Expression of MYB transcription factor gene ZmMYB59 affects seed germination in Nicotiana tabacum and Oryza sativa

Background: MYB transcription factors are involved in many biological processes, including metabolism, development and responses to biotic and abiotic stresses. In our previous work, a new MYB transcription factor gene, ZmMYB59 was induced by deep sowing and down-regulated during maize seed germination via Real-Time PCR. However, there are few reports on seed germination regulated by MYB proteins and the functions of ZmMYB59 remain unknown.Results: In this study, to examine its functions, Agrobacterium-mediated transformation was exploited to generate ZmMYB59 transgenic tobacco and rice. In T2 generation transgenic tobacco, germination rate, germination index, vigor index and hypocotyl length were significantly decreased by 25.0~50.9%, 34.5~54.4%, 57.5~88.3% and 21.9~31.3% compared to wild-type (WT) lines. In T2 generation transgenic rice, germination rate, germination index, vigor index and mesocotyl length were notably reduced by 39.1~53.8%, 51.4~71.4%, 52.5~74.0% and 28.3~41.5%, respectively. On this basis, relative physiological indicators were determined. The activities of catalase, peroxidase, superoxide dismutase, ascorbate peroxidase and proline content of transgenic lines were significantly lower than those of WT, suggesting that ZmMYB59 reduced their antioxidant capacity. As well, ZmMYB59 expression extremely inhibited the synthesis of gibberellin A1 (GA1) and cytokinin (CTK), and promoted the synthesis of abscisic acid (ABA) concurrently, which implied that seed germination was repressed by ZmMYB59 in hormone levels. Furthermore, cell length and cell number of hypocotyl/mesocotyl in transgenic tobacco and rice were notably decreased. Conclusions: Taken together, it proposed that ZmMYB59 plays a negative regulatory role during seed germination in tobacco and rice, which also contributes to illuminate the molecular mechanisms regulated by MYB transcription factors.