Preliminary Study On The Roles Of Phytochrome B-Regulated Zinc Finger Protein Gene OsTZF1in Growth And Development In Rice

In the previous work, gene profiles were compared between wild-type (WT) and PHYB mutants grown under continuous red light (R) in the GeneChip. One candidate gene encoding CCCH-type zinc finger protein was identified to be down-regulated by phytochrome B (phyB)-mediated R signal. Bioinformatics analyses revealed that the protein encoded by this candidate gene contains plant-unique TZF (tandem zinc finger) motifs. Thus this gene was named as OsTZF1(Oryza sativa tandem zinc finger1).To access the biological functions of OsTZF1gene in rice growth and development, the subcellular localization and expression pattern of OsTZF1were analyzed. OsTZF1protein was found to localize to the cytoplasm using a rice protoplast transient expression system. By comparing the transcript levels of OsTZF1in WT and phytochrome mutants grown in different light conditions, it was found that OsTZF1expression was repressed by phyB-mediated R signaling and not phyA-mediated R signaling. Organ-specificity analysis revealed that OsTZFl mRNA levels accumulated to relatively high levels in leaves and shoots; however, OsTZF1mRNA was relatively low in germinating embryo. These results suggested that OsTZF1might play different roles in the various organs. In addition, the expression of OsTZFl gene in rice was induced by exogenous ABA, but inhibited by JA.To investigate the functional significance of OsTZF1in rice, transgenic rice plants overexpressing OsTZFl were generated. OsTZF1had an effect in regulating the angle between the blade and the leaf sheath in rice. The OsTZF1-overexpression lines had a higher sensitivity to red light with regards to inhibition of coleoptile growth, which indicated that OsTZF1was involved in photomorphogenesis in rice. After analyzing the phenotypes between the WT and the OsTZF1-overexpression lines treated by exogenous ABA or JA, it was found that OsTZF1could be involved in ABA metabolic pathway and response pathway, but not JA. In addition, OsTZF1-overexpression lines exhibited stronger resistance to salt treatment than WT, suggesting an important role of OsTZFl in salt tolerance in rice.Finally, the OsTZF1RNAi expression vector was constructed, in order to comprehensively understand the roles of OsTZFl in phyB-mediated signaling pathway and rice growth and development.