Generation of Wheat Transcription Factor FOX Rice Lines and Systematic Screening for Salt and Osmotic Stress Tolerance

<div><p>Transcription factors (TFs) play important roles in plant growth, development, and responses to environmental stress. In this study, we collected 1,455 full-length (FL) cDNAs of TFs, representing 45 families, from wheat and its relatives <i>Triticum urartu</i>, <i>Aegilops speltoides</i>, <i>Aegilops tauschii</i>, <i>Triticum carthlicum</i>, and <i>Triticum aestivum</i>. More than 15,000 T₀ TF FOX (<u>F</u>ull-length cDNA <u>O</u>ver-e<u>X</u>pressing) rice lines were generated; of these, 10,496 lines set seeds. About 14.88% of the T₀ plants showed obvious phenotypic changes. T₁ lines (5,232 lines) were screened for salt and osmotic stress tolerance using 150 mM NaCl and 20% (v/v) PEG-4000, respectively. Among them, five lines (591, 746, 1647, 1812, and J4065) showed enhanced salt stress tolerance, five lines (591, 746, 898, 1078, and 1647) showed enhanced osmotic stress tolerance, and three lines (591, 746, and 1647) showed both salt and osmotic stress tolerance. Further analysis of the T-DNA flanking sequences showed that line 746 over-expressed <i>TaEREB1</i>, line 898 over-expressed <i>TabZIPD</i>, and lines 1812 and J4065 over-expressed <i>TaOBF1a</i> and <i>TaOBF1b</i>, respectively. The enhanced salt and osmotic stress tolerance of lines 898 and 1812 was confirmed by retransformation of the respective genes. Our results demonstrate that a heterologous FOX system may be used as an alternative genetic resource for the systematic functional analysis of the wheat genome.</p>