Harpin-inducible defense signaling components impair infection by the ascomycete Macrophomina phaseolina

Abstract

Soybean (Glycine max) infection by the charcoal rot (CR) ascomycete Macrophomina phaseolina is enhanced by the soybean cyst nematode (SCN) Heterodera glycines. We hypothesized that G. max genetic lines impairing infection by M. phaseolina would also limit H. glycines parasitism, leading to resistance. As a part of this M. phaseolina resistance process, the genetic line would express defense genes already proven to impair nematode parasitism. Using G. max, exhibiting partial resistance to M. phaseolina, experiments show the genetic line also impairs H. glycines parasitism. Furthermore, comparative studies show G. max exhibits induced expression of the effector triggered immunity (ETI) gene NON-RACE SPECIFIC DISEASE RESISTANCE 1/HARPIN INDUCED1 (NDR1/HIN1) that functions in defense to H. glycines as compared to the H. glycines and M. phaseolina susceptible line G. max. Other defense genes that are induced in G. max include the pathogen associated molecular pattern (PAMP) triggered immunity (PTI) genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), NONEXPRESSOR OF PR1 (NPR1) and TGA2. These observations link G. max defense processes that impede H. glycines parasitism to also potentially function toward impairing M. phaseolina pathogenicity. Testing this hypothesis, G. max genetically engineered to experimentally induce GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 expression leads to impaired M. phaseolina pathogenicity. In contrast, G. max engineered to experimentally suppress the expression of GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 by RNA interference (RNAi) enhances M. phaseolina pathogenicity. The results show components of PTI and ETI impair both nematode and M. phaseolina pathogenicity.

The heterologous expression of a soybean (Glycine max) xyloglucan endotransglycosylase/hydrolase (XTH) in cotton (Gossypium hirsutum) suppresses parasitism by the root knot nematode Meloidogyne incognita

“…Harpin was shown to induce the expression of homologs of NDR1, specific MAPKs, NPR1 and XTH43, among other genes in the G. max-H. glycines pathosystem [14,39,40]. The induction of NDR1 can function in G. max on different pathogens, including the charcoal rot ascomycete (Macrophomina phaseolina), indicating a broad effectiveness for different types of pathogens [50]. Heterologous expression approaches were also used to examine these G. max genes in G. hirsutum to determine early signaling events that are transduced either through pathogen effectors (harpin), membrane receptors (NDR1), or transcription factors (NPR1) [14,[38][39][40].…”

The Glycine max Conserved Oligomeric Golgi (COG) Complex Functions During a Defense Response to Heterodera glycines

“…COG gene-specific primers are used in PCR reactions to confirm the presence of the targeted gene (Supplementary Table 1). The COG gene-containing pRAP15/17 destination vectors undergo transformation into chemically competent Agrobacterium rhizogenes K599 (K599) using the freeze-thaw transformation procedure (Hofgen and Willmitzer, 1988;Haas et al, 1995;Collier et al, 2005;Lawaju et al, 2018).…”

“…Transgenic plants have been generated according to Lawaju et al (2018). The 250-ml culture of K599 that is transformed with the COG-containing plasmid is pelleted through centrifugation in a Sorvall RC6 Plus Superspeed Centrifuge at 4 o C for 20 min.…”

“…The determination of the extent of COG gene expression in transgenic G. max is accomplished by RT-qPCR according to Lawaju et al (2018). The analysis procedure uses Taqman 6-carboxyfluorescein (6-FAM)-labeled probes and Black Hole Quencher (BHQ1) (MWG Operon) ( Supplementary Table 1) according to the manufacturer's instructions.…”

“…Heterodera glycines infections of transgenic plants are performed according to the procedures described in Lawaju et al (2018). H. glycines [NL1−Rhg/HG−type 7/race 3] eggs are obtained from cysts, collected from 60-day-old greenhouse-grown G. max stock plants grown in 500-cm 3 polystyrene pots.…”