Ecological impacts of human thioredoxin expression and interspecific hybridization on the soybean rhizosphere microbiome: insights from ASV-level niche analysis

Abstract

Genetically modified (GM) soybean (Glycine max) expressing a human thioredoxin (trx) gene under the control of a seed-specific promoter has been developed for cosmetic applications, but its ecological effects remain poorly understood. We examined the rhizosphere microbiomes of GM soybean, wild soybean (Glycine soja), and F3 interspecific hybrids segregating for the transgene under low-input field conditions. Rhizosphere soil samples were collected at the vegetative and flowering stages, and microbial communities were analyzed via high-throughput sequencing of 16S rRNA and ITS regions. This study represents the first application of amplicon sequence variant (ASV)-level niche breadth analysis to evaluate the rhizosphere effects of a trx-expressing GM soybean. ASV-level analysis and ecological niche breadth classification revealed that genotype-specific microbial shifts were not apparent at relatively high taxonomic levels. Notably, several bacterial ASVs from the class Bacilli were more abundant in GM and homozygous plants at flowering. A fungal ASV from Tausonia also showed increased abundance in the GM lines. These findings highlight that genotype-driven microbial shifts can occur in a stage-specific manner and underscore the importance of fine-resolution microbial analyses in environmental risk assessment.