bHLHTT8 Transcription Factor from Sorghum Restores Brown Seed Coat in tt8 Arabidopsis Mutants

A. SALEZ; M.V. RODRIGUEZ; M.L. FALCONE FERREYRA; P. CASATI; S. RIUS

Congreso; LIV Reunión SAIB 2018; 2018

Sorghum [Sorghum bicolor (L) Moench.] is one of the most important cereals cultivated in the world. The pre-harvest sprouting, due to aninadequate establishment or maintenance of seed dormancy, is responsible for high yield losses. Flavonoids are secondary metabolites with widebiological functions described in plants. Different evidences suggest that their accumulation in the seed coat could be involved in theestablishment and maintenance of dormancy. Thus, this research aims to elucidate the biological roles of the putative bHLH-SbTT8 transcriptionfactor (TF) from sorghum and its contribution in the flavonoid biosynthesis. We generated Arabidopsis transgenic plants expressing thistranscription factor under the control of CaMV35S in the background tt8 (mutants in transparent testa 8, the orthologous gene of SbTT8,35Spro:SbTT8). SbTT8 TF partially complemented the flavonoid deficiency of tt8 mutants in seed coats. By vanillin assay, transgenic plantsshowed proanthocyanidins accumulation in immature stages of transgenic seeds. Moreover, when dormancy was studied by calculating thegermination index and the mean germination time, 35Spro:SbTT8 plants exhibited an intermediate behavior between tt8 mutants and the WildType Col-0 (higher levels than tt8 mutants, but lower than WT plants). In addition, in root tips of Arabidopsis plants expressing SbTT8 fused toGFP, SbTT8 localized primarily in the nucleus, although faint fluorescence was also detected in the cytoplasm, consistent with its predicted roleas a transcription factor.