Avena sativa growth-promoting activity of Bacillus atrophaeus CKL1 under salt stress and the functional genes

Abstract:

[Background] The unique eco-environment in Qinghai province allows the growth of special microbial resources. [Objective] To explore Bacillus resources that can tolerate the plateau environment. [Methods] Antagonistic activity and indole-3-acetic acid (IAA) production of Bacillus atrophaeus CKL1 were determined by plate confrontation and chromogenic method, respectively. Moreover, the low-temperature tolerance and salt resistance of CKL1, as well as the influence of CKL1 on seed germination, seedling growth and the content of chlorophyll, proline, and malondialdehyde of Avena sativa 'Qingyan 1' under salt stress were detected. Then, the whole genome of CKL1 was analyzed by next-generation sequencing and the functional genes were dissected. [Results] CKL1 significantly antagonized Fusarium graminearum and F. acuminatum (inhibition zone diameter >15 mm). The reaction solution of CKL1 and Salkowski reagent turned red and the strain grew in LB medium with 13% NaCl and at 4 ℃, indicating that it could produce IAA and was tolerant to salt and low temperature. CKL1 significantly promoted seed germination and seedling growth of 'Qingyan 1' under salt stress, significantly increased the content of chlorophyll and proline, decreased the content of malondialdehyde, and enhanced the salt resistance of 'Qingyan 1'. The genome of CKL1 was 14 281 280 bp, and 3 303 functional genes were annotated against GO. The genome encodes genes related to the synthesis of lipopeptides iturin and surfactin, and the synthesis of IAA, gene clusters related to the synthesis of osmoregulation substances such as proline and betaine, and the Na⁺/H⁺ antiporter in stress response, as well as the key genes encoding transcriptional regulators involved in response to high salt and low temperature. [Conclusion] The study lays a theoretical basis for using Bacillus to promote the growth of A. sativa under salt stress.