CRISPR/Cas9 mediated gene-editing of transcription factor enhances drought tolerance in soybean ( [L.] Merr.).

The HD-Zip transcription factors play a crucial role in plant development, secondary metabolism, and abiotic stress responses, but little is known about HD-Zip I genes in soybean. Here, a homeodomain-leucine zipper gene designated was isolated. Chimeric soybean plants, overexpressing (), and gene-editing CRISPR/Cas9 () in hairy roots, were generated to examine the gene response to polyethylene glycol (PEG)-simulated drought stress. Bioinformatic analysis showed belonged to clade δ, and was closely related to other drought tolerance-related HD-Zip I family genes such as , , and . The was located in the plant nucleus and showed transcriptional activation activity by yeast hybrid assay. Quantitative real-time PCR analysis revealed that expression varied in tissues and was induced by PEG-simulated drought stress. The showed promoted growth of aboveground parts, and its root system architecture, including the total root length, the root superficial area, and the number of root tips were significantly higher than those of even the non-transgenic line (NT) on root tips number. The better maintenance of turgor pressure by osmolyte accumulation, and the higher activity of antioxidant enzymes to scavenge reactive oxygen species, ultimately suppressed the accumulation of hydrogen peroxide (HO), superoxide anion (O), and malondialdehyde (MDA), conferring higher drought tolerance in compared with both and NT. Together, our results provide new insights for future research on the mechanisms by which gene-editing CRISPR/Cas9 system could promote drought stress and provide a potential target for molecular breeding in soybean.