Responses of Sorghum Rhizosphere Soil Bacterial Communities to Salt Stress

doi:10.13560/j.cnki.biotech.bull.1985.2023-0685

Abstract

Abstract:

【Objective】This study aims to investigate the changes in the bacterial community structure of sorghum roots under salt stress, as well as the characteristics of the rhizosphere bacterial co-occurrence network structure.【Method】Two sorghum varieties, HN16（salt-sensitive）and GLZ（salt-tolerant）, with varying levels of salt tolerance were cultivated in pots and subjected to salt stress. The root microbiome of these plants was then analyzed using 16S amplicon sequencing technology.【Result】With the aggravation of salt stress, the contents of total phenols and flavonoids in the sorghum roots gradually increased, and the appropriate salt stress induced the synthesis of phenolic acids to improve the salt tolerance of sorghum. The results of the microbial community structure analysis showed that Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes and Chloroflexi were the dominant phyla in sorghum rhizosphere soils. Comparative analysis of samples showed that the bacterial composition of sorghum rhizosphere under salt stress was less affected by growth stage, and the bacterial community structure of sorghum rhizosphere changed with the aggravation of salt stress. Through WGCNA analysis of all filters OTUs, a total of 12 gene co-expression module were identified, pink module had significantly positive correlation with salinity and greenyellow module had significantly positive correlation with period and the contents of total phenols and flavonoids after salt treatment. The bacterial co-occurrence network was more complex in low salt stress soils than in higher salt stress soils, reflected by more nodes and more edges. The 13 network key OTUs were identified, OTU8480, OTU6866, OTU3247 and OTU3499 was the keyOTUs in S0 network; OTU6895, OTU4206, OTU6470, OTU1810 and OTU4916 in S3 network; OTU4217, OTU8426, OTU4847, and OTU6066 were the key OTUs in S7 network. 【Conclusion】The composition of rhizosphere bacteria in both varieties of sorghum has been modified in response to salt stress. After salt stress, with more complex co-occurrence network and tighter connections between OTUs of rhizosphere soil bacterial communities.

Key words: sorghum, rhizosphere, microbial community structure, salt stress

GAO Yu-kun, ZHANG Jian-dong, YANG Pu-yuan, CHEN Dong-ming, WANG Zhi-bo, TIAN Yi-jin, Zakey Eldinn. E. A. Khlid, CUI Jiang-hui, CHANG Jin-hua. Responses of Sorghum Rhizosphere Soil Bacterial Communities to Salt Stress[J]. Biotechnology Bulletin, 2024, 40(4): 203-216.

Figures/Tables 9

Table 1 Effect of salt stress on plant height, TPC and TFC of sorghum roots

指标Items	时期Period	S0	S3	S7
株高 PH/cm	拔节期 E	67.9±6.9a	75.8±3.8a	54.6±4.6b
	开花期 F	115.8±4.3b	135.7±4.2a	92.6±2.6c
	成熟期 M	164±4.6b	185.3±4.1a	136.5±3c
总酚TPC/（mg·100 g^-1）	拔节期 E	60.92±19.04b	243.92±6.03a	209.38±23.76a
	开花期 F	222.89±2.72c	315.09±5.19a	293.09±15.88b
	成熟期 M	240.44±53.08a	285.43±7.59a	250.61±7.81a
总黄酮TFC/（mg·100 g^-1）	拔节期 E	50.5±17.02b	180.46±20.69a	175.15±13.72a
总黄酮TFC/（mg·100 g^-1）	开花期 F	182.05±3.18c	342.78±62.02b	423.93±22.05a
	成熟期 M	208.04±8.17b	273.82±11.18a	220.24±18.35b

Table 2 Sequencing quality of rhizosphere microbial community

样本 Sample	有效序列数目 Seq_num	碱基数 Base_num/bp	样本序列平均长度 Mean_length/nt	样本最短序列长度 Min_length/nt	样本最长序列长度 Max_length/nt
ES0	162 093	67 727 026	417.82	252.00	506.33
ES3	160 893	67 266 875	418.08	244.33	491.67
ES7	172 634	72 184 160	418.14	247.67	486.33
FS0	171 403	71 496 233	417.13	214.33	468.33
FS3	157 105	65 548 212	417.20	271.00	474.00
FS7	161 222	67 470 566	418.48	235.00	490.67
MS0	151 139	63 252 701	418.48	227.00	465.00
MS3	148 582	61 959 724	417.02	247.33	477.00
MS7	146 276	61 086 964	417.61	245.33	471.00

Fig. 1 Evaluation of sequencing results and Alpha diversity analysis of soil bacterial in sorghums soil samples under different treatments A: Rank abundance curve; B: dilution curves; C and D Shannon, Simpson, ACE and Chao1 indices, respectively

Fig. 2 Analysis of sorghum rhizosphere soil samples A: Sample Beta diversity analysis based on PCoA. B: Sample grouping analysis based on PLS-DA

Fig. 3 Bacterial community structure of sorghum rhizosphere A: Flower plot analysis for bacterial species（OTU）of different samples. B: Map of bacterial community structure at the phylum and genus level. C and D indicate phylum and genus distribution among different groups of rhizosphere soils, respectively. *, **, and *** indicate significant differences at the 0.05, 0.01, and 0.001 levels, respectively

Fig. 4 Determination of soft threshold and module division The ordinate of A indicate the scale-free network model index; the ordinate of B indicate the average network connectivity corresponding to each soft threshold; the abscissas of A and B both indicate the soft threshold ; C：OTU modules obtained by dynamic shearing algorithm and after merging similar expression patterns

Fig. 5 Analysis of WGCNA in sorghum rhizosphere bacteria A: Bacterial phylum composition in each module. B: Association analysis of OTUs co-expression network modules with traits. C and D indicate the hub OTUs co-expression network in pink and greenyellow module, respectively

Fig. 6 A phylogenetic tree showing the relationship among salt-treated groups and microbial functional features in salt-treated soil groups via COG analysis A: Evolutionary relationship in rhizosphere soil in four salt-treated soil groups. B: The microbial functional features in three salt-treated soil groups sorghum COG analysis. C: Microbial functional features in salt-treated soil groups via COG analysis based on PCA

Fig. 7 Co-occurrence network in sorghum rhizosphere bacteria A: Network revealing the modular associations among sorghum rhizosphere bacterial Otus. B: Species composition of sorghum rhizosphere bacterial network under different salt stress(phylum level). C: Sorghum rhizosphere bacterial network topological characteristics under different salt stress treatments. D: Distribution of nodes based on their topological roles in modules under different salt stress treatments

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