PNNL

Abstract

The plant growth-promoting rhizobacteria (PGPR) on the plant host surface play a key role in biological control and pathogenic response in plant functions and growth. However, it is difficult to elucidate the PGPR effect on plants. Such information is important in biomass production and conversion. Brachypodium distachyon (Brachypodium), a genomics model for bioenergy and native grasses, was selected as a C3 plant model; and the Gram-negative Pseudomonas fluorescens SBW25 (P.) and Gram-positive Arthrobacter chlorophenolicus A 6 (A.) were chosen as a model. The PGPRs were introduced to the Brachypodium seed’s brush sections prior to germination, and their effects on the seeding potential were studied using different modes of time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements, including high mass resolution spectral collection, delayed image extraction, and depth profiling, to study the effect of PGPR on the seed as hosts. Key plant metabolic products and biomarkers, such as flavonoids, phenolic compounds, fatty acids, and auxin indole-3-acetic acid (IAA), were observed in the seed brush sections. Furthermore, principal component analysis (PCA) and two-dimensional (2D) imaging analysis reveal that the seed brush section is sensitive to PGPR compared to the other part of the seed, leading to chemical composition and morphology changes on the seed surface. Our results show that ToF-SIMS can be an effective tool to probe cell-to-cell interactions at the biointerface in the rhizosphere, providing a new approach to study the PGPR effects on seed brush and assess the growth potential of plants.