OsTZF1, a CCCH-tandem zinc finger protein, confers delayed senescence and stress tolerance in rice by regulating stress-related genes.

OsTZF1 is a member of the CCCH-type zinc finger gene family in rice (Oryza sativa). Expression of OsTZF1 was induced by drought, high-salt stress and H(2)O(2). OsTZF1 gene expression was also induced by abscisic acid (ABA), methyl jasmonate (MeJA) and salicylic acid (SA). Histochemical activity of β-glucuronidase (GUS), in transgenic rice plants containing the promoter of OsTZF1 fused with GUS, was observed in callus, coleoptile, young leaf and panicle tissues. Upon stress, OsTZF1-GFP localization was observed in the cytoplasm and cytoplasmic foci. Transgenic rice plants over-expressing OsTZF1 driven by a maize ubiquitin promoter (Ubi:OsTZF1-OX) exhibited delayed seed germination, growth retardation at the seedling stage and delayed leaf senescence. RNAi knocked-down plants (OsTZF1-RNAi) showed early seed germination, enhanced seedling growth and early leaf senescence compared to controls. Ubi:OsTZF1-OX-OX plants showed improved tolerance to high-salt and drought stresses and vice versa for OsTZF1-RNAi plants. Microarray analysis revealed that genes related to stress, reactive oxygen species (ROS) homeostasis and metal homeostasis were regulated in the Ubi:OsTZF1-OX-OX plants. RNA binding assays indicated that OsTZF1 binds to U-rich regions in the 3'-UTR of mRNAs, suggesting that OsTZF1 might be associated with RNA metabolism of stress-responsive genes. OsTZF1 may serve as a useful biotechnological tool for the improvement of stress tolerance in various plants through the control of RNA metabolism of stress-responsive genes.