Distinct gene expression and secondary metabolite profiles insuppressor of prosystemin-mediated responses2 (spr2)tomato mutants having impaired mycorrhizal colonization

Abstract

Arbuscular mycorrhizal fungi (AMF) colonization, sampled at 32-50 days post-inoculation (dpi), was significantly reduced in suppressor of prosysteminmediated responses2 (spr2) mutant tomato plants impaired in the ω−3 FATTY ACID DESATURASE7 (FAD7) gene that limits the generation of linolenic acid and, consequently, the wound-responsive jasmonic acid (JA) burst. Contrary to wild-type (WT) plants, JA levels in root and leaves of spr2 mutants remained unchanged in response to AMF colonization, further supporting its regulatory role in the AM symbiosis. Decreased AMF colonization in spr2 plants was also linked to alterations associated with a disrupted FAD7 function, such as enhanced salicylic acid (SA) levels and SA-related defense gene expression and a reduction in fatty acid content in both mycorrhizal spr2 roots and leaves. Transcriptomic data revealed that lower mycorrhizal colonization efficiency in spr2 mutants coincided with the modified expression of key genes controlling gibberellin and ethylene signaling, brassinosteroid, ethylene, apocarotenoid and phenylpropanoid synthesis, and the wound response. Targeted metabolomic analysis, performed at 45 dpi, revealed augmented contents of L-threonic acid and DL-malic acid in colonized spr2 roots which suggested unfavorable conditions for AMF colonization. Additionally, timeand genotype-dependent changes in root steroid glycoalkaloid levels, including tomatine, suggested that these metabolites might positively regulate the AM symbiosis in tomato. Untargeted metabolomic analysis demonstrated that the tomato root metabolomes were distinctly affected by genotype, mycorrhizal colonization and colonization time. In conclusion, reduced AMF colonization efficiency in spr2 mutants is probably caused by multiple and interconnected JA-dependent and independent gene expression and metabolomic alterations.How to cite this article Casarrubias-Castillo K, Montero-Vargas JM, Dabdoub-González N, Winkler R, Martinez-Gallardo NA, Zañudo-Hernández J, Avilés-Arnaut H, Délano-Frier JP. 2020. Distinct gene expression and secondary metabolite profiles in suppressor of prosystemin-mediated responses2 (spr2) tomato mutants having impaired mycorrhizal colonization. PeerJ 8:e8888 . 2012. Loss of function of fatty acid desaturase 7 in tomato enhances basal aphid resistance in a salicylate-dependent manner.

Development and Yield Traits Indicate That the Constitutive Wound Response Phenotype of Prosystemin Overexpressing Tomato Plants Entails No Fitness Penalty

“…The RNA extraction procedure was performed as described previously [61]. Briefly, total RNA was extracted from frozen root and leaf tissues using a modified method based the use of the Trizol reagent (Invitrogen, Carlsbad, CA, USA).…”

Deciphering mechanisms underlying Mycorrhizal Induced Resistance in tomato plants

“…Several studies have shown the transcriptional reprogramming that takes place in mycorrhizal colonized roots, which affects both the primary and secondary metabolism. This association has a considerable impact in different pathways related to phytohormones, nutrient transport, defensive responses or plant development (Hohnjec et al, 2005;Fiorilli et al, 2009;Vangelisti et al, 2018;Casarrubias-Castillo et al, 2020).…”