Long-Lasting Primed State in Maize Plants: Salicylic Acid and Steroid Signaling Pathways as Key Players in the Early Activation of Immune Responses in Silks

Abstract

In the present study, we investigated the induced systemic resistance (ISR) activated by the beneficial fungus Trichoderma atroviride in maize plants, and the early immunological responses triggered after challenge with the ear rot pathogen Fusarium verticillioides. By transcriptional analysis, we were able to identify the gene core set specifically modulated in silks of maize plants expressing ISR. Our results showed that the main transcriptional reprogramming falls into genes involved in five main functional categories: cell structure or cell wall, amino acid and protein metabolism, stress responses, signaling, and transport. Among these ISR-related genes, it is important to highlight novel findings regarding hormone metabolism and signaling. The expression of hormone-dependent genes was in good agreement with the abscisic acid, jasmonic acid, and salicylic acid (SA) levels detected in the plants under study. The experimental design allowed the identification of novel regulatory elements related to a heightened state of defense in silks and suggests that steroids and SA are central components of a master regulatory network controlling the immunity of silks during ISR. The results presented also provide evidence about the molecular mechanisms used by maize silks against F. verticillioides to counteract pathogenic development and host invasion, including pathogenesis-related genes, plant cell-wall reinforcement, fungal cell-wall-degrading enzymes and secondary metabolism.

Analysis of the transcriptomic, metabolomic, and gene regulatory responses to Puccinia sorghi in maize

“…We constructed a complex GRN (Figure 7) and identified several potential hub TFs, which are obvious candidates for subsequent in planta validation. The WRKY TF family plays crucial roles in the response to biotic stresses in a wide range of plant species (Agostini et al., 2019; Liu et al., 2019; Wei et al., 2012; Yu et al., 2018). Several WRKY TFs were identified upstream in the resistance‐specific GRN at both 12 and 24 hpi, the most significant of these being WRKY53 (Figure 7).…”

Genomics of Maize Resistance to Fusarium Ear Rot and Fumonisin Contamination

“…As the down-regulation of ZmLOX3 , a known susceptibility factor, was recently reported as a mechanism behind Trichoderma virens -mediated induced systemic resistance [ 101 ], studies of induced systemic resistance (ISR) activated by beneficial fungus could be also a valuable resource to expose hidden molecular mechanisms essential to reduce disease development. In that sense, the study of ISR activated by the beneficial fungus T. atroviride in maize plants that were posteriorly inoculated with F. verticillioides have provided evidence of the role of pathogenesis-related, plant cell-wall reinforcement, fungal cell-wall-degrading enzymes, and secondary metabolism in maize immune response to F. verticillioides [ 102 ].…”

Transcriptome Analysis Identified Core Genes Involved in Maize Resistance to Rhizoctonia Solani

“…Four of them have been reported to be involved in maize defense response. For example, ZmbZIP111 was upregulated during the induced systemic resistance activation by Trichoderma atroviride [25], while ZmNAC41 was transcriptionally induced by the hemibiotrophic ascomycete fungus Colletotrichum graminicola [26]. ZmJMJ22 was identi ed to confer resistance to maize rough dwarf disease [27].…”