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Ethylene-Responsive AP2/ERF Transcription Factor MACD1 Participates in Phytotoxin-Triggered Programmed Cell Death

¹Laboratory of Defense in Plant–Pathogen Interactions, and ²Developmental Regulation Laboratory, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan; ³Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan; ⁴Laboratory of Plant Molecular Biology, and ⁵Laboratory of Plant Pathology, Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, Japan

To investigate plant programmed cell death (PCD), we developed the model system using phytotoxin AAL, which is produced by necrotrophic pathogen Alternaria alternata f. sp. lycopersici, and AAL-sensitive Nicotiana umbratica. We previously reported that ethylene (ET) signaling plays a pivotal role in AAL-triggered cell death (ACD). However, downstream signaling of ET to ACD remains unclear. Here, we show that the modulator of AAL cell death 1 (MACD1), which is an APETALA2/ET response factor (ERF) transcription factor, participates in ACD and acts downstream of ET signaling during ACD. MACD1 is a transcriptional activator and MACD1 overexpression plants showed earlier ACD induction than control plants, suggesting that MACD1 positively regulates factors affecting cell death. To investigate the role of MACD1 in PCD, we used Arabidopsis thaliana and a structural analog of AAL, fumonisin B1 (FB1). FB1-triggered cell death was compromised in ET signaling and erf102 mutants. The loh2 mutants showed sensitivity to AAL, and the loh2-1/erf102 double mutant compromised ACD, indicating that ERF102 also participates in ACD. To investigate the PCD-associated genes regulated by ERF102, we compared our microarray data using ERF102 overexpression plants with the database of upregulated genes by AAL treatment in loh2 mutants, and found genes under the control of ERF102 in ACD.