LcMYB4, an unknown function transcription factor gene from sheepgrass, as a positive regulator of chilling and freezing tolerance in transgenic Arabidopsis.

Background: Sheepgrass (Leymus chinensis (Trin.) Tzvel) is a perennial forage grass that can survive extreme freezing winters (- 47.5 °C) in China. In this study, we isolated an unknown function MYB transcription factor gene, LcMYB4, from sheepgrass. However, the function of LcMYB4 and its homologous genes has not been studied in other plants.

Results: The expression of the LcMYB4 gene was upregulated in response to cold induction, and the LcMYB4 fusion protein was localized in the nucleus, with transcriptional activation activity. Biological function analysis showed that compared with WT plants, LcMYB4-overexpressing Arabidopsis presented significantly increased chilling and freezing tolerance as evidenced by increased germination rate, survival rate, and seed setting rate under conditions of low temperature stress. Furthermore, LcMYB4-overexpressing plants showed increased soluble sugar content, leaf chlorophyll content and superoxide dismutase activity but decreased malondialdehyde (MDA) under chilling stress. Moreover, the expression of the CBF1, KIN1, KIN2 and RCI2A genes were significantly upregulated in transgenic plants with chilling treatment. These results suggest that LcMYB4 overexpression increased the soluble sugar content and cold-inducible gene expression and alleviated oxidative damage and membrane damage, resulting in enhanced cold resistance in transgenic plants. Interestingly, our results showed that the LcMYB4 protein interacts with fructose-1,6-bisphosphate aldolase protein1 (LcFBA1) and that the expression of the LcFBA1 gene was also upregulated during cold induction in sheepgrass, similar to LcMYB4.

Conclusion: Our findings suggest that LcMYB4 encodes MYB transcription factor that plays a positive regulatory role in cold stress.