Wheat transcription factor TaSIP1 participates in plant response to osmotic stress and abscisic acid.

Environmental stresses, including drought and high salinity, induce osmotic stress that severely impairs plant growth and agricultural productivity. TaSIP1, a membrane-associated NAC transcription factor interacting with TaSRO1 (Triticum aestivum Similar to RCD-one 1), participates in salinity responses through mitochondria retrograde signaling. Here, we report a critical role of TaSIP1 in osmotic stress as well as abscisic acid (ABA) signaling in wheat and Arabidopsis (Arabidopsis thaliana). TaSIP1 was downregulated by polyethylene glyco (PEG), dehydration and ABA. TaSIP1 overexpression in both wheat and Arabidopsis exhibited hypersensitivity to osmotic stress and ABA during early seedling growth, whereas RNA interference (RNAi)-mediated knockdown wheat lines displayed the opposite phenotype. In the presence of ABA or osmotic stress, the transcript levels of ABA biosynthesis and signaling related genes increased in TaSIP-overexpressing transgenic Arabidopsis plants. TaSIP1 activated the transcription of ABA Deficient 2 (ABA2), ABA3, Sucrose Non-fermenting 1-Related Protein Kinase 2.2 (SnRK2.2) and ABA Insensitive 5 (ABI5) genes in Aradidopsis, and TaSRO1 attenuated the transactivation activity of TaSIP1. Notably, TaSIP1-overexpressing transgenic Aradidopsis plants showed reduced cellular ABA levels and downregulated stress-responsive gene expression. These findings establish TaSIP1 as a key regulator of osmotic stress responses, acting through the modulation of ABA signaling pathways.