A comparative study of microbial community and dynamics of Asaia in the brown planthopper from susceptible and resistant rice varieties.

BACKGROUND

The brown planthopper (BPH) is likely the most destructive, piercing and sucking monophagous insect pest of rice that causes substantial economic losses to farmers. Although yeast-like symbionts (YLS) and virus transmission have been observed in the BPH, the bacterial population inhabiting the BPH has received minimal research attention. Labelling BPH-associated bacterial species may shed light on BPH biology and the interaction between the BPH and rice to provide novel approaches for the efficient control of this insect pest.

RESULTS

We examined RNA-seq results to identify bacterial populations present in different generations of BPHs maintained on susceptible or resistant rice varieties. Overall, 87 operational taxonomic units (OTUs) were determined from the BPH-F0, F6 and F16 generations. These OTUs had Shannon and Simpson index values of 0.37-0.6 and 0.56-1.19, respectively. The evenness values of 0.7-1.00 showed the vastness of the bacterial diversity recovered from the BPH samples. The results showed high species diversity in the BPHs collected from susceptible rice and a high number of members of unclassified bacteria in the BPHs isolated from resistant rice. We noticed that Proteobacteria OTUs were predominant across all samples. Furthermore, PCR data of Asaia species showed variable DNA amplification across the BPH samples collected from susceptible or resistant varieties. The identification of Asaia in BPH eggs and BPH-egg-infected rice revealed its influence on the interaction between the BPH egg and rice.

CONCLUSIONS

The BPHs had clear differences in their microbiomes and in their ability to feed on different rice hosts. These variations could have an essential impact on host adaptation and interaction. These results provide a better understanding of the bacterial diversity and interaction of the microbiome of different generations of BPHs. Furthermore, PCR data of Asaia sp. variation across the BPH samples (isolated from different host genotypes selected from the field and laboratory, including BPH eggs and egg-infected rice tissues), suggest that Asaia could be an important member of the insect microbiome involved in adaptation, its interaction with rice and, most importantly, as a paratransgenic tool for insect control.