Bacillus subtilis PTA-271 Counteracts Botryosphaeria Dieback in Grapevine, Triggering Immune Responses and Detoxification of Fungal Phytotoxins

Abstract

Plant pathogens have evolved various strategies to enter hosts and cause diseases. Particularly Neofusicoccum parvum, a member of Botryosphaeria dieback consortium, can secrete the phytotoxins (-)-terremutin and (R)-mellein during grapevine colonization. The contribution of phytotoxins to Botryosphaeria dieback symptoms still remains unknown. Moreover, there are currently no efficient control strategies of this disease, and agro-environmental concerns have raised increasing interest in biocontrol strategies to limit disease spread in vineyards, especially by using some promising beneficial bacteria. Here, we first examined in planta the biocontrol capacity of Bacillus subtilis PTA-271 against N. parvum Np-Bt67 strain producing both (-)-terremutin and (R)-mellein. We then focused on the direct effects of PTA-271 on pathogen growth and the fate of pure phytotoxins, and explored the capacity of PTA-271 to induce or prime grapevine immunity upon pathogen infection or phytotoxin exposure. Results provided evidence that PTA-271 significantly protects grapevine cuttings against N. parvum and significantly primes the expression of PR2 (encoding a β-1,3-glucanase) and NCED2 (9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis) genes upon pathogen challenge. Using in vitro plantlets, we also showed that PTA-271 triggers the expression of salicylic acid- and jasmonic acid-responsive genes, including GST1 (encoding a glutathione-S-transferase) involved in detoxification process. However, in PTA-271-pretreated plantlets, exogenous (-)-terremutin strongly lowered the expression of most of upregulated genes, except GST1. Data also indicated that PTA-271 can detoxify both (-)-terremutin and (R)-mellein and antagonize N. parvum under in vitro conditions. Our findings highlight (-)-terremutin and (R)-mellein as key aggressive molecules produced by N. parvum that may weaken grapevine immunity to promote Botryosphaeria dieback symptoms. However, PTA-271 can efficiently attenuate Botryosphaeria dieback by enhancing some host immune responses and detoxifying both phytotoxins produced by N. parvum.

Genome sequence analysis of the beneficial Bacillus subtilis PTA-271 isolated from a Vitis vinifera (cv. Chardonnay) rhizospheric soil: assets for sustainable biocontrol.

“…SA, ET precursor, ABA, PAs, etc …) as well as diverse direct effectors and lytic enzymes against plant pathogens, highlight a big potential valuable for biocontrol strategies. Altogether, plurality of the biomolecules encoded by the genome of B. subtilis PTA-271 appears as strengths that impact both environmental conditions, species ratios and their interactions, enabling to combat a broad spectrum of plant pathogens and the so complex grapevine trunk diseases [3]. Table S1.…”

“…Bene ts of species from the Bacillus group are well described in many sectors of industry, agriculture and viticulture [2]. Focusing on the B. subtilis species, it has been described to provide plants with a broad range of bene ts that include their induced systemic resistance (ISR) upon pathogen attacks, their growth promotion, or the direct control of plant pathogens [3][4][5][6].…”

“…The nutrientacquisition by plants through both the microbiota mineralizing capacity and chelating properties also conditions plant growth and development, as well as volatile compounds derived from bene cial 2.-B. subtilis PTA-271 Genomic sequencing information 2.1.-Genome project history B. subtilis PTA-271 was designated for sequencing because of its e cient capacity to protect grapevine against several pathogens such as Botrytis cinerea or Neofusicoccum parvum, the causal agents of grey mold or Botryosphaeria dieback respectively [3][4][5]. This bene cial microorganism can modulate grapevine defenses, but may also directly antagonize the growth of pathogens and detoxify aggressive molecules.…”

Dissimilar Responses of Ancient Grapevines Recovered in Navarra (Spain) to Arbuscular Mycorrhizal Symbiosis in Terms of Berry Quality

“…Microorganisms accompanying AMF play an important role in the uptake of soil resources as well as on the infectivity and efficiency of AMF isolates [30] and some PGPR, such as Bacillus spp. isolated from vineyards are known to benefit the basal immunity of grapevines against some pathogens [31]. By restoring the bacterial component of the mycorrhizal inoculum in the rhizosphere of the -M plants, differences between -M and +M plants are expected to be mainly due to the presence of AMF associated with +M plants.…”

First molecular insights into the infection process provoked by Neofusicoccum parvum in Liquidambar styraciflua and the identification of new cysteine-rich proteins in both organisms

“…Recently, exogenous application of (R)-mellein and (-)-terremutin in V. vinifera resulted in upregulation of the salicylic acid (SA)-responsive genes PR1 and GST1. In contrast, the expression of jasmonic acid (JA)/ethylene (ET)-responsive genes remained weak or was even downregulated by (-) terremutin [22].…”