Significant variations of bacterial communities among the developmental stages of Scirpophaga incertulas (Walker) (Lepidoptera: Crambidae)

Abstract

The yellow stemborer, Scirpophaga incertulas, is a monophagous pest of rice, attacking the crop from its vegetative to reproductive stages. Microorganisms are crucial in influencing the insect's life cycle, evolution, and ecology, presenting an avenue for understanding and improving management strategies. Present research employed advanced next-generation sequencing technology to investigate the microbiota of S. incertulas, a previously unexplored area for developmental stage associated microbial diversity. The study used 16 S rRNA V3-V4 region amplicon sequencing to determine the diversity of bacteria associated with different developmental stages of S. incertulas. Taxonomically, bacterial communities were classified into 25 phyla, encompassing 46 classes, 101 orders, 197 families, and 364 genera. The major phyla identified were Proteobacteria (39%), Firmicutes (39%), Actinobacteria (11%), and Bacteroidetes (7%), with Proteobacteria being the most predominant across all developmental stages except the larval stage, where Firmicutes took precedence. Moraxellaceae, Bacillaceae, Xanthomonadaceae, Sphingobacteriaceae, and Flavobacteriaceae were predominant families across all the developmental stages. However, in the egg and adult stages, the abundance of Bacillaceae was notably lower, whereas Prevotellaceae found significantly higher in adult stages. Dominant genera across all stages included Acinetobacter, Bacillus, Lactobacillus, Enterococcus, and Pseudomonas. The result showed that the highest number of Operational Taxonomic Units (OTUs) were in the larval stage (426 OTUs), the lowest in adults (251 OTUs), and the egg stage (254 OTUs). This suggests that the microbiota may play a role in the growth and development of S. incertulas. The predicted functional assessment of the associated S. incertulas microbiota revealed that the microbiota primarily participated in metabolic pathways, secondary metabolite biosynthesis, energy metabolism, signaling, and cellular processes. Our findings shed light on the significant variations in the microbial community and their predicted functions present in S. incertulas across developmental stages. The present study findings will help in developing novel microbiota-based management strategies.

Keywords: Cereals; Insects; Microbes; Molecular; Moraxellaceae; Proteobacteria.

Fig. 1

The phyla percentage distribution of the 51 common strain-level shared OTUs across all developmental stages (A, B).

Fig. 2

A box plot illustrating the bacterial community’s alpha diversity indices (A) ACE index; (B) Chao1 index; (C) Shannon index; (D) Simpson index; and (E) Fisher index) at different developmental stages of N. lugens. The different letters (a, b, c, d) on box plots indicate a significant difference (p < 0.05) and the same letters indicate no significant difference (p > 0.05) among the developmental stages using the Kruskal-Wallis H test.

Fig. 3

The phylum-level distribution and relative abundance (%) of the bacterial population associated with Scirpophaga incertulas at various developmental stages. ES: egg stage; LS: larval stage (1–5th instars); PS: pupal stage; AS: adult stage.

Fig. 4

Heatmap illustrates the family-level relative abundance of 16 S rRNA gene OTUs at various developmental stages. The developmental stages of S. incertulas shown are the egg stage, larval stage, pupa stage, and adult stage (ES, LS, PS, and AS).

Fig. 5

The average difference of bacterial families among the egg and other stages of development with p values < 0.05 (Welch’s t-test, FDR adjusted).

Fig. 6

The average difference of bacterial families among the adult and other stages of development with p values < 0.05 (Welch’s t-test, FDR adjusted).