Bacillus circulans GN03 Alters the Microbiota, Promotes Cotton Seedling Growth and Disease Resistance, and Increases the Expression of Phytohormone Synthesis and Disease Resistance-Related Genes

Lijun Qin; Peidong Tian; Qunyao Cui; Shuping Hu; Wei Jian; Chengjian Xie; Xingyong Yang; Hong Shen

doi:10.3389/fpls.2021.644597

Bacillus circulans GN03 Alters the Microbiota, Promotes Cotton Seedling Growth and Disease Resistance, and Increases the Expression of Phytohormone Synthesis and Disease Resistance-Related Genes

Front Plant Sci. 2021 Apr 14:12:644597. doi: 10.3389/fpls.2021.644597. eCollection 2021.

Authors

Lijun Qin^{1

2}, Peidong Tian¹, Qunyao Cui¹, Shuping Hu¹, Wei Jian¹, Chengjian Xie¹, Xingyong Yang¹, Hong Shen^{2

3}

Affiliations

¹ College of Life Sciences, Chongqing Normal University, Chongqing, China.
² Biological Science Research Center, Southwest University, Chongqing, China.
³ College of Resources and Environment Science, Southwest University, Chongqing, China.

Abstract

Plant growth-promoting bacteria (PGPB) are components of the plant rhizosphere that promote plant growth and/or inhibit pathogen activity. To explore the cotton seedlings response to Bacillus circulans GN03 with high efficiency of plant growth promotion and disease resistance, a pot experiment was carried out, in which inoculations levels of GN03 were set at 10⁴ and 10⁸ cfu^⋅mL^-1. The results showed that GN03 inoculation remarkably enhanced growth promotion as well as disease resistance of cotton seedlings. GN03 inoculation altered the microbiota in and around the plant roots, led to a significant accumulation of growth-related hormones (indole acetic acid, gibberellic acid, and brassinosteroid) and disease resistance-related hormones (salicylic acid and jasmonic acid) in cotton seedlings, as determined with ELISA, up-regulated the expression of phytohormone synthesis-related genes (EDS1, AOC1, BES1, and GA20ox), auxin transporter gene (Aux1), and disease-resistance genes (NPR1 and PR1). Comparative genomic analyses was performed between GN03 and four similar species, with regards to phenotype, biochemical characteristics, and gene function. This study provides valuable information for applying the PGPB alternative, GN03, as a plant growth and disease-resistance promoting fertilizer.

Keywords: Bacillus circulans; disease resistance; growth-promoting; phytohormones synthesis; rhizosphere and endophytic microbiota; upland cotton (Gossypium hirsutum L.).