ABSTRACT
Introduction: Sugarcane endophytic nitrogen-fixing bacterium Klebsiella variícola DX120E displayed broad impact on growth, but the exact biological mechanism, especially polyamines (PAs) role, is still meager. Methods: To reveal this relationship, the content of polyamine oxidase (PAO), PAs, reactive oxygen species (ROS)-scavenging antioxidative enzymes, phytohormones, 1-aminocyclopropane-1-carboxylic synthase (ACS), chlorophyll content, and biomass were determined in sugarcane incubated with the DX120E strain. In addition, expression levels of the genes associated with polyamine metabolism were measured by transcriptomic analysis. Results: Genomic analysis of Klebsiella variícola DX120E revealed that 39 genes were involved in polyamine metabolism, transport, and the strain secrete PAs in vitro. Following a 7-day inoculation period, DX120E stimulated an increase in the polyamine oxidase (PAO) enzyme in sugarcane leaves, however, the overall PAs content was reduced. At 15 days, the levels of PAs, ROS-scavenging antioxidative enzymes, and phytohormones showed an upward trend, especially spermidine (Spd), putrescine (Put), catalase (CAT), auxin (IAA), gibberellin (GA), and ACS showed a significant up-regulation. The GO and KEGG enrichment analysis found a total of 73 differentially expressed genes, involving in the cell wall (9), stimulus response (13), peroxidase activity (33), hormone (14) and polyamine metabolism (4). Discussion: This study demonstrated that endophytic nitrogen-fixing bacteria stimulated polyamine metabolism and phytohormones production in sugarcane plant tissues, resulting in enhanced growth. Dual RNA-seq analyses provided insight into the early-stage interaction between sugarcane seedlings and endophytic bacteria at the transcriptional level. It showed how diverse metabolic processes selectively use distinct molecules to complete the cell functions under present circumstances.
ABSTRACT
Endophytic nitrogen-fixing bacteria are versatile and widely distributed in plants. Numerous strains of endophytic nitrogen-fixing bacteria are used as biofertilizers to minimize the utilization of chemical fertilizers, improve nutrient use efficiency, increase crop productivity, and reduce environmental pollution. However, the mechanism underlying the interaction between nitrogen-fixing bacteria and plants is still unclear. So, the present study was planned to assess the effects of endophytic nitrogen-fixing bacteria on sugarcane by analyzing the changes in physiological and biochemical activities. In the current study, Klebsiella variicola DX120E, an endophytic nitrogen-fixing bacterium, was inoculated on sugarcane varieties B8 and ROC22 to evaluate the effects on nitrogen and carbon metabolism-related enzymatic activity and biomass. Results showed that DX120E inoculation improved the enzymatic activities related to gluconeogenesis and nitrogen metabolism increased the sugarcane plant's height, cane juice Brix, biomass, chlorophyll, and soluble sugar content in sugarcane. Metabolomics analysis revealed that the metabolome modules were highly enriched in carbon and nitrogen metabolic pathways of strain-affected sugarcane than uninoculated control. The identified carbohydrates were associated with the glycolysis or gluconeogenesis and tricarboxylic acid (TCA) cycle in plants. Metabolomic profiling in the present investigation showed that carbohydrate metabolism is coordinated with nitrogen metabolism to provide carbon skeletons and energy to amino acid synthesis, and amino acid degradation results in several metabolites used by the citric acid cycle as an energy source. Moreover, differentially expressed metabolites of non-proteinogenic amino acids have a further complementary role to the action of endophytic nitrogen-fixing bacteria. Meanwhile, a significant difference in metabolites and metabolic pathways present in stems and leaves of B8 and ROC22 varieties was found. This study discovered the potential benefits of DX120E in sugarcane and suggested candidate regulatory elements to enhance interactions between nitrogen-fixing microbes and sugarcane.
ABSTRACT
Objective To investigate the nutrition status of the focus groups of iodine deficiency in the 5 coastal counties(districts)in Guangxi in 2008 to propose corresponding prevention and control measures.Methods In the 5 coastal counties(districts)in Guangxi,including Haicheng,Tieshangang,Yinhai districts and Hepu county in Beihai city,Qinnan district in Qinzhou city,the rates of iodized salt coverage,qualified iodized salt and consumption of qualified iodized salt had always been below the average level of Guangxi.In the study,6 towns were randomly picked in Hepu district,and 3 towns were randomly picked in each of the other 4 coastal counties(districts).Two administrative viRages were randomly picked in each town.Forty children ages 8 to 10 and 10 women of child-beating age from 18 to 42 which included 5 pregnant and lactating women,were picked from each administrative village.Arsenic-cerium catalyzed spectrophotometry(WS/T 107-2006)Was used to determine the urinary iodine.Results In total,1437 urine samples of the children Were picked.The median of the children's urinary iodine Was 191.0μg/L,with 1.4%(20/1437)of the children's urinary iodine<20 μg/L,and 5.4%(77/1437)<50 μg/L, and 20.3%(292/1437) < 100 μg/L. The medians of the children's urinary iodine were 134.5 - 220.0 μg/L.In Haicheng and Hepu, the medians of the children's urinary iodine were higher than 200 μg/L(220.0,209.5 μg/L, respectively). The medians of the children's urinary iodine in the other 3 counties(districts) were within the suitable range between 100 and 200 μg/L(134.5,162.4,199.3 μg/L, respectively). The medians of the 8- and 9-year-old ehildren's urinary iodine (192.3,206.7 μg/L, respectively) were higher than that of the 10-year-old children's(157.2 μg/L, χ2 = 19.644,41.997, all P < 0.017). Totally, 365 urine samples of the women were picked.The medians of the women's urinary iodine in the 5 counties were 88.2 - 195.6 μg/L, with 195.6 μg/L in Haicheng and 156.5 μg/L in Hepu, and 88.2 μg/L in Tieshangang, which was the lowest and below 100 μg/L. The median of the childbearing-age women's urinary iodine was the highest(152.6 μg/L). The median of the lactating women's urinary iodine was the second (131.9 μg/L). The median of the pregnant women's urinary iodine was the lowest (89.4 μg/L) and below 100 μg/L. Only 6.7%(2/30) of the pregnant women's urinary iodine were within the suitable range between 150 and 250 μg,/L. Conclusions In the 5 coastal counties(districts) in Guangxi, 8 to 10-year-old children had good nutrition levels while childbearing-age and lactating women were within the suitable range. As a whole, the pregnant women had insufficient iodine nutrition. We propose that the iodine nutritional status of pregnant women is monitored routinely, with further prevention, control measures, health publicity and education necessary to improve iodized salt coverage.
