Expression Analysis And Functional Characterization Of IDD Family Transcription Factors In Rice Roots

Rice is not only the important model of monocotyledon plants, but also the most important food crop in our country. There are many natural calamities every year, including drought, waterlog and salinization of soil. These environmental fluctuations directly influence the growth of rice roots, and have induced great loss of rice yield. Thus, it is necessary to learn how rice roots develop, and use the information and knowledge obtained from our root studies to breed new anti-calamity rices with improved root system.My study was based on the studies of roles of IDD family transcription factors in Arabidopsis root development. I performed expression analysis and functional characterization of IDD family transcription factors in rice, through promoter fusion, over-expression, gene knock-down and bioinformatic approaches. Besides, we screened enhacer-trapping rice lines carrying the GAL4-UAS two component system, to dicover new genes related to IDD family transcription factors.This results of my study are the follows.1. We generate promoter fusion lines to analysis the express pattern of IDD family transcription factors in rice. And we found IDD2, IDD7, IDD9 and IDD12 are all express at the xylem of steles. GUS expression was also observed from the meristem zone to the maturation zone in both IDD2 and IDD7. However, IDD9 and IDD 12 only exist upon the elongation zone. Besides, IDD7 expresses at the epidermis, cortex and endodermis.2. We generated both over-expression and knock-down amiRNA transgenic rice lines for comparison. We found that amiRNA seedlings had thicker root diameter than the Wild Type control of IDD12; whereas slightly thinner roots were observed in the over-expression lines when compared to the Wild type. Thus, IDD 12 may control the diameter of rice roots. And we observed that the cortex cells became bigger in the cross section.3. We screened the enhancer trap lines and found a line with GUS expression at the third layer cells in the meristem zone. These cells will have fibrosis in the elongation zone and become sclerenchyma. We found four genes next to the T-DNA insertion site through adapter-PCR, but we have not confirmed the candidate gene yet.