Phylogenetic analysis
The 14 HSFA amino acid sequences of Arabidopsis were retrieved from the TAIR data base. The amino sequence of MtHSFA9 was blasted against the legume transcription factor data base LegumeTFDB (http://legumetfdb.psc.riken.jp/) containing sequences from soybean, M. truncatula and Lotus japonica . The resulting gene list was manually curated to retain only orthologs of the HSFA family. Since the Medicago gene was originally annotated as HSA2.2, we added the amino sequence from two HSFA2 genes already characterized in the literature, TsHSFA2d and OsHSFA2d (Chauhanet al. 2011; Chauhan, Khurana, Agarwal, Khurana & Khurana 2013). This orthologous gene set together with HaHSFA9 was used to construct a phylogenetic tree using neighbour-joining algorithm from the MEGA7.0 software (Kumar, Stecher & Tamura 2016).