Volatile compounds from Alcaligenes faecalis JBCS1294 confer salt tolerance in Arabidopsis thaliana through the auxin and gibberellin pathways and differential modulation of gene expression in root and shoot tissues

Abstract

Volatile compounds from rhizobacteria are known to elicit and regulate plant growth and defense against various biotic and abiotic stresses. In the present study, we elucidated the biological role of volatiles from Alcaligenes faecalis strain JBCS1294 on the growth performance of Arabidopsis thaliana under salt stress. JBCS1294 volatiles promoted gains in fresh weight and shoot length of Arabidopsis Col-0 under salt stress by 61.5 and 45.8 %, respectively. Hexanedioic acid and butanoic acid were identified as major volatiles emitted from JBCS1294. However, volatiles from JBCS1294 were unable to induce salt tolerance in eir1 and gai-1 mutant lines of A. thaliana, or in auxin and gibberellin inhibitortreated Col-0 plants. On the other hand, a significant increase of growth in cytokinin-, brassinosteroid-, and ethylene-defective mutant lines, or in respective inhibitortreated Col-0, led us to conclude that the auxin and gibberellin pathways are mediators which confer salt tolerance in Arabidopsis upon introduction of JBCS1294 volatiles. Exposure to JBCS1294 volatiles did not alter proline content in gai-1 and gibberellin inhibitor-treated lines. Additionally, AtNHX1, AtHKT1, AtSOS1, AtAVP1, auxin and brassinosteroid pathway genes were upregulated in the roots after exposure of salt-stressed seedlings to JBCS1294 volatiles, suggesting tissue-specific remodeling of gene expression.

The symbiotic bacteria Alcaligenes faecalis of the entomopathogenic nematodes Oscheius spp. exhibit potential biocontrol of plant‐ and entomopathogenic fungi

“…For instance, Bhattacharyya et al . () identified several VOCs from A. faecalis including butyric acid, propionic acid and benzoic acid, and reported that those VOCs induced tolerance to salt stress in Arabidopsis thaliana by influencing the auxin and gibberellin pathways and upregulating the expression of key ion transporters (Bhattacharyya and Lee, ). In contrast to soluble compounds, volatile organic compounds can diffuse easily through air‐ and gas‐filled pores in the soil and likely play an important role in long‐distance microbial interactions.…”

Adaptation of plants to high-calcium content kart regions: possible involvement of symbiotic microorganisms and underlying mechanisms

“…The VOCs released by Pseudomonadaceae significantly change the expressions of nutrition-storage proteins and γ-gamma-glutamyl hydrolase (Vaishnav et al, 2015). Moreover, a strain of Alcaligenes faecalis, JBCS1294 secretes extracellular adipic acid and butyric acid, which probably influences the synthetic pathway of auxin and gibberellins (Bhattacharyya et al, 2015).…”

Odours from friends and foes: ecological consequences of volatiles from soil-borne fungion plant growth and defence against herbivoress

“…Alternatively, microbial VOCs can change root architecture by increasing root surface area, number of lateral roots and hairs, which in turn facilitate nutrient uptake (Ortiz-Castro et al, 2008;Splivallo et al, 2009;Ditengou et al, 2015;Garnica-Vergara et al, 2015;Casarrubia et al, 2016). (iii) Microbial VOCs can also affect plant hormone homeostasis (Bailly and Weisskopf, 2012;Bhattacharyya et al, 2014), which orchestrates vital plant growth and development (Davies, 2010). These changes in plant hormone homeostasis may be directly linked to plant phenotypic responses to microbial VOCs such as growth promotion through cell expansion (Zhang et al, 2007;Bitas et al, 2015) and cell division (Zhang et al, 2008;Sánchez-López et al, 2016) or changes in root architecture (Splivallo et al, 2009;Garnica-Vergara et al, 2015).…”

“…These changes in plant hormone homeostasis may be directly linked to plant phenotypic responses to microbial VOCs such as growth promotion through cell expansion (Zhang et al, 2007;Bitas et al, 2015) and cell division (Zhang et al, 2008;Sánchez-López et al, 2016) or changes in root architecture (Splivallo et al, 2009;Garnica-Vergara et al, 2015). Therefore, modulation of the hormone-signalling machinery and hormone transport by microbial VOCs can affect plant growth and development (Bailly and Weisskopf, 2012;Bhattacharyya et al, 2014;Tyagi et al, 2018).…”

“…Coined as tolerance (Schafer, 1971), the capability of plants to endure stresses that damage plant tissues or limit plant development can be measured by the degree to which plant growth is affected by a given stress relative to its growth in the undamaged state (Strauss and Agrawal, 1999). Remarkably, microbial VOCs can influence the degree of plant tolerance to abiotic stresses (Bhattacharyya et al, 2014;Liu and Zhang, 2015). For instance, VOCs emitted by Bacillus subtilis can alleviate the negative effects of high salinity or drought on A. thaliana growth by regulating sodium transporters (Zhang et al, 2008) and by closing stomata to prevent water loss, respectively (Cho et al, 2008).…”