A comparative morphological and transcriptomic study on autotetraploid Stevia rebaudiana (bertoni) and its diploid.

Stevia rebaudiana is an important medical plant for producing steviol glycosides (SGs) or stevioside. Autotetraploids (4x = 44) show an increasing level of morphology, physiology and tolerances comparing to diploids (2x = 22). However, little information regarded on the comparative transcriptome analysis between diploid and autotetraploid S. rebaudiana was found. In this study, synthetic autotetraploid was induced and morphological features were confirmed. A comprehensive transcriptome of stevia leaf, stem and root from the diploids and autotetraploids was constructed based on RNA-seq, yielded 1,000,892,422 raw reads and subsequently assembled into 251,455 transcripts, corresponded to 146,130 genes. Pairwise comparisons of the six leaf libraries between the diploids and autotetraploids revealed 4114 differentially expression genes (DEGs), in which 2105 (51.17%) were up-regulated in autotetraploids and associated with SGs biosynthesis, plant growth and secondary metabolism. Moreover, weighted gene co-expression network analysis showed co-expressed genes of fifteen genes of SG biosynthesis pathway were enriched in photosynthesis, flavonoid and secondary metabolic process, plant growth and morphogenesis. A hundred of DEGs related to plant resistance were identified by interviewing PlantPReS database. This study has highlighted molecular changes related to SGs metabolism of polyploidy, and advanced our understanding in plant resistance responsible for phenotypic change of autotetraploids.

[Effect of exogenous Ca2+ on protective infection of Pinellia ternata and accumulation of major components under high temperature stress].

OBJECTIVE: To study the effect of exogenous Ca2+ on protective infection of Pinellia ternata and accumulation of major components under high temperature stress. METHOD: The soilless cultivation experiment was applied, stress resistance index of P. ternata leaves, statistics the rate of lodge P. ternata,the content of oxalate in different places in the plant, the content of total alkaloids, total organic acids and glucosine in P. ternata tubers were measured based on different concentrations of exogenous Ca2+. RESULT: The test results showed that, at lower concentrations of Ca2+ treatments, the rate of lodge P. ternata was higher than that of the others. With Ca2+ concentration increasing, activities of SOD and POD initially increased and then decreased, however, proline level tended to be down then up. Soluble oxalic acid content was lower than the content of unhandled treatment in P. ternata leaves and tubers; with Ca2+ concentration increasing, soluble oxalic acidl content and yield showed a tendency of decrease after increase in the leaves and tubers. Compared with other treatments, spraying 400 mg x L(-1) Ca2+ significantly enhanced the accumulation of total alkaloid and guanosine in P. ternata tubers. At Lower concentrations of Ca2+, the content of total free organic acid was higher in the tuber. CONCLUSION: With the treatment of Ca2+ the capacity of heat resistance was improved in P. ternata plants, the rate of lodge P. ternata was postponed, growing period was extended and corresponding production has increased by spraying exogenous Ca2+.

[Selection of the microorganism for dioscin hydrolyze].

OBJECTIVE: To select the microorganism which can hydrolyze dioscin to diosgenin. METHODS: The microorganism were selected from the surface of rhizome, rhizosphere soil, the inside of the leaves and rhizome of Dioscorea zingiberensis C. H. Wright. Diosgenin was identified by thin-layer chromatography and HPLC. RESULTS: The microorganism which could hydrolyze dioscin from the experiment were identified as Aspergillus sp and Alternaria sp. Characteristics of enzymes production and fermentation technology of Aspergillus No. 1 were also studied primarily. CONCLUSION: The Aspergillus strain No. 1 can secret enzyme to hydrolyze dioscin into diosgenin effectively.