芽孢杆菌WL911促低温下小麦生长效应及其功能基因分析

Bacillus WL911: wheat growth-promoting effects under low temperature and functional genes

摘要:

【背景】青藏高原特殊生境孕育着强耐逆性的微生物资源。【目的】探究青藏高原特殊生境的芽孢杆菌对小麦的促生效应。【方法】以分离自青海省海西蒙古族藏族自治州乌兰县的红柳（Tamarix ramosissima）根围菌株WL911为研究对象进行16S rRNA基因及gyrB基因鉴定；测定其低温适生性；以WL911菌悬液（浓度为1×10⁷ cfu/mL）对4℃条件下的小麦（Triticum aestivum）品种“青麦7号”幼苗进行灌根处理，测定其对小麦幼苗的促生效应；采用二代测序平台Illumina HiSeq×10对菌株WL911进行全基因组测序、功能注释及相关功能基因分析。【结果】菌株WL911鉴定为贝莱斯芽孢杆菌（Bacillus velezensis），可耐受4℃低温；菌株WL911对“青麦7号”幼苗生长具有显著的促生效果，26℃时小麦株高、根长和鲜重分别提高12.22%、50.12%和70.99%；4℃条件下小麦生物量提高的同时，叶绿素含量提高19.72%，H₂O₂、丙二醛（malondialdehyd，MDA）的积累量分别下降23.50%、40.68%，超氧化物歧化酶（superoxide dismutase，SOD）、过氧化物酶（peroxidase，POD）和过氧化氢酶（catalase，CAT）活性分别提高45.82%、17.35%和14.18%；WL911基因组大小为3 915 549 bp，G+C百分含量为46.47%；生物学功能gene ontology （GO）注释到的基因占基因总量的75.74%，包括促生相关功能基因glnB、yclQ和fetB等，可参与合成生长激素、营养元素等途径；存在mnhA、mnhE、pheT、pheS和proV等关键基因参与Na⁺外排机制、编码脯氨酸和酚类化合物等反应；也存在编码冷休克蛋白CspC、CspB和CspD的关键基因cspA。【结论】B.velezensis WL911（登录号为OP874802）是一种优质的生物肥料研发菌株。

Abstract:

[Background] The special habitat of the Qinghai-Xizang Plateau harbors the microbial resources with strong tolerance to stress. [Objective] To explore the wheat (Triticum aestivum) growth-promoting effect of Bacillus in the special habitats of Qinghai-Xizang Plateau. [Methods] The 16S rRNA gene and gyrB of the strain WL911 isolated from the rhizosphere of Tamarix ramosissima in Haixi Mongolian and Tibetan autonomous prefecture, Qinghai province were identified. The tolerance of the strain to low temperature was examined. The growth-promoting effect of the WL911 suspension (concentration of 1×10⁷cfu/mL) on the seedlings of the wheat cultivar ‘Qingmai 7’ at 4℃ was determined. Illumina HiSeq×10 was used for the whole genome sequencing of the strain, which was followed by functional gene annotation and analysis. [Results] The strain WL911 was identified as Bacillus velezensis and could tolerate the low temperature of 4℃. It had a significant growth-promoting effect on the growth of ‘Qingmai 7’ seedlings. At 26℃, the strain increased the plant height, root length, and fresh weight of the seedlings by 12.22%, 50.12%, and 70.99%, respectively. At 4℃, the strain increased the chlorophyll content by 19.72% and decreased the accumulation of H₂O₂ and malondialdehyde by 23.50% and 40.68%, respectively, while increasing the biomass of the seedlings. At the same time, it increased the activities of superoxide dismutase, peroxidase, and catalase by 45.82%, 17.35%, and 14.18%, respectively. The genome size of WL911 was 3 915 549 bp, with the G+C content of 46.47%. The functional genes annotated by gene ontology accounted for 75.74% of the total genes. Specifically, the strain carried growth-promoting genes such as glnB, yclQ, and fetB, which participated in the synthesis of growth hormone and nutrients; it carried mnhA, mnhE, pheT, pheS and proV involved in Na⁺ efflux, proline synthesis, and phenolic compound; and it carried a key gene cspA encoding the cold shock proteins CspC, CspB, and CspD. [Conclusion] B. velezensis WL911 (GenBank accession number:OP874802) serves as a strain for the research and development of high-quality biological fertilizers.