Overexpression of wheat C2H2 zinc finger protein transcription factor TaZAT8-5B enhances drought tolerance and root growth in Arabidopsis thaliana.

Main conclusion: TaZAT8-5B, a C2H2 zinc finger protein transcription factor, positively regulates drought tolerance in transgenic Arabidopsis. It promotes root growth under drought stress via the Aux/IAA-ARF module in the auxin signaling pathway. C2H2 zinc finger proteins (C2H2-ZFPs) represent the largest but relatively unexplored family of transcription factors in plants. This is particularly evident in wheat, where the functions of only a few C2H2-ZFP genes have been confirmed. In this study, we identified a novel C2H2-ZFP gene, TaZAT8-5B. This gene shows high expression in roots and flowers and is significantly induced by heat, drought, and salt stress. Under drought stress, overexpressing TaZAT8-5B in Arabidopsis resulted in increased proline content and superoxide dismutase (SOD) activity in leaves. It also led to reduced stomatal aperture and water loss, while inducing the expression of P5CS1, RD29A, and DREB1A. Consequently, it alleviated drought stress-induced malondialdehyde (MDA) accumulation and improved drought tolerance. Additionally, TaZAT8-5B promoted lateral root initiation under mannitol stress and enhanced both lateral and primary root growth under long-term drought stress. Moreover, TaZAT8-5B was induced by indole-3-acetic acid (IAA). Overexpressing TaZAT8-5B under drought stress significantly inhibited the expression of auxin signaling negative regulatory genes IAA12 and IAA14. Conversely, downstream genes (ARF7, LBD16, LBD18, and CDKA1) of IAA14 and IAA12 were upregulated in TaZAT8-5B overexpressing plants compared to wild-type (WT) plants. These findings suggest that TaZAT8-5B regulates root growth and development under drought stress via the Aux/IAA-ARF module in the auxin signaling pathway. In summary, this study elucidates the role of TaZAT8-5B in enhancing drought tolerance and its involvement in root growth and development through the auxin signaling pathway. These findings offer new insights into the functional analysis of homologous genes of TaZAT8-5B, particularly in Gramineae species.