Transcriptome analysis of Phelipanche aegyptiaca seed germination mechanisms stimulated by fluridone, TIS108, and GR24.

P. aegyptiaca is one of the most destructive root parasitic plants worldwide, causing serious damage to many crop species. Under natural conditions P. aegyptiaca seeds must be conditioned and then stimulated by host root exudates before germinating. However, preliminary experiments indicated that TIS108 (a triazole-type inhibitor of strigolactone) and fluridone (FL, an inhibitor of carotenoid-biosynthesis) both stimulated the germination of P. aegyptiaca seeds without a water preconditioning step (i.e. unconditioned seeds). The objective of this study was to use deep RNA sequencing to learn more about the mechanisms by which TIS108 and FL stimulate the germination of unconditioned P. aegyptiaca seeds. Deep RNA sequencing was performed to compare the mechanisms of germination in the following treatments: (i) unconditioned P. aegyptiaca seeds with no other treatment, (ii) unconditioned seeds treated with 100 mg/L TIS108, (iii) unconditioned seeds treated with 100 mg/L FL + 100 mg/L GA3, (iv) conditioned seeds treated with sterile water, and (v) conditioned seeds treated with 0.03 mg/L GR24. The de novo assembled transcriptome was used to analyze transcriptional dynamics during seed germination. The key gene categories involved in germination were also identified. The results showed that only 119 differentially expressed genes were identified in the conditioned treatment vs TIS108 treatment. This indicated that the vast majority of conditions for germination were met during the conditioning stage. Abscisic acid (ABA) and gibberellic acid (GA) played important roles during P. aegyptiaca germination. The common pathway of TIS108, FL+GA3, and GR24 in stimulating P. aegyptiaca germination was the simultaneous reduction in ABA concentrations and increase GA concentrations. These results could potentially aid the identification of more compounds that are capable of stimulating P. aegyptiaca germination. Some potential target sites of TIS108 were also identified in our transcriptome data. The results of this experiment suggest that TIS108 and FL+GA3 could be used to control P. aegyptiaca through suicidal germination.

[Relationships of soil microbial biomass with soil environmental factors in Tarim Desert highway shelter-forest].

By using correlation analysis, this paper studied the relationships of soil microbial quantity and biomass with soil physical and chemical factors and enzyme activities in highway shelter-forests of Tarim Desert, aimed to approach the interactions between microbes and environmental factors in aeolian sandy soil of extremely arid area. The results showed that soil microbial quantity and biomass in the shelter-forests had an increasing trend with the decrease of soil bulk density and particle size (R < -0.84) and the increase of soil moisture content and porosity (R > 0.85), with the correlation between soil microbial biomass and soil bulk density as the key. Soil microbial quantity and biomass were positively correlated with soil nutrient contents, mainly caused by the correlations of soil actinomycetes and microbial biomass C and P with soil available nutrients. Greater differences (R = 0.51-0.91) were observed in the correlations of soil enzyme activities with soil microbial quantity and biomass, which was mainly determined by the correlations of soil invertase and phosphatase activities with soil actinomycetes and microbial biomass C. The increase of soil salt content was not favorable to the accumulation of soil microbial biomass (R < -0.71), and there was a higher positive correlation (R > 0.63) between soil microbial amount and biomass. In practice, good soil condition should be established in the forestlands of arid area for the development of soil microbes and the promotion of soil matter cycling.