磷高效转基因大豆对根际微生物群落的影响

旨在了解转拟南芥紫色酸性磷酸酶基因的磷高效转基因大豆AP15-1的种植对土壤微生物生态的影响。于春秋两季在网室种植转基因大豆AP15-1及其受体YC03-3,在大豆幼苗期、盛花期和成熟期,分别采集根际土和非根际土。平板菌落计数的实验结果显示:AP15-1和YC03-3根际土与非根际土中可培养细菌、真菌和放线菌的数量在不同的季节和不同的生长期是会发生一定的变化,但没有明显的规律;两者根际土间及根际与非根际土间,细菌、真菌和放线菌数量没有明显的差异。BIOLOG生态板实验对碳源代谢特征分析结果显示:同季AP15-1和YC03-3根际土中微生物总体代谢活性要强于非根际土,但AP15-1和YC03-3根际土间及根际与非根际土间,微生物碳代谢活性差异均不显著;并且AP15-1与YC03-3根际土微生物对四大类碳源的代谢也没有明显的偏好。对春秋季成熟期的BIOLOG数据进行生态学丰富度与多样性指数计算分析,也未发现AP15-1和YC03-3根际土及非根际土间存在显著性差异。主成份和聚类分析结果显示:相同季节和相同生长期,AP15-1和YC03-3根际间的差异小于根际与非根际间的差异;季节和大豆生长时期对根际微生物群落造成的影响要大于AP15-1与YC03-3个体差异所产生的影响。研究结果表明转酸性磷酸酶基因的磷高效转基因大豆种植对根际土壤可培养微生物的数量和群落结构没有产生显著的影响。

Effects of P-efficient transgenic soybean on rhizosphere microbial community

Farming is faced with the problems of excessive fertilizer use and the reduction of nutrient use efficiency. Phosphorus is one of the macronutrients necessary for plant growth and development. However, phosphorus is usually immobilized by organic substances or oxidized surfaces of iron-aluminum, and exists in the form of organic or inorganic phosphorus, which makes uptake from most soils difficult. It is well known that acid phosphatase increases the use efficiency of organic phosphorus by releasing inorganic phosphorus from organic phosphorus such as phytate. AtPAP15 encodes a purple acid phosphatase, which has been observed to have phytase activity, in Arabidopsis thaliana. AtPAP15 was over-expressed in transgenic soybean AP15-1 and its expression product was secreted into the rhizosphere because of the presence of a carrot extension gene signal peptide, and thus enhanced use of soil organic phosphorus. Previously, there have not been many reports of research concerning the effects of such nutrient-efficient transgenic plants on soil ecology. In this study, the effects of P-efficient transgenic soybean AP15-1 on soil ecology, especially on the rhizosphere microbial community, were investigated. Transgenic soybean AP15-1 and its receptor YC03-3 were planted in vent-netting greenhouse in 3 m × 5 m experimental plots with three replicates. Soybeans were planted in two successive spring and autumn seasons, and no manure, herbicide or pesticide was used. To ascertain if phytase activity in root exudates of transgenic soybean AP15-1 affects the soil microbe ecosystem, the rhizosphere and non-rhizosphere soil of AP15-1 and its receptor YC03-3 were collected at seedling, florescence and mature developmental stages and analyzed by plate culture count and BIOLOG-EcoPlate. The number of colony forming units (CFU) indicated that the number of culturable bacteria, fungi and actinomyces varied with seasons and development stages. There were no apparent differences in numbers of bacteria, fungi and actinomyces among rhizosphere and non-rhizosphere soil of AP15-1 and YC03-3. The absorbance of BIOLOG-EcoPlate at 590 nm and 750 nm was recorded using microplate spectrophotometer and the average well color development (AWCD) values were calculated. The curves of AWCD versus incubation time showed that the carbon metabolic activity of microbes in rhizosphere soil was higher than that in non-rhizosphere soil from the same season. However, statistical analysis indicated that no significant differences in carbon metabolic activity and carbon source preference were observed among rhizosphere and non-rhizosphere soils of AP15-1 and YC03-3. Statistical analysis of the calculated microbial abundance and diversity index also exhibited no distinct differences among rhizosphere and non-rhizosphere soils of AP15-1 and YC03-3. Principal component and clustering analyses revealed that the difference between the rhizosphere of AP15-1 and YC03-3 was less than that between rhizosphere and non-rhizosphere soil from the same season and at the same plant developmental stage. The effects of season and developmental stage on the community diversity of rhizosphere microbes were greater than that resulting from the genotype differences between AP15-1 and YC03-3. In conclusion, these results demonstrated that the P-efficient transgenic soybean AP15-1 planted in spring and autumn had no significant impact on the soil microbial numbers and community structures.