Different Roles of Beauveria bassiana Bbchitinase 1 and Bbchitinase 2 in Host Infection

doi:10.3969/j.issn.1000-2561.2021.04.027

Abstract

Abstract:

Two extracellular chitinases were secreted by Beauveria bassiana during the infection process, named as Bbchitinase 1 and Bbchitinase 2, but the roles were not clear yet. The correlation analysis between chitinase activity and virulence, correlation analysis between gene expression level and virulence, bioinformatics analysis and expression patterns assay were performed in this paper in order to clarify different roles of Bbchitinase 1 and Bbchitinase 2. Statistical analysis and inhibition test showed that extracellular chitinase activitiy was positively correlated with the virulence, while the expression levels of Bbchitinase 1 and Bbchitinase 2 were different in strains. The expression level of Bbchitinase 1 was positively correlated with the virulence of the strains (MMT and LT₅₀); meanwhile, there was no significant relationship between Bbchitinase 1 and virulence of the strains. In addition, the bioinformatics analysis showed that there were significant differences in structure and function of Bbchitinase 1 and Bbchitinase 2, which might combine with different ligands and participate in different metabolic processes. Furthermore, the spatiotemporal expression pattern analysis showed that Bbchitinase 1 was significantly up-regulated only in the formation of penetration peg and penetration of perisoma stage of infection, meanwhile Bbchitinase 2 was slightly up-regulated in the formation of blastospore stage and significantly up-regulated in the mycelial vegetative growth stage. The results suggested that Bbchitinase 1 might be involved into body wall penetration at early infection stage and had positive correlation with virulence, while Bbchitinase 2 into the proliferation and metabolism of mycelium at the later infection stage. The results of this study clarified the role of different chitinases in the infection process of B. bassiana, and established a mathematical model to determine the virulence of B. bassiana based on the expression level of Bbchitinase 1 gene, which provides the important scientific basis for screening of high toxicity and high stability biocontrol strains and great significance for improving the application effect of green ecological control.

Key words: Beauveria bassiana, virulence factor, chitinase, Bombyx mori

CLC Number:

S476.12

WANG Yongsong, GENG Tao, LU Fuping, WU Huazhou, LOU Dezhao, TU Nana, WANG Shuchang. Different Roles of Beauveria bassiana Bbchitinase 1 and Bbchitinase 2 in Host Infection[J]. Chinese Journal of Tropical Crops, 2021, 42(4): 1092-1098.

Figures/Tables 9

Tab. 1 MMT, LT50 and 95% confidence intervals of strains

菌株 Strains	MMT /h	MMT 95% 置信区间 MMT 95% confidence interval/h	LT₅₀ /h	LT₅₀ 95 % 置信区间 LT₅₀95% confidence interval/h
Bbcaasipp-Hv	35.12	33.28~36.74	55.61	52.37~58.13
Bbcaasipp-Lv	75.46	73.81~77.57	94.49	91.62~98.91
HN6	45.15	42.33~46.85	73.80	71.06~76.79
BbMQ-04	48.13	45.18~51.02	77.47	75.13~80.05
B8	55.54	51.85~58.34	82.54	78.22~85.23
BbMQ-09	62.52	60.17~65.33	88.18	83.78~93.79

Tab. 2 Total extracellular chitinase activity in different

菌株 Strains	Bbcaasipp-Hv	Bbcaasipp-Lv	HN6	BbMQ04	BbMQ09	B8
总几丁质酶活性	22.3	15.1	22.8	17.6	19.8	12.3

Fig. 1 Change in MMT and LT50 after treated with Allosamidin A: Bbcaasipp-Hv; B: Bbcaasipp-Lv; C: HN6; D: BbMQ-04; E: B8; F: BbMQ-09; * means T-test shows significant difference (t=6 h, P<0.05).

Fig. 2 Regression equation analysis of MMT, LT50 and extracellular chitinases activities Each “○” is the MMT value of a strain; SE is the standard error; R2 is the correlation coefficient.

Fig. 3 Relative expression levels of Bbchitinase 1 and Bbchitinase 2

Fig. 4 Correlation between MMT, LT50 and relative expression of Bbchitinase 1 A: MMT; B: LT50. R2 is the correlation coefficient.

Fig. 5 Phylogenetic analysis of Bbchitinase 1 and Bbchitinase 2

Fig. 6 Tertiary structure of Bbchitinase 1 and Bbchitinase 2

Fig. 7 Expression pattern of Bbchitinase 1 and Bbchitinase 2 upon B. bassiana infection in B. mori A: Bbchitinase 1; B: Bbchitinase 2; * means T-test shows significant difference (t=6 h, P<0.05).

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