were obtained through the application of a regulated balance of plant growth regulators. Genetic transformation process was acquired by cocultivation of cotyledons with Agrobacterium tumefaciens harboring the recombinant plasmid. It is the first description of a lettuce Brazilian variety "Vitória de Verão" genetically modified.

Regulation of the expression of GA-insensitive gene homolog by light in Oryza sativa c.v. DongJin.

To understand the mechanism by which light regulates a gibberellin (GA)-insensitive gene in DongJinByeo (Oryza sativa cv DongJin), both green and etiolated DongJinByeo seedlings were submerged in water and treated with GA. Total RNA from the seedlings was isolated and hybridized with cDNA of a GA-insensitive gene homolog. The amount of transcript for the GA-insensitive gene homolog was higher in green seedlings than in etiolated seedlings in the absence of GA. However upon the addition of GA, greater accumulations of the gene transcript occurred in etiolated seedlings than in green seedlings. This result indicates the possibility that the expression of the GA-insensitive gene homolog transcript may be inhibited by light in the presence of GA. Light seems to regulate multilaterally the accumulation of the transcript of the GA-insensitive gene homolog in DongJinByeo (Oryza sativa cv DongJin).

Annotation and BAC/PAC localization of nonredundant ESTs from drought-stressed seedlings of an indica rice.

To decipher the genes associated with drought stress response and to identify novel genes in rice, we utilized 1540 high-quality expressed sequence tags (ESTs) for functional annotation and mapping to rice genomic sequences. These ESTs were generated earlier by 3'-end single-pass sequencing of 2000 cDNA clones from normalized cDNA libraries constructed form drought-stressed seedlings of an indica rice. A rice UniGene set of 1025 transcripts was constructed from this collection through the BLASTN algorithm. Putative functions of 559 nonredundant ESTs were identified by BLAST similarity search against public databases. Putative functions were assigned at a stringency E value of 10(-6) in BLASTN and BLASTX algorithms. To understand the gene structure and function further, we have utilized the publicly available finished and unfinished rice BAC/PAC (BAC, bacterial artificial chromosome; PAC, P1 artificial chromosome) sequences for similarity search using the BLASTN algorithm. Further, 603 nonredundant ESTs have been mapped to BAC/PAC clones. BAC clones were assigned by a homology of above 95% identity along 90% of EST sequence length in the aligned region. In all, 700 ESTs showed rice EST hits in GenBank. Of the 325 novel ESTs, 128 were localized to BAC clones. In addition, 127 ESTs with identified putative functions but with no homology in IRGSP (International Rice Genome Sequencing Program) BAC/PAC sequences were mapped to the Chinese WGS (whole genome shotgun contigs) draft sequence of the rice genome. Functional annotation uncovered about a hundred candidate ESTs associated with abiotic stress in rice and Arabidopsis that were previously reported based on microarray analysis and other studies. This study is a major effort in identifying genes associated with drought stress response and will serve as a resource to rice geneticists and molecular biologists.