The bHLH transcription factor ILR3 modulates multiple stress responses in Arabidopsis

Abstract

ILR3 and PYE function in a regulatory network that modulates GLS accumulation under iron deficiency. The molecular processes involved in the cross talk between iron (Fe) homeostasis and other metabolic processes in plants are poorly understood. In Arabidopsis thaliana the transcription factor IAA-LEUCINE RESISTANT3 (ILR3) regulates iron deficiency response, aliphatic glucosinolate (GLS) biosynthesis and pathogen response. ILR3 is also known to interact with its homolog, POPEYE (PYE), which also plays a role in Fe response. However, little is known about how ILR3 regulates such diverse processes, particularly, via its interaction with PYE. Since GLS are produced as part of a defense mechanism against wounding pathogens, we examined pILR3::β-GLUCURONIDASE expression and found that Fe deficiency enhances the wound-induced expression of ILR3 in roots and that ILR3 is induced in response to the wounding pathogen, sugarbeet root cyst nematode (Heterodera schachtii). We also examined the expression pattern of genes involved in Fe homeostasis and aliphatic GLS biosynthesis in pye-1, ilr3-2 and pye-1xilr3-2 (pxi) mutants and found that ILR3 and PYE differentially regulate the expression of genes involved these processes under Fe deficiency. We measured GLS levels and sugarbeet root cyst nematode infection rates under varying Fe conditions, and found that long-chain GLS levels are elevated in ilr3-2 and pxi mutants. This increase in long-chain GLS accumulation is correlated with elevated nematode resistance in ilr3-2 and pxi mutants in the absence of Fe. Our findings suggest that ILR3 and PYE function in a regulatory network that controls wounding pathogen response in plant roots by modulating GLS accumulation under iron deficiency.

Transcriptional integration of the responses to iron availability in Arabidopsis by the bHLH factor ILR3

“…New Phytologist repressor of glucosinolate biosynthesis, a class of secondary metabolites conferring resistance against several pathogens, confirming the dual role of ILR3 in regulating genes expression (Li et al, 2014;Samira et al, 2018).…”

The effector GpRbp‐1 of Globodera pallida targets a nuclear HECT E3 ubiquitin ligase to modulate gene expression in the host

“…The degradation of MYB96 attenuates ABA-mediated responses to abiotic stress like drought (Seo et al, 2009). Additionally, transcription factors from different families have been shown to be involved in plant-nematode interactions (Grunewald et al, 2008;Samira et al, 2018;Warmerdam et al, 2019). For example, WRKY23 from Arabidopsis is strongly up-regulated in the early stages of infection by root-knot and cyst nematodes (Grunewald et al, 2008).…”

Genome-wide Survey of the bHLH Super Gene Family in Brassica napus

“…Similarly, members in subfamilies S15 and S26 have been demonstrated to respond to ABA [47,64], while members of the S19 subfamily negatively regulate the BR signaling pathway [67]. Additionally, genes in the S4 subfamily participate in auxin-conjugate metabolism [41,68] (Table 1). Accordingly, our RNA-seq data shows that many BnabHLHs (221, 36.7%) respond to more than one hormone treatment in B. napus roots (Additional file 7: Table S7).…”

“…Regulates the network that controls wounding response in plant roots. Participates in auxin metabolism [41,68]. Act redundantly to positively regulate the deve root hairs [45,46,83].…”