Enhanced Iron and Selenium Uptake in Plants by Volatile Emissions of Bacillus amyloliquefaciens (BF06)

Abstract

Volatile organic compounds (VOCs) released by plant growth-promoting rhizobacteria (PGPR) are involved in promoting growth and triggering systemic resistance (ISR) in plants. Importantly, the release of VOCs by some PGPR strains confers improved plant uptake of nutrient elements from the soil. However, the underlying mechanisms of VOCs-regulated nutrient acquisition remain elusive. In this study, VOCs were extracted and identified from Bacillus amyloliquefaciens (strain BF06) using gas chromatography-mass spectrometry (GC-MS). BF06 VOCs exposure significantly promoted the growth and photosynthesis of Arabidopsis plants. To explore how microbial VOCs stimulate growth in plants, gene expression profiles of Arabidopsis seedlings exposed to BF06 VOCs were examined using transcriptomic analyses. In screening differentially expressed genes (DEGs), most upregulated DEGs were found to be related to amino acid transport, iron (Fe) uptake and homeostasis, and sulfate transport. Furthermore, BF06 VOCs significantly enhanced Fe absorption in plants under Fe-limited conditions. However, when nitric oxide (NO) synthesis was inhibited, BF06 VOCs exposure could not substantially augment Fe acquisition in plants under alkaline stress, indicating that VOCs-mediated plant uptake of Fe was required for induction of root NO accumulation. In addition, BF06 VOCs exposure led to a marked increase in some genes encoding for sulfate transporters, and further increased Se accumulation in plants. Intriguingly, BF06 VOCs exposure failed to increase Se uptake in sultr1;2 mutants, which may indicate that high-level transcription of these sulfate transporters induced by BF06 VOCs was essential for enhancing Se absorption by plants. Taken together, our results demonstrated the potential of VOCs released by this strain BF06 to increase Fe and Se uptake in plants.

Bacillus amyloliquefaciens SAY09 Increases Cadmium Resistance in Plants by Activation of Auxin-Mediated Signaling Pathways

“…In nature, soil-borne bacteria can emit diverse kinds of VOCs for overcoming physical constraints of soil matters to reach plant roots, even aboveground tissues of plants, thereby affecting various physiological processes in plants [ 21 ]. It has recently been shown that the production of VOCs by PGPR strains can regulate Fe and selenium (Se) absorption, photosynthesis, and pathogen invasion [ 31 , 32 , 33 , 34 ]. However, whether microbial VOCs induce Cd tolerance of pants and the underlying mechanisms are largely unknown.…”

“…An aliquot of 30 μL of bacterial culture was used to expose plants to VOCs according to the method described by Asari et al [ 40 ]. Moreover, the production of VOCs by SAY09 was identified using gas chromatography (GC)–mass spectrometry (MS) analyses as reported recently by Wang et al [ 34 ].…”

“…Gene ontology (GO) analysis was performed using the Blast2GO program. Differentially expressed genes (DEGs) were identified using the analysis package DEGseq at FDR-adjusted p -value < 0.05, and were assigned to GO term [ 34 ].…”

“…Until now, PGPR have been demonstrated to regulate physiological processes of host plants without physically contacting with plant roots by releasing VOCs [ 31 , 32 , 33 , 34 ]. Recently, the PGPR-emitted VOCs have been taken as novel regulators during plant-microbe interaction [ 35 ].…”

Irrigation Water Quality—A Contemporary Perspective

“…Selenium is known to accumulate in crops grown on soils with high selenium content [161,189], and selenium enrichment has been reported in soils throughout the United States [190]. In their recent study, Wang et al [191] found that volatile organic compounds released by plant growth-promoting rhizobacteria increases both selenium and iron uptake. Uranium is another geogenic, potentially toxic contaminant [192] and studies in nutrient culture show its uptake by crops [193,194].…”