New insights into the complex and coordinated transcriptional regulation networks underlying rice seed development through cDNA chip-based analysis

Transcription factors (TFs) are major, crucial factors for developmental control. To elucidate the effects of TFs on rice seed development, we generated a cDNA chip containing 325 rice cDNA clones, which are from flowering stage and encode known or putative TFs belonging to 12 different families, and used this chip for expression profiling at 8 continuous seed developmental stages. The results showed that in comparison to their expression in mature leaves, a total of 135 TF genes were preferentially transcribed in seeds. Cluster analysis based on the temporal expression patterns grouped them into 12 types, each of which contained members of various families showing common unique expression patterns. The results provide insights into possible key roles for members of several TF families during seed development. In addition, the expression patterns of these genes were examined in vegetative tissues including roots, seedlings and stems, as well as in 2-week-old seedlings following the application of plant hormones or abiotic stresses. The results showed that many of the seed-preferential TFs were also involved in hormone and/or abiotic stress effects, suggesting the potential existence of uncharacterized transcriptional networks, or cross talk between hormone and abiotic stress signaling and seed develolpment. Furthermore, analysis on the cis-elements locating in promoter region of seed preferential TF genes suggested that Dof proteins play essential roles in hierarchical regulation of gene expressions during rice seed development, which, taken together, provided informative clues for elucidation of the molecular mechanisms of transcriptional regulation and signaling networks in the complex developmental processes of rice seeds.