Physiological Biochemistry-Combined Transcriptomic Analysis Reveals Mechanism of Bacillus cereus G2 Improved Salt-Stress Tolerance of Glycyrrhiza uralensis Fisch. Seedlings by Balancing Carbohydrate Metabolism

Xiang Xiao; Qiuli Wang; Xin Ma; Duoyong Lang; Zhenggang Guo; Xinhui Zhang

doi:10.3389/fpls.2021.712363

Physiological Biochemistry-Combined Transcriptomic Analysis Reveals Mechanism of Bacillus cereus G2 Improved Salt-Stress Tolerance of Glycyrrhiza uralensis Fisch. Seedlings by Balancing Carbohydrate Metabolism

Front Plant Sci. 2022 Jan 4:12:712363. doi: 10.3389/fpls.2021.712363. eCollection 2021.

Authors

Xiang Xiao¹, Qiuli Wang¹, Xin Ma¹, Duoyong Lang², Zhenggang Guo³, Xinhui Zhang^{1

4}

Affiliations

¹ College of Pharmacy, Ningxia Medical University, Yinchuan, China.
² Laboratory Animal Center, Ningxia Medical University, Yinchuan, China.
³ College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China.
⁴ Ningxia Engineering and Technology Research Center of Hui Medicine Modernization, Ningxia Collaborative Innovation Center of Hui Medicine, Key Laboratory of Ningxia Minority Medicine Modernization, Ministry of Education, Ningxia Medical University, Yinchuan, China.

Abstract

Salt stress severely threatens the growth and productivity of Glycyrrhiza uralensis. Previous results found that Bacillus cereus G2 enhanced several carbohydrate contents in G. uralensis under salt stress. Here, we analyzed the changes in parameters related to growth, photosynthesis, carbohydrate transformation, and the glycolysis Embden-Meyerhof-Parnas (EMP) pathway-tricarboxylic acid (TCA) cycle by G2 in G. uralensis under salt stress. Results showed that G2 helped G. uralensis-accumulating photosynthetic pigments during photosynthesis, which could further increase starch, sucrose, and fructose contents during carbohydrate transformation. Specifically, increased soluble starch synthase (SSS) activity caused to higher starch content, which could induce α-amylase (AM) and β-amylase (BM) activities; increased sucrose content due to the increase of sucrose synthase (SS) activity through upregulating the gene-encoding SS, which decreased cell osmotic potential, and consequently, induced invertase and gene-encoding α-glucosidase that decomposed sucrose to fructose, ultimately avoided further water loss; increased fructose content-required highly hexokinase (HK) activity to phosphorylate in G. uralensis, thereby providing sufficient substrate for EMP. However, G2 decreased phosphofructokinase (PFK) and pyruvate kinase (PK) activities during EMP. For inducing the TCA cycle to produce more energy, G2 increased PDH activity that enhanced CA content, which further increased isocitrate dehydrogenase (ICDH) activity and provided intermediate products for the G. uralensis TCA cycle under salt stress. In sum, G2 could improve photosynthetic efficiency and carbohydrate transformation to enhance carbohydrate products, thereby releasing more chemical energy stored in carbohydrates through the EMP pathway-TCA cycle, finally maintain normal life activities, and promote the growth of G. uralensis under salt stress.

Keywords: Bacillus cereus G2; carbohydrate transformation; glycolysis; photosynthesis; salt stress; tricarboxylic acid cycle.