*4.1. Identification and Annotation of GmWRKYs Response to Drought/Salt Stress*

Identification of the response of GmWRKYs to drought/salt stress was based on RNA-seq data collected from a set of drought and salt stress experiments (Tables S5 and S6). Seeds of Williams 82 were cultivated in a 10 × 10 cm flowerpot (vermiculite: nutritious soil is 1:3), fresh leaf of 10-day-old soybean seedlings were used for RNA-Seq.CK1\_treat-Expression represented two independent replicates of plants sampled before any treatment; GH\_treat-Expression related to drought treatment for 5 h (put on the filter paper to simulate drought) of soybean plants at room temperature; CK2\_treat-Expression without NaCl treatment; and NaCl\_treat-Expression salt treatment that soaking soybean roots with 100 mM NaCl solution for 1 h and then sampled for RNA-seq [57,68]. Both log<sup>2</sup> (GH\_treat/CK1\_treat) >1, log<sup>2</sup> (NaCl\_treat/CK2\_treat) >1 and up-regulated were treated as the rule to select GmWRKYs responding to drought/salt stress. Several databases: NCBI (https://www.ncbi.nlm.nih.gov/pubmed), PlantTFDB (http://planttfdb.cbi.pku.edu.cn/), Phytozome (https://phytozome.jgi.doe.gov/pz/portal.html) and SoyDB (http://soykb.org/), were used to annotate Gene ID, Name, Chromosomal localization, CDS, Protein and Group.
