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

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.

Key words:Bacillus velezensis;low temperature;growth-promoting effect;functional genes