NtGRAS-R1, a topping responsive transcription regulator in tobacco roots

Topping, the critical cultural practice, is a kind of damage occurred tobacco shoot, which can obviously promote roots growth. Up to now, the mechanism regulating roots growth after topping is still unclear. In our previous works, miR171d was identified as a major topping responsive miRNA in tobacco roots, and its target gene was predicted to belong to the GRAS gene family. In the present study, NtGRAS - R1 , a novel GRAS transcription regulator, was firstly cloned from tobacco roots. NtGRAS-R1 contained an open reading frame of 1527 bp encoding a 508-amino acids protein, and its molecular mass and isoelectric point was 56.199 KD and 5.24, respectively. GRAS proteins in tobacco can be grouped into nine subfamilies, including HAM, SCR, LAS, DLT, DELLA, SCL, LISCL, SHR and PAT1. NtGRAS-R1 is highly homologous with NtGRAS44 and belongs to HAM subfamily. The expression of NtGRAS - R1 can be detected in tobacco roots, leaves and stems, and its expression level was highest in tobacco roots. The analysis of transgenic tobacco showed that NtGRAS - R1 was involved in several biology processes, such as rooting, germination and root development, which will be helpful to explore the roles of NtGRAS - R1 in response to tobacco topping.