Rhizobacterial volatiles and photosynthesis-related signals coordinate MYB72 in Arabidopsis roots during onset of induced systemic resistance and iron deficiency responses
Plant J. 2015, 84(2):309-322
Zamioudis C, Korteland J, Van Pelt JA, van Hamersveld M, Dombrowski N, Bai Y, Hanson J, Van Verk MC, Ling HQ, Schulze-Lefert P, Pieterse CM


Abstract
In Arabidopsis roots, the transcription factor MYB72 plays a dual role in the onset of rhizobacteria-induced systemic resistance (ISR) and plant survival under conditions of limited iron availability. Previously, it was shown that MYB72 coordinates the expression of a gene module that promotes synthesis and excretion of iron-mobilizing phenolic compounds in the rhizosphere, a process involved in both iron acquisition and ISR signaling. Here, we show that volatile compounds (VOCs) from ISR-inducing Pseudomonas bacteria are important elicitors of MYB72. VOCs-induced MYB72 is co-expressed with the iron uptake-related genes FERRIC REDUCTION OXIDASE 2 (FRO2) and IRON-REGULATED TRANSPORTER 1 (IRT1) in a FER-LIKE IRON DEFICIENCY INDUCED TRANSCRIPTION FACTOR (FIT)-dependent manner, indicating that MYB72 is an intrinsic part of the plants' iron acquisition response that is typically activated upon iron starvation. However, VOCs-induced MYB72 is activated independently of the iron availability in the root vicinity. Moreover, rhizobacterial VOCs-mediated induction of MYB72 requires photosynthesis-related signals, while iron deficiency in the rhizosphere can activate MYB72 in the absence of shoot-derived signals. Together, these results show that the ISR- and iron acquisition-related transcription factor MYB72 in Arabidopsis roots is activated by rhizobacterial volatiles and photosynthesis-related signals, and can enhance the iron acquisition capacity of roots independently of the iron availability in the rhizosphere. This work highlights the role of MYB72 in plant processes by which root microbiota simultaneously stimulate systemic immunity and activate the iron uptake machinery in their host plants. This article is protected by copyright. All rights reserved.

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