Transcriptional profiling and in silico analysis of Dof transcription factor gene family for understanding their regulation during seed development of rice Oryza sativa L.

Seed development is a complex process controlled by temporal and spatial expression of many transcription factors (TF) inside the developing seed. In the present study, transcript profiles of all the 30 members of rice DofTFs from flowering to seed development stages were analyzed. It was found that 16 Dof genes besides a previously characterized Dof gene 'RPBF' are differentially expressed during the seed development and unlike RPBF are not seed specific. Based on the expression patterns, these rice DofTFs were categorized into four groups-6 genes were constitutive while 4 genes were up-regulated and 3 genes were down regulated and four genes were maximally expressed at specific stages of seed development viz. one gene at flowering, two genes at watery ripe and one gene at milky stage. The involvement of more than one gene at different stages of seed development is suggestive of combinatorial regulation of their downstream genes involved in seed development. In silico expression analysis of wheat and Arabidopsis Dof Tfs also revealed that more than 50% of the Dof genes are expressed during the seed development process. Further in silico study of regulatory elements present in the promoters of these genes revealed the presence of some unique and common motifs in the promoters of rice and wheat Dof genes which indicate that Dof genes are possibly involved in ethylene and jasmonate signaling pathways affecting grain filling and grain quality. These Dof genes containing ethylene responsive motifs in their promoter region could possibly be the targets of recently identified Sub1 gene which codes for a ethylene responsive factor.