SRAP analysis of the genetic diversity of wild castor (Ricinus communis L.) in South China.

Castor bean is an important seed oil crop. Castor oil is a highly demanded oil for several industrial uses. Currently, castor bean varieties suffer from low productivity and high risk of insect pests and diseases. It is in urgent need to mine elite genes from wild materials for castor breeding. 29 pairs of polymorphic SRAP primers out of 361 pairs were used to analyse the genetic diversity of 473 wild castor materials from South China. 203 bands were amplified by the 29 pairs of primers, of which 169 bands were polymorphic, with a polymorphic percentage of 83.25%. With an average number of alleles per locus (Ap) of 1.801, average number of effective alleles per locus (Ae) of 1.713 and average percentage of polymorphic loci (P) of 90.04%, these primers were proven to be useful and effective. Nei' genetic distance between the materials ranged from 1.04 to 25.02, with an average of 13.03. At the genetic distance of 25.02, the materials clustered into two major groups, consistent with the result of population structure analysis. However, more subgroups existed between 5.21 and 13.32. Although not all the materials from the same region were clustered in the same group, an obvious trend existed where the groups were related to regions to a great extent. Based on multiple indices, the genetic diversity of materials from Hainan was the lowest. However, there was not much difference between West Guangdong and Guangxi, although the former was slightly higher. Moderate genetic differentiation was observed in wild materials in South China. The genetic differentiation mainly occurred within population, with maximum differentiation in Guangxi, followed by West Guangdong and the minimum in Hainan. Nonetheless, there was an extensive geneflow between populations. The above results provided a direction for the conservation and breeding application of these materials

Efficient culture protocol for plant regeneration from cotyledonary petiole explants of Jatropha curcas L.

A high-frequency and reproducible protocol for induction of adventitious shoot buds and plant regeneration from cotyledonary petiole explants of Jatropha curcas L. has been developed. The cotyledonary petiole explants of J. curcas cultured directly on medium supplemented with thidiazuron (TDZ) induce regeneration of poor quality shoot buds that have a low regeneration frequency. However, treating the explants with high concentrations (10–60 mg/L) of TDZ solution for certain time periods (5–80 min) significantly increased the regeneration frequency and improved the quality of the regenerated shoot buds. The best shoot buds induction (88.42%) and number of shoot buds (12.67) per explant were observed when in vitro explants were treated with 20 mg/L TDZ solution for 20 min before being transferred on hormone-free medium after 30 days. Regeneration was also influenced by the orientation (horizontal or vertical) of the explants on the medium, and by the origin of the cotyledonary petioles (in vitro or in vivo) used for the preparation of explants. We performed subsequent experiments for elongation and rooting of the regenerated shoot buds. Addition of L-arginine to the medium was conducive to the elongation of the shoot buds. A concentration of 7.5 mg/L L-arginine yielded the best results. The elongated shoots could initiate roots to become intact plantlets in half-strength Murashige and Skoog medium containing 0.1 mg/L indole-3-butyric acid. After acclimatization, these plantlets could be transplanted to the soil and the growth was normal. Therefore, application of the methods described here helped to increase plant regeneration efficiency

RcPAL, a key gene in lignin biosynthesis in Ricinus communis L.

Abstract Background Castor (Ricinus communis L.) is an important seed oil crop. Castor oil is a highly demanded oil for several industrial uses. Current castor bean varieties suffer from low productivity and high risk of insect pests and diseases. High productive and pest/disease resistance varieties are needed. Lignin has been associated to the resistance for pest, disease and lodging. Lignin is produced from several metabolites of the phenylpropanoid pathway. PAL is the key enzyme of the phenylpropanoid pathway. The gene PAL may assist in the improvement of resistance of castor bean. Results The RcPAL CDs was amplified and its function was examined by transgenic overexpression and antisense expression, lignin histochemical staining, real-time PCR, lignin content measurement and morphological investigation. Its full length was 2145 bp, encoding 714 amino acids. The overexpression of RcPAL (7.2 times) increased significantly the PAL activity, dyeing depth of xylem cells and lignin content (14.44%), resulting in a significantly lower plant height, deeper and thicker blade, more green leaves, shorter internode, thicker stem diameter, and opposite in antisense expression plants (lignin content lowered by 27.1%), demonstrated that the gene RcPAL was a key gene in castor lignin biosynthesis. Conclusions The gene RcPAL is a key gene in castor lignin biosynthesis and can be induced to express under mechanical damage stress. When up-regulated, it increased the lignin content significantly and dwarfed the plant height, and opposite when down-regulated. The gene RcPAL may assist in the improvement of resistance and plant type of castor bean

Divergent Evolutionary Patterns of NAC Transcription Factors Are Associated with Diversification and Gene Duplications in Angiosperm

NAC (NAM/ATAF/CUC) proteins constitute one of the biggest plant-specific transcription factor (TF) families and have crucial roles in diverse developmental programs during plant growth. Phylogenetic analyses have revealed both conserved and lineage-specific NAC subfamilies, among which various origins and distinct features were observed. It is reasonable to hypothesize that there should be divergent evolutionary patterns of NAC TFs both between dicots and monocots, and among NAC subfamilies. In this study, we compared the gene duplication and loss, evolutionary rate, and selective pattern among non-lineage specific NAC subfamilies, as well as those between dicots and monocots, through genome-wide analyses of sequence and functional data in six dicot and five grass lineages. The number of genes gained in the dicot lineages was much larger than that in the grass lineages, while fewer gene losses were observed in the grass than that in the dicots. We revealed (1) uneven constitution of Clusters of Orthologous Groups (COGs) and contrasting birth/death rates among subfamilies, and (2) two distinct evolutionary scenarios of NAC TFs between dicots and grasses. Our results demonstrated that relaxed selection, resulting from concerted gene duplications, may have permitted substitutions responsible for functional divergence of NAC genes into new lineages. The underlying mechanism of distinct evolutionary fates of NAC TFs shed lights on how evolutionary divergence contributes to differences in establishing NAC gene subfamilies and thus impacts the distinct features between dicots and grasses

The utilization of Ricinus communis in the phytomanagement of heavy metal contaminated soils

Soil contamination with toxic metals is a major global concern due to their effects on plants and the ecosystem. In contaminated soils, some plant species have the ability to remediate heavy metals. Ricinus communis L., is an industrial crop plant gaining popularity in the remediation of heavy metal contaminated soils owing to its strong and deep penetrating roots aiding high metal accumulation and large biomass level. Ricinus communis can tolerate high amounts of metals by adopting different strategies, which include the production of antioxidant enzymes, subcellular localization, and exudation of organic acid. At the molecular level, R. communis can tolerate metal stress by activating stress-responsive genes. Proper selection of metal-tolerant R. communis cultivars is effective in the remediation of metal-contaminated soils, owing to their high capacity for metal tolerance. Exogenous application of mineral fertilization and the use of microbes and chelating agents increase metal solubility and availability for plant uptake in soil. Also, good agronomic practices such as co-planting of R. communis with other leguminous crops enhance R. communis growth and metal tolerance, thereby improving remediation of metal-contaminated soils. This review, therefore, critically discusses the recent approaches in using R. communis to remediate metal-contaminated soils.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Evaluation on High-yield Cross Combination of Ricinus communis L. Suitable for Mechanical Harvest

【Objective】A joint evaluation on Ricinus communis cross combinations was conducted to provide a theoretical reference for screening high-yield varieties suitable for mechanical harvest.【Method】The yield trait, adaptability for mechanical harvest and photosynthetic performance of 30 R. communis cross combinations were jointly evaluated by grey relational analysis, principal component analysis and cluster analysis.【Result】In the grey relational analysis, 6 combinations including N19 (0.768), N7 (0.751), N11 (0.727), N10 (0.717), N6 (0.713) and N13 (0.712) with weighted correlation degree between various combinations and the ideal varieties were screened out. Among which, the former 4 combinaitons had higher weighted correlation degrees than that in Zibi 5 (0.714), and the weighted correlation degrees of the latter 2 were close to that in Zibi 5. Principal analysis results showed that, 10 traits were classified into 3 principal components, namely, plant type factor, yield determining factor and photosynthetic and branching angle factor, with a cumulative contribution rate of 67.07%. Among the 30 combinations, the comprehensive scores of 21 combinations were higher than that of Zibi 5 (-0.699), and only 4 combinations, N18 (2.370), N4 (1.848), N19 (1.742) and N11 (1.019) had comprehensive scores larger than 1, of which N19 was the most prominent with a much higher score than that in other 3 combinations. Cluster analysis revealed that, the 30 combinations could be classified into 4 groups at Euclidean distance value equal to 22. Among them, Group IV members (including N19, N11 and N30) with the best overall performance was most similar to the ideal varieties based on the average performance in each cluster, however, the branching angle (59.10°) was large and still expected to be improved.【Conclusion】Based on the above 3 evaluation results, the comprehensive evaluation avoids the acceptance of redundant germplasm and the loss of elite germplasm. The N19 and N11 with high yield, good plant type and high photosynthetic rate were selected as the optimal Ricinus communis cross combinations, and their comprehensive performances were better than that of Zibi 5, providing a direction for further improvement of varieties.out of varieties

Solar Radiation-Associated Adaptive SNP Genetic Differentiation in Wild Emmer Wheat, Triticum dicoccoides.

Whole-genome scans with large number of genetic markers provide the opportunity to investigate local adaptation in natural populations and identify candidate genes under positive selection. In the present study, adaptation genetic differentiation associated with solar radiation was investigated using 695 polymorphic SNP markers in wild emmer wheat originated in a micro-site at Yehudiyya, Israel. The test involved two solar radiation niches: (1) sun, in-between trees; and (2) shade, under tree canopy, separated apart by a distance of 2-4 m. Analysis of molecular variance showed a small (0.53%) but significant portion of overall variation between the sun and shade micro-niches, indicating a non-ignorable genetic differentiation between sun and shade habitats. Fifty SNP markers showed a medium (0.05 ≤ FST ≤ 0.15) or high genetic differentiation (FST > 0.15). A total of 21 outlier loci under positive selection were identified by using four different FST -outlier testing algorithms. The markers and genome locations under positive selection are consistent with the known patterns of selection. These results suggested that genetic differentiation between sun and shade habitats is substantial, radiation-associated, and therefore ecologically determined. Hence, the results of this study reflected effects of natural selection through solar radiation on EST-related SNP genetic diversity, resulting presumably in different adaptive complexes at a micro-scale divergence. The present work highlights the evolutionary theory and application significance of solar radiation-driven natural selection in wheat improvement

Solar Radiation-Associated Adaptive SNP Genetic Differentiation in Wild Emmer Wheat, Triticum dicoccoides

Whole-genome scans with large number of genetic markers provide the opportunity to investigate local adaptation in natural populations and identify candidate genes under positive selection. In the present study, adaptation genetic differentiation associated with solar radiation was investigated using 695 polymorphic SNP markers in wild emmer wheat originated in a micro-site at Yehudiyya, Israel. The test involved two solar radiation niches: (1) sun, in-between trees; and (2) shade, under tree canopy, separated apart by a distance of 2–4 m. Analysis of molecular variance showed a small (0.53%) but significant portion of overall variation between the sun and shade micro-niches, indicating a non-ignorable genetic differentiation between sun and shade habitats. Fifty SNP markers showed a medium (0.05 ≤ F(ST) ≤ 0.15) or high genetic differentiation (F(ST) > 0.15). A total of 21 outlier loci under positive selection were identified by using four different F(ST)-outlier testing algorithms. The markers and genome locations under positive selection are consistent with the known patterns of selection. These results suggested that genetic differentiation between sun and shade habitats is substantial, radiation-associated, and therefore ecologically determined. Hence, the results of this study reflected effects of natural selection through solar radiation on EST-related SNP genetic diversity, resulting presumably in different adaptive complexes at a micro-scale divergence. The present work highlights the evolutionary theory and application significance of solar radiation-driven natural selection in wheat improvement